nRF52 timer has no modulus?

Question

I'm learning about the nRF52 series and so far love everything I see, especially the SDK. But I just got to the point where I'd like to generate precisely timed output, and there is something I don't understand: the nRF52832 timer seems to have no modulus (wraparound) setting. From what I understand, you can set the prescaler and the bit width, but the timer will still run over the full range of values allowed by the bit width. 
 This seems to imply that you can't produce arbitrary PWM output, only a specific set of PWM periods is supported. 
 Am I missing something?

ovrebekk · Accepted Answer

Hi Jan 
 What you are probably missing is the SHORTS register, which allows you to enable a shortcut between any of the compare events and the clear task. With this enabled you can assign one of the CC registers to act as a reload register, and have the timer reset every time the value in the CC register is reached. 
 Codewise it would look something like this: 
 NRF_TIMER0->CC[3] = 1000; 
NRF_TIMER0->SHORTS = TIMER_SHORTS_COMPARE3_CLEAR_Msk; 
NRF_TIMER0->TASKS_START = 1;
 
 As a side note, if what you need is PWM I would recommend using the dedicated PWM modules. They can also be configured with an arbitrary reload value, in the range 2-(2^15), and allow you to update the duty cycle directly from a RAM buffer without requiring MCU interaction. 
 Best regards 
Torbjørn

nRF52 timer has no modulus?

Top Replies