Hello,
I'm looking to be able to adjust PWM output frequency around 100KHz in 100Hz (or close to it) steps. I understand that no matter which method you use the implement PWM, the limitation is the max clock rate of 16Mhz. I've tried this with app_pwm, the pwm driver, and writing my own pwm driver using GPIOTE+PPI/TIMER and have run into this limitation with each method (which makes sense). At a simple level, if I want a 50% duty cycle PWM and am using a 16MHz counter...
- A compare at 1 clock cycle = 8Mhz freq
- A compare at 2 clock cycles = 4Mhz freq
- A compare at 3 clock cycles = 2.66Mhz freq
- A compare at 4 clock cycles = 2Mhz freq
- ...
- A compare at 76 clock cycles = 105263.16 Hz
- A compare at 77 clock cycles = 103896.10 Hz
- A compare at 78 clock cycles = 102564.10 Hz
- A compare at 79 clock cycles = 101265.82 Hz
- A compare at 80 clock cycles = 100000.00 Hz
- A compare at 81 clock cycles = 98765.43 Hz
- A compare at 82 clock cycles = 97560.98 Hz
- etc
What I would really like is to be able to adjust the frequency between 90Khz and 110Khz in 100Hz steps.
Is there some clever way to get better frequency resolution around 100Khz, or am I going to need some external hardware to achieve this?
