Software PWM

[keyeh]

I'm working on a project that requires some more PWM capable pins.

I'm going to try software PWM over shift registers. I'll submit a PR if I can get it to work.

Maybe with an API like this, where dutyCycle is 0-255. Same as analogWrite on Arduino.

void writeBit(int bitnum, uint8_t dutyCycle);

[newmedio]

Sounds like it would be really slow, but I'll accept a patch. You might try to do it using my Eventually library.

[newmedio]

In fact, the easier method might be to write a "cycle" method for Eventually.

[keyeh]

Did some basic experiments at around 440 Hz on atmega328 using shiftOut(). For reference the hardware PWM is about 490 Hz.

At 440 Hz the minimum duty cycle is about 20% and max is 80%. Could get more range by lowering the frequency.

I'll try this with an ESP8266, which can run at 160 MHz vs 16 MHz on the arduino. Could definitely get more duty cycle range even at higher freq. like 1 KHz.

The better way to do it would be to use SPI