Tuesday, July 1, 2008

External CF

The programming of the microcontroller is going to take a while. I will try and update my progress as much as possible but in the mean time I'll leave you with posts on some of my smaller projects.

External Compact Flash (CF) - External enclosure for IDE/ATA controller.

To add software to my Compact Flash (CF) based hard drive (MicroDrive IDE controller supplied by ReactiveMicro.com) I was constantly opening the case to get to the card. The idea was to extend the IDE/ATA connection and get the CF card external to the IIGS. I was unable to use a standard IDE/ATA cable because it contained female plugs and so did the CF adapter that came with the IDE controller. Tracking down a straight through 40 pin extension cable (male one end and female on the other) proved to be unsuccessful.

I ended up purchasing a CF adapter with a 40 pin female connection (39 pins actually), hooked it up and to my surprise nothing happened. At first I could not get it to work at all. Power needed to be supplied to the CF adapter's power connector. It was missing pin 20 (KEY pin) which the original CF adapter used as an alternate 5 volt power source. I set about modifying the IDE controller card by adding two pins for external power however I never ended up using it because of a change in plan. Using the new CF adapter was going to be an ugly solution. Not only was the cable short but the power cable would have to be run alongside it. The power could have been fed via pin 20 of the IDE/ATA cable but that would have meant modifying the equipment (IDE/ATA cable, CF adapter) or creating new adapters.

Instead I chose to use the original CF adapter and managed to get a custom cable made up (Supplied by Qld Connectors & Cables - http://www.qconnect.com.au/). This also meant I could have a longer cable. The IDE/ATA bus is specified to be used up to a maximum length of 46cm. However, cables up to about 90cm have been used successfully. I picked a length of 70cm which would allow the CF adapter to sit nicely at the side of the IIGS. To run the cable through the IIGS slot I sliced the cable in three so that it would fit in without bending. The slot is quite sharp so it was a delicate job feeding it through. Finally I purchased a plastic enclosure from a local electronics store and my father helped me mount the adapter inside. Two light transporters were used to move the power and read/write signals to the front panel. A fair bit of the light is lost this way. From my sitting position I can see the power light even though it is dull but to make out the read/write light I need to move so that my eyes are in line with it. Rewiring the LEDs would have been a better performing option.

I was concerned with not having external power on the CF adapter but so far I have not had any problems. Then again my IIGS power supply isn't overloaded.

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