Sources for 8b TTL keyboards (Keytronics)

Gordon JC Pearce MM3YEQ gordonjcp at
Sun Dec 7 17:26:04 CST 2008

Tony Duell wrote:
>> On 6 Dec 2008 at 14:33, Kevin Schoedel wrote:
>>> I don't know PIC, but for the AVR equivalent the host requirements are an
>>> RS-232 port and the ability to run gdb.
>> Later PICs have on-chip breakpoint debug communication via ICD (a 3-
>> wire interface)--and there is the ability to run ICE4000.
>> There is at least one AVR open-source debug package that operates 
>> through the SPI programming interface--using the same tool to program 
>> and debug.  
> Can you program and debug either or both of these chips without 
> propietary hardware or software. In other words, is documentation for the 
> following availalbe (without signing an NDA, etc )
> 1) How to send/receive words to the chip (what lines to wiggle and how, 
> what voltages to apply, etc)
> 2) The binary instruction set 
> 3) THe debugging commands/responses

AVR will quite happily send you several kilos of dead trees detailing 
all this and more, if you ask them.  I find that since I'm generally 
carrying several kilos of laptop already, the PDF editions will suffice.

> Could I, if I wanted, make the programmer and write the software from 
> scratch?

Since avr-gcc and avrdude are already available under the GPL and fully 
documented, there's no real need to reinvent that particular wheel.

In short - if you wanted to program an AVR the "oldskool EPROM" way by 
setting lines by hand and toggling VPP with a push switch, you could 
(and I have seen this done!).  It may be slightly more worth your time 
and effort to learn how to use the existing tools ;-)


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