Re: Homebrew STG card

[stratton-at-mdc.net]

> With regards to the Xilinx FPGA chips, I have access to computers that
> can program them if people want.  I would need a bit of help though.  I
> also have Xilinx on my personal computer, but don't have the hardware.

This borders on tangential, but there are types of FPGA's that use
RAM based configuration cells that must be intitialized after each
power on.  Usually this is done with a little 8-pin serial EEPROM, but
the configuration data can be sent from a computer as well.  So I
think it would ultimately be nifty to have a setup where a minimal PCI
or ISA 'bootstrap' bus interface is loaded from EEPROM at powerup, and
then the computer can downlaod custom configuration code.  If/when
this becomes possible and a GPL verilog compiler is written, then the
servo/encoder interface hardware could more or less become part
of the EMC distribution!

Acutally, a more doable and safer implimentation would be to load the
entire FPGA from EEPROM, but have a register in the FPGA that can be
used to reprogram the EEPROM much like the way you can 'flash' a bios
upgrade.  A certain sequence of bytes might have to be written first
to enable this mode, and physical jumpers could disable it, or
possibly bank-switch to a backup configuration in case of data
corruption.

This is of course somewhat tangential to the goal of getting a cheap
and easy servo interface.  But I'm sure I'm not the only one here with
"Tangential" as a middle name - supposedly I'm making french horns,
but seem to spend more time planning improvements to the machine
tools...

Chris

-- 
Christopher C. Stratton, stratton-at-mdc.net
Instrument Maker, Horn Player & Engineer
30 Griswold Street, Cambridge, MA 02138
http://www.mdc.net/~stratton
(617) 492-3358 home/shop