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Subject: |
Re: [avrdude-dev] How to add I2C device disable preamble? |
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Date: |
Tue, 10 Apr 2007 21:52:41 -0700 |
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Thunderbird 1.5 (X11/20051201) |
Bob Paddock wrote:
There is no
program to run yet, you can't program
the I2C disable bit. :-<
OK, that *is* bone-headed.
After reading the whole thread, the best idea that comes to mind is to
build a small fixture that is a repeater board between the production
programmer and the product. The germ of the idea is that the repeater
board should disable the I2C part, and then become transparent to the
ISP programmer.
Possible implementation:
1) ISP headers in and out for connection to programmer and product.
These are wired through, or may need buffers.
2) A small AVR, wired to bit-bang the SPI lines.
3) Software that:
a) bit-bangs the magic "I2C-B-Gone" sequence onto the
outing SPI header. (Hard coded, or stored in eeprom,
or whatever)
b) tri-states the AVR so that the ISP can drive
I suppose it may also require some buffers or so forth so that the
bit-bang sequence doesn't back-drive the AVR-ISP or something, but
perhaps some or all of the lines can simply be wired through.
And, it will become a production line problem unless a very simple
software interface can be designed to drive the whole programming rig in
the right sequence from a script. So, maybe the fixture board needs to
have an RS-232 serial interface on it so that it can triggered from a
script.
-dave
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