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/diy/ - Do It Yourself

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>> No.1769479 [View]
File: 2.21 MB, 3264x7200, MISO waveforms.jpg [View same] [iqdb] [saucenao] [google]
1769479

>>1768810
>>1768824
Just updated the firmware, no dice.
But with the scope out I'm getting a proper waveform on MOSI but the signal on MISO is only 0.5V high with a bit of a capacitive ramp on it centred around 0V. I tried slapping a pullup on MISO in place of the slave ATmega, and it wasn't pulled to ground by the programmer or anything. When I detach the MISO line I get the same low-amplitude signal on the arduino's MISO pin. The MISO wave seemed to be rather affected by ambient noise (there is a 20mV mains-freq wave sitting on top of it) so I added a 100k pulldown resistor but only the edges of the MISO wave remained; the rest gets pulled to ground and I'm left with a very spiky waveform. I'm convinced that the path from the slave MCU to the MISO pin goes through a high-pass filter, it's the only thing that makes sense. But it also gets attenuated far too much for the programmer to read.

Also the apparent frequency of the data on both MOSI and MISO seems to be rather high at the start of the attempted fingerprinting before settling to a much lower frequency/bitrate. Pic related is with -b set to 300 with the scope paused as soon as I could. I'm having a hard time getting my single triggering to function, probably because of the noise.

I'm going to test my diy ATmega dev board next.

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