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By: sdb (offline) on Thursday, January 26 2012 @ 10:57 PM PST (Read 662 times)  

Built one of two Larson kits and it is working great. (I expect the other will be fine as well.)

I bought it to play around with the ATtiny2313, so I added the 6pin ISP header.

It took some time, but I was (finally) able to reprogram the t2313 with the ISP shield using a modified ArduinoISP on a new Diavolino.

Why "finally" and what "modified" ?

Neither the example project in Arduino 022 nor the latest from the MegaISP code repository worked on the t2313. They seemed to work fine doing "read only" against my other Diavolino.

Symptoms on the t2313: unable to read the signature, unable to read the fuses, unable to sync, etc. All sorts of errors at random times in the process, indicating the communication was not working well.

Cause: Evidently the low clock speed of the t2313 on the ix board is not happy with the built-in SPI clock speed (16MHz Atmega328), even as slow as the SPI CR could be set to go (I think it was already minimum speed, at least I couldn't find any slower bitmask).

Fix: Put in alternative code to bitbang (with digitalWrite()) the SPI data transfer instead of using the built-in SPI support. (A better fix would be any of: automatically slow down if needed, or expose a mechanism that AVRDude could use to select the speed like other programmers, or detect a shunt on the shield to select fast vs slow.)

Test: Was able to read the original code from the t2313 as shipped by EMSL, build the code from source, program the t2313, run it normally, read it back out, and it compares identical to what was read originally.

Test 2: Was able to program the Menorah code. Currently running demo mode in less-bright flicker mode.

Awesome. Smile (but I find the flicker a little bit frantic. might have to fix that!)

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