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Re: [avr-chat] STK500 w/ EEPROM chips


From: Kyle Evans
Subject: Re: [avr-chat] STK500 w/ EEPROM chips
Date: Sun, 09 Aug 2015 16:22:43 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.8.0

On 08/09/2015 12:31 PM, Michael Hennebry wrote:
On Sat, 8 Aug 2015, Kyle Evans wrote:

On 08/07/2015 03:42 PM, Michael Hennebry wrote:
On Fri, 7 Aug 2015, Kyle Evans wrote:

Can avrdude and the STK500 write to a stand-alone EEPROM chip, for
something like flashing coreboot onto a motherboard EEPROM chip.

Probably not.
avrdude and STK500 are for AVRs and use their protocols.
A stand-alone EEPROM will probably not use the same protocol.
That said, if the EEPROM is made  by Atmel, it might use the same
protocol.
One can always check the specs.


By protocol do you mean command set? They both support SPI and ISP.
The data sheet for the chip has all of the commands, but I have not
yet found any related material in any of the documentation that I have
for the STK500. Which, is kind of why I'm fishing to see if anyone has
tried this. My next step is to compile avrdude and see what I find.

More or less.

SPI is just a hardware specification for moving bits around.
It says nothing about how those bits are interpreted.
AVR ISP is SPI with a particular interpretation of the bits.
IIRC it is pretty much uniform for all AVR that accept it.

Quite probably one can do ISP with things that are not Atmel.
Different bit sequences would likely be required.

In the case of a chip mounted on an STK500,
there can be two protocols involved:
PC to STK500 and STK500 to chip (ISP).
AVR Studio understands PC to STK500.
STK500 understands ISP.
Also, the STK500 con be configured so that
ISP can be done directly by external hardware,
some of which can be controlled by avrdude.
IIRC avrdude understands PC to STK500.
avrdude also understands several other programmers.

I think that there are programmers that could be configured to do
what you want and that avrdude could be configured to control them.
Finding them and doing so is left as an exercise for the reader.
Deciding whether that is too much exercise
is also left as an exercise for the reader.

AFAIK the STK500 has no understanding of anything
other than AVR microcontrollers.


I think I have clarity of the situation now, thanks.
I did some more digging in the manual, and found that the "spare" RS-232 port is, potentially, what I could use:

"The other RS-232 can be used for communication between the target AVR microcontroller in the socket and a PC serial port connected to the RS-232."

So, using the main RS-232 port is out of the question because the socket is behind a proprietary interface and the firmware would not recognize the device ID of my chip. However, the "spare" port bypasses this interface and exposes the chip directly to the PC serial port.

AVRdude speaks to this proprietary interface, but also can speak RS-232 and could potentially be taught about my chip, but a better route would be to get it working through flashrom, which already understands the chip and can also speak RS-232.

I'll report back with my findings once I find my RS-232 cable, a spare chip, and have done some testing.

Thanks,
Kyle



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