Saturday, February 26, 2022

Apple II video to HDMI using a Raspberry Pi Zero / Pico



Example output from an Apple II video to HDMI adapter that I have been toying with. Pictured is one of the many colour models. The dual colour mode represents how the Apple II's video is inherently monochrome and yet the use of artifact colour results in a decent colour depth for such a small storage footprint.

In September 2021, Rob, a fellow Apple II enthusiast posted some images of an RGBtoHDMI, a Raspberry Pi based HDMI video solution, being setup on his Apple II. It sparked my interest because back in 2015 I looked into using the Raspberry Pi as a HDMI video display solution. This was around the time I was working on the "A2 Video Streamer" project. I couldn't see how the Raspberry Pi could capture signals consistently and fast enough to process the A2 video stream so I implemented a solution using the BeagleBone Black instead. Even though my devices worked, neither of them were user friendly enough to warrant further development. I don't see these projects as failures but as learning opportunities and stepping stones to bigger and better solutions. The RGBtoHDMI has given me new ideas to investigate.

The RGBtoHDMI is an amazing project. (https://github.com/hoglet67/RGBtoHDMI/wiki) It began as a HDMI interface for the BBC Micro but because of its flexibility it has been modified to support many computer systems of the same era, including the Apple II and the Apple IIGS. It's made up of two main parts. One being the CPLD which handles the level shifting, digital or analog signal sampling and the bit shifting while the Raspberry Pi Zero handles the pixel clock and frame image generation. It generates the right frequencies that allow it to synchronise to a computer's video clock. However, this comes at a price. It pretty much maxes out the RPi Zero's CPU. Even though it can output Apple II video to HDMI, using this device for the Apple II, in my opinion, is not overly efficient (I'm talking about the TTL signals here and not the composite one). The Apple II provides its own pixel clock so the majority of RGBtoHDMI's awesomeness, in this situation, is not needed. Instead, I would prefer to use the RPi Zero's CPU resources to perform better video emulation. The source code for RGBtoHDMI is huge and complex. I wanted to take a more simplistic approach.
        


Raspberry Pi Zero being used for video output and a few of the many failed attempts at getting a stable picture.

I wanted to revisit the Raspberry Pi to see if it was capable of being a simple modern day Apple II video solution. Especially now with the tiny size of some Pi models. I started off by using the RPi Zero to sample Apple IIc video signals directly (after going through level shifting of course). To get the maximum amount of power available out of the RPi Zero, bare metal programming was used. Not true bare metal. The manufacturer's firmware is still being used to setup the communications and the video but then everything after that is bare metal. Even then, using the general GPIO interface, I wasn't able to obtain a stable picture. I tried running the program in C, in assembler (manually optimised), using DMA and even running the code on the Video Processing Unit (VPU) but with no luck. The Apple II pixel clock being just above 14MHz means that sampling needs to be performed at around the 30 mega samples per second mark. I was getting in the high 20s but the readings were not consistent. We have a situation where the Apple II is outputting the video stream at a consistent rate but the RPi Zero only wants to read the data when it feels like it. The RPi Zero is not a microcontroller. It's a computer and the GPIO is isolated from the CPU. This means that it is difficult to control high speed parallel data coming in. In most situations the RPi Zero will be the master and dictating when and how the data is being transferred. We don't have that luxury here so a new plan was needed.

Digging deeper into the RPi Zero, there is an interface which shows potential as a high speed parallel means of reading in data. That interface is the RPi's Secondary Memory Interface (SMI). There isn't a lot of documentation on the interface or example projects, especially when it comes to bare metal. However I did find enough to get me started and plenty to keep me experimenting. The worst part of this interface is that the bus is driven when it's not active. This is to protect memory chips from having floating pins, which is not good for them. However, we are not interfacing with memory chip but an Apple II video source instead. The consistent Apple II video stream doesn't fit in well with this interface. I needed to find something to isolate the two. At first I was concerned about the SMI shorting out the Apple II motherboard but I found a great solution. The 74HCT4066 chip worked quite well as an isolator. This is an analog switch which has a small amount of "on resistance" that allows this chip to be used as a level shifter. Also the chip's control lines were used to isolate the Apple II video signal when the SMI interface drove the data bus. I did manage to pull in data at speeds of 15 mega samples per second but for some reason it would not work at the higher speeds. At that point, my wired connections between the IIc and the devices were a mess and not as short and organised as they are shown in the photo above. I wasn't surprised I had issues. Frustrated with not being able to get anywhere with the project I took a break. Time was running out for the year and I wasn't going to lug my development machine with me on holidays. Any more work in this area was going to have to wait until the following year.



Raspberry Pi Pico and a HDMI breakout board being used for video output. Monochrome output.

What I did have with me was my laptop and the Raspberry Pi Pico which I wanted to try out. I was able to quickly and easily setup a development environment for the RPi Pico which allowed me to play around with video examples over the holidays. When I returned back home, it only took me a weekend to get the RPi Pico working as a video output device for the Apple IIc. The RPi Pico is a totally different beast compared to the RPi Zero. It's a microcontroller and is able to control the GPIO pins at the same rate as its system clock, which is rated to 133MHz. This A2 video solution is based on top of the PicoDVI project (https://github.com/Wren6991/picodvi). It uses a HDMI socket but the signals are actually DVI signals. These DVI signals are being bit banged out of the RPi Pico in a semi-compliant format. It's amazing that this actually works since DVI and HDMI are normally reserved for devices that run ten times the speed of the RPi Pico or have dedicated hardware. This solution has several drawbacks. The RPi Pico needs to be overclocked to 252MHz for a 640x480 60Hz picture and even more if you want higher resolutions. Also, due to not being fully DVI compliant means that working on a given monitor is just pot luck. I found that a monochrome picture worked well but I could not get any colour examples working properly on the holiday apartment's TV or my home DELL monitor (even after trying the recommended work arounds). I'm sure I could have found a monitor to make this work but I just didn't see this as a solution we could move forward with. That's not to say the RPi Pico is not useful. Using the RPi Pico as an Apple II to VGA adapter would be a better alternative. There are several projects around which demonstrate the RPi Pico's ability to generate VGA signals. The RP Pico's VGA output would need to be RGB565 (16bit colour) since there are not enough pins on the Pico to directly make an RGB888 (24bit colour) solution. Maybe you could but with more hardware. However, using a common Apple II colour palette (https://docs.google.com/spreadsheets/d/1rKR6A_bVniSCtIP_rrv8QLWJdj4h6jEU1jJj0AebWwg/edit#gid=1819819314) fits in perfectly into the RGB565 colours.

Taking it to the next level will require RGB888 (24bit colour / 16 million colours) and a lot of processing power for colour emulation. That's why I moved back to working with the RPi Zero. Again I tried my luck with the SMI interface and yet again I fell flat on my face. Getting SMI working with DMA and bringing in the data at a paced rate would be the ultimate goal. This would leave the RPi Zero totally free to do just one job ie colour emulation. To get a working solution in the meantime meant that I had to compromise. I figured I could get something operational now and then later work backwards to achieve the ultimate result.

Logic analyser output showing one line of an Apple II video signal. Things to note.
1. The clock (14M) is too fine to make out using this scale. Only after zooming in would you see a nice square wave.
2. The start of line can be determined by using the SYNC or WNDW signals.
3. The GR signal goes from high to low indicating that the previous line was a graphics line but the current line is part of the text section. The Apple II screen is in MIXED mode ie graphics and text.

Before leading into the working solution I just wanted to express how simple the Apple II video stream really is. There are three signals which give you most of what is needed for a video display. The most important of the signals is the serial data out (SEROUT) which carries the monochrome 560 pixels per line of the Apple II screen. All the Apple II video display modes are a subset of the 560 pixels. Then there is the clock (14M). Its frequency is just over 14 MHz. It does not matter that the frequency of the US version is slightly different to the PAL version because the only thing needed for processing is the clock's edge. The third signal is used to calculate the horizontal and vertical line synchronisation. The sync (SYNC) signal can be used for this if you want to start at the very left of the screen, including blank padding, or the window (WNDW) signal which starts just before the 560 Apple II pixels. The vertical sync can be determined by reading the specific sync pattern or just by measuring the time between sync pulses. Other less important signals can be used to make the display cleaner. For example the GR signal can be used to kill the colour for lines that are displaying text (this removes the colour and makes text look clear and sharp). The LDPS signal can be used to re-align different video modes. The number of line pixels is always 560 but some video modes start closer than others to the left hand border.


Raspberry Pi Pico and Pi Zero being used for video output. 


Example of different monochrome and colour modes. The colour mode shown here is what the AppleWin emulator calls "Composite Idealized". The last mode fades the picture in and out but obviously the processing power needed is not enough using the current setup.

A working video solution was generated by using a RPi Zero and a RPi Pico. The RPi Pico acts as a serial to parallel converter and a buffer which stores data until the RPi Zero is ready to read that data. This means the RPi Zero's GPIO does not have to operate at a high speed. I would have preferred to have used a hardware serial to parallel FIFO but I just couldn't find anything that was cheap and available in a DIP package. In its current configuration the RPi Pico is not even working up a sweat. Only one PIO module is operating which means that the other PIO module and the two CPU cores are not being used. An 8 bit bus was enough to get this device to work. I was considering going to 16 bits but then I would loose the serial port debugging pins. Also, the archaic RPi Zero GPIO pin numbering makes routing PCB tracks more difficult. So, less bus lines in this case may be better. The GPIO is being called directly and for now, it is not using the SMI interface. Eight pixel bits are being read and processed on the fly before being sent to the frame buffer. Since the bitstream always represents a monochrome picture, emulation is needed to convert this into colour information. I'm experimenting with several different colour models and pushing the limits to see how much processing power can be used before the video picture turns to shit. At the moment the data from the RPi Pico is being polled which is a very inefficient way of doing communications. Even before going to the ultimate DMA solution, I could rewrite the code to be interrupt or state driven to get more out of the system. There are several other simple patches that could be done to increase performance like adding a bigger buffer in the RPi Pico or adding buffering to the RPi Zero (this would allow for processing during the blanking times). However then you start to compromise between the video delay and the emulation quality. For now I'm just happy that it works.

The adapter can be developed into a package for the IIc using the IIc's unique video port, the IIe using the 60pin auxiliary port or for the older Apple II models using the fiddly method (that's the technical word for it) by using alligator clips and connecting directly to chip pin legs (like in a2heaven's "Apple II VGA Scaler" card). A lot of the code is currently hard coded since the aim was to concentrate on getting a working system. It's currently operating in the centre of a 640 x 480 frame running at 60Hz and using ARGB8888. The A2's horizontal resolution is doubled and the second line is illuminated or turned off depending on the scan line display setting. I've added two user buttons. One button toggles the different display modes and the second button toggles between the colour palettes of which I only have two setup. I love how user friendly this solution is. Plug it in and it's up within two seconds. Most of that time seems to be due to the monitor syncing up. I did consider doing an FPGA implementation instead. I purchased a Scarab FPGA with HDMI outputs a few years back but I never got around to doing anything with it. It wasn't exactly cheap and they don't look to be available anymore. There are cheaper FPGA alternatives around today like the "Tang Nano 4K" which looks promising (I have one on order). So, is this going to be the best Apple II video solution? Definitely not. I still prefer to use a CRT when I can. When a CRT is not available then I love the VidHD, especially as a IIgs solution. All I wish is that we can make a device with great colour emulation for the HDMI platform that is cheap, easy to make and is readily available. Making a VGA version may not be a bad idea either. As a DIY project I couldn't think of anything simpler. The bonus is that if you don't like any of my colour models then you'll have the option to re-program the device and display whatever suits you.

Video of the device going through its current display modes. They come in pairs. Every second one is the same as the one before except it is set to have 50% scan lines. https://docs.google.com/open?id=18Pt6o6ZSSOQmiXkR6-xle7y614uFe4Pn

Saturday, October 2, 2021

Game Controller - AppleWin - Added support for 4play and SNES MAX cards


 
 
AppleWin, the dominant Apple II emulation software for the Windows platform, from version 1.30.5.0 now supports the 4play and SNES MAX joystick cards. Thank-you to Tom and Nick (long time AppleWin developers) for helping me get this feature into the software.

Gamers now have the opportunity to play games such as "Attack of the PETSCII Rebots" which only supports the SNES MAX or a keyboard for user input, on an emulation platform with alternate controllers. A great option for those who do not have access to the physical joystick cards.

This also gives developers an easy way to help out with developing software for these cards. I use AppleWin quite a lot for debugging and this is going to save me a great deal of time. It will also help me with not having to lug around an Apple II development system on my family vacations.



In the AppleWin Configuration page the "Input" tab is used to set the availablity of the required card in either slot 3, 4 or 5. A "PC Controller" needs to be connected to the PC. AppleWin will automatically detect the "PC Controller" (this is independant to what is selected for Joystick1 and Joystick2 on the configuration page). Some game controllers have different mappings for their buttons so the most generic mapping has been setup as default but alternate mappings can be accessed via command line switches.

The latest version of AppleWin can be obtained from here :- https://github.com/AppleWin/AppleWin/releases

Friday, September 10, 2021

Game Controller - SNES MAX - Software Resource


Just like the 4Play joystick card, I have setup this software resource page to keep together a list of supported SNES MAX software titles. I'll add more to this list as they become available.

Program(s) SNES MAX adaptation/conversion by SNES MAX port usage Comment Links
Attack of the PETSCII Robots David Murray / Ian Brumby 1 http://www.the8bitguy.com/26654/petscii-robots-for-apple-ii-now-available/
Robotron 2084 Nick Westgate / Lukazi 1 https://docs.google.com/open?id=1QYYS0s5PkIrQ3G0R3xiGGfYnjJvZ-FFe
Mario Bros Lukazi 1 & 2 Two player co-op. https://docs.google.com/open?id=1QYYS0s5PkIrQ3G0R3xiGGfYnjJvZ-FFe
XSlinger HD Jay Craft 1 & 2 Two player, Asteroids inspired. Interesting use of VidHD's text mode for graphics.
Requires Apple IIGS w/2 MB RAM and VidHD card.
Video: https://youtu.be/6RZ3r3NXTpg
Download: https://github.com/01craft/xslingerHD/releases

Friday, June 25, 2021

Game Controller - SNES MAX - SNES Controller to Apple II Serial Interface Card



The SNES MAX Cable and the SNES MAX Socket.

What is it?

The SNES MAX is a serial interface card that allows an Apple II to communicate with SNES Controllers. It allows a slotted Apple II to read the maximum number of the SNES controller pushbuttons ie all twelve of them. The game "Attack of the PETSCII Robots", developed by David (the 8bit guy) makes use of all twelve buttons. It allows you to do cool stuff like move in one direction and fire in another (which you want to do when being chased by a pesky robot). This game only supports keyboard or SNES MAX control. Ian led the Apple II conversion effort of the PETSCII Robots game and commissioned me to make an SNES adapter, similar to what was done for the Commodore version.

The PETSCII Robots game conversion overlapped the development of the SNES MAX. It's unfortunate that the SNES MAX was not able to be completed in time for the game release (you need to run PETSCII Robots V1.1 or above for the card to work). While putting the first batch of production cards together I also converted a two player game, Mario Bros, to test and make use of SNES MAX's dual controller ability, These are the only software titles currently providing support for the card but we hope other developers come on board and help add more titles. There are a few games I have on my radar which I hope to convert some day. Other great candidates include the recent work to convert the "Game Boy" Tetris to Apple II conversion. By using an SNES controller you can closely resemble the "Game Boy" controls and capture more closely that specific controller feeling. Another great game, Roborton 2084, could use a controller upgrade. Its Apple II version resulted in a gameplay downgrade. The arcade version uses two joysticks, one for movement and one for the shooting direction. Much like the PETSCII Robots game, it could really benefit from having these independent actions. There are many other keyboard based Apple II games where the joystick control was not implemented or was cumbersome to use.

Let's be clear. The SNES MAX is not an Apple II joystick replacement. It does not operate via the Game Port. The SNES MAX uses the SNES controller protocol which reads the controllers serially just like how it's done on an SNES Console.

The SNES MAX comes in two different board layouts (the cable version and the socket version). Both boards are electrically identical. The difference lies in the connection options. The cable version of the board would suit users that predominantly would use wired SNES controllers and the socket version would suit those who plan to use a wireless solution. Either board can be used with wired or wireless controllers. The sockets allow for a cheaper solution but it means that if you are using wired controllers then the plugs will not fit through the back Apple II case slots (unless used on the early Apple II models where the back slots are open) and you will need to keep your hood open.



Things to note:
1 The wireless receivers may consume a lot of power eg the 8BitDo receivers consume about 100mA on the 5V rail. When using multiple receivers or if your system is already highly loaded you may experience power issues. Make sure you use the SNES MAX appropriately based on your power supply and existing card setup.
2. The SNES MAX Socket version results in a tight fit between slots if you have the following Apple II slot populated. Wireless receivers which are larger in physical size than the 8BitDo option may cause issues.
3. The 8BitDo receiver tends to have a very tight plug fit with the SNES sockets. I'm told this is also the case when using the 8BitDo receiver on an original SNES console.
4. The SNES MAX only works with digital signals. Even though some wireless controllers may have analog thumb sticks, the analgue signals are not used. For example the 8BitDo wireless receive converts the thumb stick 1 into the digital direction buttons while thumb stick 2 is not used.
5. Other SNES devices such as guns and multitaps are not supported. Mice may work.

The SNES MAX has been tested using an Apple IIe and a IIGS. Various different revisions of the wired controller and 8BitDo's SNES wireless receivers have been tested. Also all controllers have been tested with a lengthy extension cable.


How it works.

Early 8bit game consoles like the Atari 2600 use joysticks where each button or direction is wired directly to the game console ie parallel communications. With the advent of faster consoles and the requirement for more pushbuttons on the controller, multiplexing was selected over more signal lines (needing bigger plugs and thicker cables). This resulted in the transfer of more signal data over fewer lines ie serial communications. Some controllers try to be backwards compatible with the Atari standard like the Amiga CD32 which is half parallel and half serial and the SEGA Genesis / Mega Drive Controller which is both parallel and serial depending on a selected mode. The following generation (6 button) SEGA Genesis / Mega Drive Controller is backwards compatible and so the controller became an overly complicated solution. Alternately Nintendo's solution for its original game system, the NES, only uses serial communications which results in a very simple and elegant design. For its following generation, the SNES controller, is just an extension of this which is also nice and simple. The SNES controllers are one of the simplest of serial controllers to work with. Hence their preference over alternate controllers.



The way in which an SNES controller works is by using simple latch chips ie 2x4021, 2xW545 or 1xV520B (the NES controller only used one 4021 chip). Only three signal lines are needed between the host and the controller. A latch signal is sent from the host to the SNES controller to tell it to take a snapshot of all its pushbuttons. Then the data line is read by the host to determine if a button is on or off. Clock signals are sent from the host to the controller to tell it to send the next button press status. This results in being able to read up to sixteen digital button signals. However, the controller is physically constricted to only using the first twelve of these signals. There may be third party controllers which make use of the extra four spare buttons.

On the host side (in this case the Apple II) software needs to be written to read the SNES controller data serially. This routine takes about 500 microseconds (for two controllers ie twelve pushbuttons read from each controller) which is much quicker than the roughly 3000 microseconds it takes to read one of the Apple II analog joystick axis. You then have code on top of that which processes the data but you have to do that anyway regardless of which type of interface you have. Example software for the serial import routine can be found in the attached file at the end of this blog post.


Designing the solution.

The first decision was to select which type of interface this project was going to take. The options were

1. Remove the existing cabling out of a SNES controller and wire the twelve pushbuttons directly to a parallel input card (such as the 4Play card). The problem with this solution is that it requires the destruction of the original controller.

2. Build a buffer in between the SNES Controller and a parallel input card (such as the 4Play card). A microcontroller could be used to buffer the pushbutton signals and push these in parallel to the host. This option requires more hardware but simpler software on the Apple II side. The problem with this option is you would need two devices, the adapter and a parallel interface card. These days using a microcontroller to do the buffering is the cheapest option however back in the day this was not the case. The December 1993 copy of Popular Electronics (http://www.americanradiohistory.com/Archive-Poptronics/90s/93/PE-1993-12.pdf), starting at page 34, contains a great article on how this was achieved back in the day.

3. The serial ports on an Apple II (directly from the IIc/IIGS ports or via a serial card) use a different type of serial communication compared to that of the SNES Controller, both in electrical terms and in the terms of the protocol. A microcontroller could be build inbetween to buffer the signals and then serially send them to the host. This would involve a considerable amount of work on the hardware side and the software side.

4. Talk serially directly from the host to the SNES controller. This requires very simple hardware and relatively simple software. Hence this option was chosen for the project. There is always a trade off between designs and in this case, when comparing this solution to the parallel interface option we are sacrificing the speed of reading the data (500 microseconds instead of 40 microseconds) and in doing so make the hardware side much, much simpler. This was deemed an acceptable trade off and fits in well with the ethos of how the Apple II was designed ie optimise the hardware and let the programmer deal with what they get.

Once the type of interface was selected there were two main ways in which this could be implemented. One was to use the 16pin Game Port interface (not the 9pin Game Port because it needs to support output as well as input signals) and the other was to use the slot based interface.

I love the 16pin Game Port as a quick and easy way to do hobby experiments. However, for a durable professional solution I believe that using the Apple II slots is a much better option. I find the 16pin Game Port fiddley and difficult at times to connect in to. It's not something I would want to be plugging to and unplugging from all the time. The SNES controller adapter which uses this interface has been around for decades (https://rich12345.tripod.com/nintendo/nintendo.htm) however one must take care in its design because other circuits use this socket too (shift key mod, open and close apple buttons / joystick PB0 and PB1) meaning if diode protection is not added one can easy cause a short circuit which would not be good for the motherboard. Being such a simple build I did put it together just for laughs. It does work however it does have its issues ie CMOS - TTL theoretical incompatibility, problematic when used with certain controllers (due to region locking) and control-resetting the Apple II due to the open/close apple button tie ins.


Just a few of the official SNES Controller boards. Here are several of the SNES MAX boards used for testing.

For a durable solution, using the slot interface is definitely the way to go. I figured that being such a simple design that I could knock the project over in a day or two. Here we are a few months down the track and I'm finally getting the production boards ready for sale. It's annoying to think how much work there was for such a simple circuit. Most of the delays have come from having to wait for parts and PCBs. I have managed to get every prototype board working however they have not worked in all conditions.

I've never owned an SNES console, therefore, I've never had an SNES controller. Acquiring one was my first step in testing the first prototype. The testing went fine until I found out that Nintendo had not only region locked specific sections of their console but also region locked the controllers. It surprised me to find out how many variations there are of just the official SNES controller circuit boards. For proper testing I needed to source the other types of controllers which I did. The difference in electronics between the US/JAPAN controller and the PAL controller was not very much (pull up resistors on the latch and clock lines) but it was enough to cause issues with the first prototype. Being a tri-state design with pull-ups/pull-downs caused issues because of the region locking differences. Running the controllers via extension cables or when using two controllers at the same time exacerbated the issue. Swapping both the chips to their inverted equivalents meant keeping the same design but having an extra inverter to replace the pull-down latch circuit. This worked but the design was changed anyway to remove the need for tri-state outputs altogether and resulted in a more stable solution.

Measured resistance between 5V and the following lines
US/JAPAN, Model SHVC-005, Design 1990, Clock = 7.3k ohm, Latch = not connected.
US/JAPAN, Model SHVC-005, Design 1992, Clock = 12.8k ohm, Latch = 12.9k ohm.
PAL, Model SNSP-005, Design 1990, Clock = 1.0k ohm, Latch = 3.6k ohm.
PAL, Model SNSP-005, Design 1992, Clock = 1.1k ohm, Latch = 2.4k ohm.
8BitDo Bluetooth Wireless Receiver, Clock = 153.9k ohm, Latch = 153.2k ohm.

This design worked on my ROM1 IIGS and IIe machines but did not work on Ian's ROM3 IIGS. The wired SNES controllers would work but the wireless controllers would not. I tried to setup my IIGS as close as possible to Ian's and even tried his wireless controllers but I could not reproduce the problem. Luckily Ian had a logic analyser and hence was able to provide me with details as to what was going on. We tried a number of changes but to no avail. Having to do remote testing is never easy.

At this stage I started looking more closely at the chip design. The SNES controller is CMOS based and I had been using TTL logic to match the Apple II slots. Signals going from CMOS to TTL are not an issue but going from TTL to CMOS requires greater care. Technically the signals are not compatible and the adapter was only working for me because my TTL chips were manufactured to better tolerances than what the TTL requirement specifies. The right move was to change over to using 74HCT chips instead of the 74LS ones. With this comes extra care since CMOS chips are more prone to static damage. It was decided to include some protection circuitry. No so much to reduce electrical noise or to improve static immunity but mostly to protect the adapter from issues caused by hot plugging of the controllers.



I went back over the Apple II circuit diagrams using several different publications and I came across the signal descriptions that show that during a data output pulse video garbage can be super imposed into the first part of the pulse. I kicked myself for not knowing this. Normally this would not have been a problem since latching circuitry only looks at the pulse during the low to high Apple II clock transition and does not take the rest of the pulse into account. In our case there was no latching circuitry (the latch and clock pulses are being generated by the Apple II system clock and not by any latching chips). I find it strange that I could not reproduce these issues on any of my machines. The adapter design was changed from using the data bus to the address bus for control and this fixed the issue.

Could this design be optimised even further? Definitely. Daniel put forward some great alternative designs including a single chip version and designs where the address bus control was not required ie the clock and the data read actions could be joined together into one action. These designs do work, however, because of the tri-state design it had stability issues just like my first prototypes. Tuning could have been performed but at the expense of other factors such as a larger current draw. The issue with joining the clock and data read actions resulted in the Apple II latching the button read data on the same pulse transition as the change between buttons. It was deemed to risky to use a design that's working on the very edge of what is possible.

Just as I was putting together the first run of boards and performing unit testing, I found that a specific combination of controllers would not work together. Each controller was fine on it's own but since the clock and latch signals are shared between two controllers, a controller can affect the signals going to the other controller. The region locking issue had come back to haunt me. This time thanks to the addition of the protection circuitry. Luckily the fix did not required a PCB board change. However, I had to purchase extra controllers to perform more thorough testing and this just delayed the project even further.

I'm happy to be finally releasing the product.


Availability and distribution.

I've only just received the production boards and have put a few together to get some photos for this blog entry. I've started putting together the first run of boards as the component parts arrive. The boards will be available shortly from the USA using ReactiveMicro https://www.reactivemicro.com/product-category/lukazis-loot/ and from Australia using my "Lukazi's Loot" https://lukazisloot.blogspot.com/ website.


Future work.

I'm working with Nick to include 4Play/SNES MAX support into the AppleWin emulator. This will save me a lot of time when it comes to adding software support for these hardware projects. It will also help games such as the PETSCII Robots be more playable in the emulator.

The Bluetooth version of the 4Play card is in development (using an ESP32 chip solution so hopefully WiFi can be added in as there well). Maybe this can even be worked into a Game Port equivalent version at a later stage. The only reason that I'm mentioning this here is because I know that some people have expressed interest in getting the 4Play card at the same time as getting their SNES MAX. Not that the 4Play card will be discontinued but if you are a wireless junkie then you may wish to wait for the new card.


Thank-you.

I just want to thank all the people involved in the "Attack of the PETSCII Robots" project. Thank-you Ian for approaching me for the build and collaborating on the project. Thank-you to Kevin, Dean and Michael for your expert opinions on some of the technical details and making sure I was heading in the right direction. Thank-you to Daniel for keeping me on my toes and making sure I had double checked all the design decisions. Thank-you to the many people who helped with marketing and distribution of the product. Lastly thank-you to everyone else for your support and I wish you many years of enjoyable gaming.



Order your copy of "Attack of the PETSCII Robots" from here http://www.the8bitguy.com/26654/petscii-robots-for-apple-ii-now-available/


Update: 17th July, 2021.

Thanks to Nick's great disassembly notes, the conversion of Robotron 2084 to use the SNES MAX, was much easier than what I was expecting. The game can be found along side other goodies in the attached file below.
SNES MAX example code, schematics, etc https://docs.google.com/open?id=1QYYS0s5PkIrQ3G0R3xiGGfYnjJvZ-FFe


Update: 20th August, 2021.

The SNES MAX is now avialable from ReActiveMicro and Lukazi's Loot.

The 4Play and SNES MAX cards have been emulated in AppleWin. However, currently the configuration is limited and most things are still hard coded. Tom is helping out in getting the user interface part enhanced and getting the code integrated into the live AppleWin release.

I have tested an NES controller (NES-004) with the SNES MAX and it works well. Since the NES controller contains fewer buttons it can only be used with games like Mario Bros where fewer buttons are required. It's like having a SNES controller but where the upper protocol buttons (A, X, Front Left and Front Right) are contstantly pressed down. I'm not going to keep the cables for these in stock but I can make these up as a special order.


Friday, October 16, 2020

Total 4play - Leveraging Total Replay's amazing infrastructure


 
 
Total 4play is a hard drive based collection of arcade style games which have been modified to support digital joystick gameplay, specifically via the 4play card. This compilation has only been made possible due to an amazing bit of infrastructure, called Total Replay, which is what Total 4play is based upon.

Total Replay can be described as a menu selection system and compilation of Apple II games. Compilation sets of Apple II games have been done before but nothing comes close to having the features of Total Replay. To obtain valuable disk space other game compilations have, in the past, resorted to removing parts of the game such as the title screen to cram games together. In contrast, Total Replay aims to preserve all the original content. It uses relatively modern compression techniques and relentless byte saving optimisations to make up for the extra disk storage space needed. The software contains game help pages, original title pages, game demos, an intelligent game title text search engine, original box art where possible, a configurable cheat mode, Control-Reset feature that gets you back to the main menu, a quick loader and bug/compatibility fixes for certain storage media, memory and sound cards. These are just a few of its amazing features. In many ways this software is more than just a game compilation, it's a way to immerse one's self in retro gaming nostalgia but without all the annoyances of the era, such as compatibility issues and relatively slow loading times.

Version 1.0 of Total 4play has be released with twenty converted games. The majority of these games have already been converted to support the 4play. However, these conversions have been done on floppy disk images. There are several advantages to using the Total Replay infrastructure instead of using disk images. These advantages include :-

1. Better grouping of games in one easy usable format. Faster loading and switching between games. Seeing title screens and demos before starting the games.

2. Being able to use any slot of the Apple II for the 4play card. This was more difficult to achieve with individual floppy disk conversions.

3. Having information in the help page that describes which input format (keyboard, Apple II Joystick, Joyport or Gizmo) has been overwritten. Saving the need to look this information up from another source.

4. The second stage of the conversion process (the storage of the changes) is much simpler. In Total 4play this involves applying the changes to the game during the start up sequence where as with the individual floppy disk conversion this meant finding the right places on the disk to modify the code. Having code go across sectors or code that was duplicated multiple times on the disk or code that was compressed made the conversion difficult to perform.

You would have thought that after twenty or so conversions that the conversion process would get simpler due to reoccurring code. However, this has not been the case so far. Apart from the games that were sequels, the code has been different in every one of my conversions. It amazes me how many different ways something can be written in assembly language that performs the same function.

This project will be ongoing. The first round was to work out the infrastructure and get some experience in putting together the games where "stage one" of the conversion process had already been done. Therefore, these first twenty games might not be the best examples of where digital joystick gameplay shines. I missed including some games like "Boulder Dash II", "SuperPuckman" and "Super Taxman 2" because these games were not included in the Total Replay list. The next round of conversions is to work out how to include these into the infrastructure then work on games which make the most sense and the ones which I can still play with for hours on end ie "Snakebyte", "Mr Do.", "Hard Hat Mack", "Pooyan" etc.

Digital gameplay is not not for everyone. It does take away from that nostalgic Apple II experience but does bring that arcade experience closer to the home computer environment. Some people prefer playing games using game controllers over joysticks but my preference is for the arcade joystick, which in my opinion, adds another layer to the experience. For now my original Apple II joysticks have been put away and I'm happy to let other users play with the digital ones. These are much easier to replace.

A big thanks to everyone who made Total Replay possible and for your help in getting me started on my variant. I suspect that Total 4play is not going to be the last offshoot of this wonderful bit of infrastructure. It has the potential to transform many other gaming genres. Think "Total Adventure" or "Total Education". 

Total Replay: https://archive.org/details/TotalReplay

Development: https://github.com/a2-4am/4cade

Total 4play V1.0 (20 games): https://docs.google.com/open?id=17d16hsBl24g0zSSJQ15__4MLEvlPxneH

Development: https://docs.google.com/open?id=1p8x6HZQIU3Pl4gZ3UxQAX3_8uDRLZq_7

Sunday, August 23, 2020

Modern Monitor Solutions - Display Lag


Early home computers were built around the concept of using televisions for a source of display. As monitors became more affordable, monochrome and then colour monitors became the norm. These solutions rely on CRT technology but as time goes on it becomes harder and harder to support, in terms of replacement or in terms of repair. Numerous creative solutions have been designed and built to cater for an ever-increasing demand of CRT screen replacements. A lot of these conversions have focused on getting an image that is as close as possible to the CRT looking display. However, is this being done at the expense of other factors such as the display lag? Do you find it difficult to match that high score you got as a teenager on your favourite game? If so, then maybe it's not due to old age. It may be due to your monitor solution. I compared the display lag on several of today's solutions and I found mixed results.

For those enthusiasts using retro computers for word processing, programming, communications and hardware hacking, the display lag will hardly matter but for the retro gamer it’s an important factor to consider. Everyone will have a different perspective on how authentic they wish their retro experience to be. To some, having to replace their CRT display with an LCD solution would seem unthinkable while to others playing a game on an emulator is nostalgic enough. It will all depend on your time, resources, budget and your level of the "Obsessive Compulsive Disorder". Which is more authentic, playing on a cycle accurate emulator or a physical computer with a modern-day monitor? This is what I wanted to find out.


Frame strip showing a three frame (60ms) delay.

It's generally considered that a lag of 30ms on a display is not going to be noticeable. When you consider one screen refresh will take 20ms when displaying at 50Hz or 16.67ms when displaying at 60Hz then you hope your monitor is not going to have a lag of more than a frame or two. Even 30ms sounds quite a long time to me, considering today's LCD gaming monitors tend to advertise lag to be under 15ms. If you are sitting in front of a computer with just one monitor, then you're probably not going to notice any lag. I first noticed it when developing the A2 Video Streamer which sends video signals over USB to display on a modern-day computer. I wasn't surprised to find that sending video data over a USB feed was going to cause a delay but what I do find surprising is seeing large delays in some modern-day monitor solutions, especially on those that I assumed to have no buffering. Every monitor is going to have lag. Even a CRT monitor. However, the lag on a CRT monitor is going to be in the nanosecond range. For now, I just wanted to test the display lag using tools I had at my disposal. What I wanted to do was to compare a CRT monitor with other video solutions to see how much difference there was. I figured I could do this with a bit of programming and a device to record the video of two monitors side by side.

I started off by writing a simple program that displays a two-digit number at the start of each text line. The number is updated by one and rewritten to the buffer page every time a vertical blank happens. That way the number represents each display frame. Vertical blanking is a pain to write on the Apple II because it is done differently for each of these groups of models 1.Apple II/II+, 2.Apple IIe, 3.Apple IIc/IIc+, 4.Apple IIGS. Since the II/II+ code either requires a hardware modification, extra hardware or substantial amount of programming (specifically lookup tables), I left the code supported only by the computers I had on hand. That is all but the II/II+. Once the program was written, tested and running, all I had to do was to setup each of my computers (IIc, IIe and IIGS) with two monitors at a time and video the results. To do this I used an iPhone and two apps, ProMovie and MoviePro. These apps allowed me to use a predefined frame rate (~50fps and ~200fps for 50Hz). The iPhone seemed like a reasonable option for the accuracy that I was after.



The selected recording frame rate, using the iPhone, was not exact nor was it an exact match to the Apple II's output frame rate, but this did not turn out to be an issue. When looking at the video frame by frame, it allows you to see a scan line coming down the page very slowly. The scan line differences from both monitors can then be compared. Watching the recording of a CRT monitor shows the frame numbers changing over the scan line. However, the recordings of the LCD monitors are not as clear. The change is more gradual, and I suspect this is because filtering is being done to merge the video frames. This makes the comparison process more difficult.


Due to the slight difference in scanning rates between the IIGS and the Video Overlay Card (VOC) we get to see some interesting line updates.

The results are as follows. I will update this list as more test data becomes available.


Model Video 1 Video 2 Lag (Frames)
IIe Composite -> IIc Monitor (Composite) AIIE 80COL64K MEMORY EXPANSION AND VIDEO -> Sony PVM-9045QM Monitor (Composite) 0
IIe Composite -> IIc Monitor (Composite) AIIE 80COL64K MEMORY EXPANSION AND VIDEO -> Sony Portable CD/DVD Player DVP-FX720 (Composite) 0.5
IIe Composite -> IIc Monitor (Composite) AIIE 80COL64K MEMORY EXPANSION AND VIDEO -> Dell U2410 Monitor (Composite) 3
IIc Composite -> IIc Monitor (Composite) Apple IIc Video Expansion -> PAL Modulator Adapter -> Sony PVM-9045QM Monitor (Composite) 0
IIc Composite -> IIc Monitor (Composite) Apple IIc Video Expansion -> BeagleBoneBlackHDMI -> Dell U2410 Monitor (HDMI) 2
IIc Composite -> IIc Monitor (Composite) Apple IIc Video Expansion -> A2 Video Streamer -> PC Laptop Inbuilt Monitor (USB) 2.5
IIGS Composite -> IIc Monitor (Composite) Video Overlay Card -> Sony PVM-9045QM Monitor (RGB) -0.5 to 0
IIGS Composite -> IIc Monitor (Composite) Video Overlay Card -> Sony PVM-9045QM Monitor (Composite) -0.5 to 0
IIGS Composite -> IIc Monitor (Composite) IIGS RGB -> IIGS Monitor (Analog RGB) 0
IIGS Composite -> IIc Monitor (Composite) VidHD -> DELL P2719H Monitor (HDMI) 1
IIGS Composite -> IIc Monitor (Composite) VidHD -> HP P242va Monitor (HDMI) 1
IIGS Composite -> IIc Monitor (Composite) IIGS RGB -> GBS-8200 -> Samsung SyncMaster 740N (VGA) 1
IIGS Composite -> IIc Monitor (Composite) VidHD -> DELL 2407WFPb Monitor (HDMI) 1.5
IIGS Composite -> IIc Monitor (Composite) VidHD -> Dell U2410 Monitor (HDMI) 1.5
IIGS Composite -> IIc Monitor (Composite) IIGS RGB -> GBS-8200 -> Dell U2410 Monitor (VGA) 2.5
IIGS Composite -> IIc Monitor (Composite) IIGS RGB -> GBS-8200 -> VGA to HDMI transcoder -> Dell U2410 Monitor (HDMI) 2.5
IIGS Composite -> IIc Monitor (Composite) IIGS RGB -> Dell U2410 Monitor (Component) 3

The frame counter disk image can be found here. https://drive.google.com/file/d/1pBeuZPA2ChLt88uoHg_weAUq-XgZ0STB/view

Friday, August 14, 2020

Game Controller - H.A.L. Labs Gizmo - Cloning the Cloner


In 1981 H.A.L. Labs released Taxman, a direct Pac-Man clone on the Apple II. Atari was not happy since they held the rights to Pac-Man so they asked H.A.L. Labs to stop selling the software. Atari took Taxman, changed the title and then went on to release the game as their own official Pac-Man for the Apple II platform. Not to be outdone, Taxman's developers re-created the game but this time they made sure that there were enough differences to keep it away from Atari's clutches. It was called Super Taxman 2 and in terms of game play, it was a big improvement. The ghost characters no longer looked like ghosts. The maze layouts were different. However, the running speed and the ghost artificial intelligence made it feel more like a real Pac-Man game.

In their pursuit of performance, the developers became frustrated with the slow speed of the Apple II's analog joystick. In response they created their own joystick solution. They built the Gizmo, which is an adaptor that allows you to use digital joysticks on the Apple II so long as the software is coded to detect the special hardware. In Super Taxman 2 there is no support to play using the Apple II Joystick. It's either the keyboard or the Gizmo. Some levels are so fast it's barely controllable. Try level 88 and you'll wonder if you are playing on a standard Apple II or if you're running via an accelerator.

It was the Gizmo adaptor which interested me the most. This adaptor allows a single digital joystick to be connected to the Apple II and be able to control specific software titles. I could only find two titles which have been adapted to use the Gizmo, Super Taxman 2 and Vindicator (a Robotron clone) also released by H.A.L. Labs. I was unable to locate any information on the construction of the Gizmo so I headed in the only direction I had available to me and that was to reverse engineer the hardware from the software. My investigation led me to conclude that the Gizmo works in a similar way to the Atari Joyport (http://lukazi.blogspot.com/2009/04/game-controller-atari-joysticks.html) which is also an adaptor that allows digital joysticks to be used with the Apple II. However instead of multiplexing the Apple II game port's annunciator output onto three of the push button lines the Gizmo multiplexes the game port's three annunciator outputs onto a single push button line.





To test my assumptions, I put together a board and luckily it worked first go. Here is the schematic for the Gizmo and the truth table used by the software. I'm sure that H.A.L. Labs being in the business of cloning (not all their software titles mind you) are not going to pursue me for recreating their hardware. If the hardware had taken off then doing this back in the day may have been a different story.

If you fancy getting that high speed digital joystick experience without having to go through the pain of creating an adaptor for just two software titles then you will find that I have modified the games to work with the 4play card (http://lukazi.blogspot.com/2017/08/apple-ii-4play-joystick-card-software.html). Since the Gizmo only supports one trigger button it's a pain to play the game Vindicator. This game contains two fire actions (one for shooting and one for the screen bomb). Having to use the keyboard to access the screen bomb annoyed me greatly so in the 4play conversion the screen bomb is mapped to the second trigger button. This makes playing the game much more enjoyable.