Is it possible to make 5 PWM outputs on NRF51422 (or NRF51822)?

[Brandon A]

I know that it is possible to make 4 PWM outputs, but I need to generate 5. I will be using SoftDevice 110 and BLE. Is there any possible way to generate a 5th PWM output?

Any advice would be much appreciated.

[Øyvind Karlsen]

Hi,

We have 4 compare events per timer instance, for each of these 4 one will be used as a reset. That means that we're left with three possible outputs per timer. In operation alongside the SoftDevice we will have access to two timers, this gives us a total of 6 outputs.

The problem is that we only have 4 GPIOTE slots, which means that you will not get reliable PWM output, this might be fine if you want to control a LED or simple motor.

For help on implementation search google for "bit bang pwm", and there should be some useful results.

Best regards,

Øyvind

[Brandon A]

Hi Øyvind,

Thanks for your answer. When you say that I will not be able to get reliable PWM output on a 5th pin, do you mean that bit bang pwm won't give reliable output, or is there a way to send a 5th PWM output to a non-GPIOTE pin that is unreliable?

[Øyvind Karlsen]

Bit bang is not reliable, GPIOTE helps make the big bang implementation more reliable. For the 5th PWM you would not have a GPIOTE available, that makes things even harder.

[Brandon A]

Ok, I see. I don't think I will try to add a 5th pwm output then. Thanks for helping!