Post by feijai on Dec 31, 2023 9:51:22 GMT
The title is just an estimate, don't take it as precise.
Mozzi claims that its PWM range on AVR is 0-487. But I have been doing experiments controlling pitch CV with a GRAINS, and have found:
- that 0 (minimum) sent to Mozzi results in a non-zero PWM, maybe about 2 semitones above 0V. You can't go below that.
- that above about 400, Mozzi's PWM starts going quite nonlinear: you can eek out one more semitone, but at a very high value
What it means is that the more or less linear portion of the AVR PWM appears to about 0-400, that is, -244 to +156. I have posted these results to Mozzi's issues list, but I think there is a possibility that they may be specific to GRAINS. I'm hoping someone might have an idea as to whether this limitation is due to output circuitry on the GRAINS, such as its filter or an Op-Amp?
The table below was developed to provide AVR PWM values per semitone. As you can see, there are only 42 of them, not 60.
uint16_t positions[42] =
{
0, 13, 23, 32, 41, 50, 59, 68, 78, 87, 96, 106, // by 9.3, except the first which jumps by 13
116, 125, 135, 144, 154, 163, 173, 182, 192, 202, 212, 222, // by 9.666
232, 242, 251, 261, 271, 281, 291, 300, 310, 320, 330, 339, // by 9.75
349, 358, 368, 377, 386, 397 // by 9.25, except the last which jumps by 11. There's one more pitch but it is highly nonlinear
};
