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Topic: Struggling with bootloader onto TQFP atmegas (Read 4530 times) previous topic - next topic

PolkaDot

I think I figured out the problem.. my board multiplexes the SPI bus to other ICs. I thought just disabling the MUX would be enough, but it seems to be still loading the pins. When I added resistors in series between the ICSP and MUX, as per:
http://www.atmel.com/ja/jp/Images/Atmel-2521-AVR-Hardware-Design-Considerations_Application-Note_AVR042.pdf
the bootloader made it!

Out of curiosity, does anyone know what value R is appropriate here? The appnote doesn't give values, and I used 220R because they were on hand. Will check that the SPI still works as intended tomorrow.

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