Explanation of pwm example code please

[nordicdev]

Hi, I need to configure pwm with 14uSec off time and 46uSec on time. I had a look at the pwm example in the install directory and also : developer.nordicsemi.com/.../a00039.html. But it is bit confusing, in the sense, if I need to set a duty cycle of 25% which registers to change. When I change the duty_cycle to 250, or, 100(in the local variable "duty_cycle"), there is no effect in the PWM wave generated. The On and Off times are 256msec always. Even tried pressing the configured buttons, but still no change in duty cycle. Attached my code here: main.c

Questions:

1. Which register to change to set a desired duty cycle(say 25% off time and 75% on time)
2. If I want to use the same PWM module for generating 25% duty cycle outputting on PIN1 for the first time, then 100% duty cycle outputting on PIN2 the next time and the above continues forever, do I need to deinit the gpiote and configure(nrf_gpio_tsk_config) every time I swap the PWM pins?

[Ole Bauck]

You are using code from SDK 8, which is old (the newest SDK is version 11). Now there is a PWM library which is more documented and does not have problems like possibility of inverting the output signal as the earlier SDK examples had. Take a look at the PWM example in SDK 11. You should not use PWM library/example code prior to SDK 10.

[nordicdev]

I have got thist ot work by just copy pasting the code that I have sent you into another working project. Now, how do I set the number of cycles for the PWM? I need just 3 cycles of PWM(on time: 34usec, off time:14usec) after those 3 cycles, I need 10msec delay, then 3 cycles of PWM and the sequence continues. I tried using a different timer to keep track of the number of cycles, but does not work very well. Ideas please..

[Ole Bauck]

Again, if you are using SoftDevice I will strongly not recommend to use this code to generate PWM.

To solve your problem you can add a counter in TIMER2_IRQHandler(). Increment the counter every time the handler is called. If the counter reach 3, then turn off the PPI channels and clear the counter. After 10ms turn on the PPI channels again and clear the timer.

[nordicdev]

Thanks Ole. It works. But, I need softdevice + PWM to work. This is because I need BLE and control the duty cycle of the PWM pulses from the bonded BLE mode from the mobile phone App. As I need PWM pulses of on time 42usec and off time 14usec, this would be disturbed if softdevice is used, because softdevice has higher IRQ priority than timer. How to handle this situation? Thanks

[Ole Bauck]

I am a bit confused here, what exactly did you need to control? You say that the PWM should have pulses of 42 usec (or 34usec in an earlier comment) and off time of 14 usec and at the same time you say that you should be able to control the duty cycle.