Homebrew STG card

[Paul Corner <Paul.Corner-at-tesco.net>]

Hi Folks

The story so far...
I've managed to blag a couple of free samples of the MAX547 DAC.So when they
turn up, I'll start playing with the analog circuits.
Located some info on the PCI bus - The overview covered the basics, and it
looks as if it would be a real pain to meet the required specifications. The
bridging logic is what really puts me off going down the PCI route.
The Xilinx chips are appealing, agian I had a look at the overview datasheets.
As I uderstand it, these chips have all the configureation data stored on a
serial EEPROM which is loaded at power on. As the Xilinx devices can not be
partiallly updated, the whole device would have to be reprogramed. With a small
amount of software to 'blow' the EEPROM, there would be no need for fancy
expensive programmers. This technology is worth looking into - not that I would
want to myself, the cost of the tools does not justify it.
If someone else on the list would like to take up the challenge to intergate
much of the digital IO onto one of these devices, I'll offer what support I can.
In the mean time, I was going to use the designs by Tom Kulaga as a starting
point. Map one or two 8255 chips into LPT3, and use 0x300 to 0x31F for the
analog IO. If needed, maybe mapping the LS7266 into the same area.
Connecting to the outside world, I would envisage possibly using 9 pin D
connectors for the encoders pin compatable with the Heidenain scales. Analog IO
on a seperate 26 pin D connector and the digital IO on a 50 way box header.
This way, if anyone wanted to start with just a stepper system with a clear
path to a full blown servo control, all they would need to do is to plug in the
missing chips and hook up the cables.

Comments ?

Regards, Paul