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Originally Posted by Kyveck
Our robot's motors seem to be receiving some sort of signal even when all pwm outs are hardcoded to zero. We systematically turned off sensors and bits of code, until we isolated the problem with the adc software. Unless we disable the adc code, (by commenting out the adc initialization or the adc/timer interrupt routines) the drive wheels act as if they are set to 10 or 20 above neutral, instead of 127. If we enable the joystick and pull it back about 10 or so, the wheels stop. If we set one wheel to be mapped as (255-p2_y) then ten forward or so stops one wheel and speeds up the other, and vice versa. If we change the sampling rate from 200Hz that we were using to 800Hz, then the wheels spin much faster, but in the same manner.
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This explains the symptoms we've been seeing as well. Our current code (which uses Kevin's ADC code for the gyro, DAA, and one other channel) shows a slightly positive value on the PWMs, but the default code doesn't. It 's not causing us any problems, but it's enough to cause the CIMs to hum even when everything is set to 127.