PWM on 3 pins

[bojerko]

I have a nrf51 dongle and would like to use PWM on 3 pins. Managed to get it working on pins 15 and 16, but somehow pins from 17 to 20 just don't work. For example: I set an LED on pin 17 and when using PWM it turns on and immediately off.

To use PWM on three pins I resorted to using 2 timers (TIMER1 and TIMER2) and the code is like that:

app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_2CH(5000L, 15, 16);
err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
APP_ERROR_CHECK(err_code);
app_pwm_enable(&PWM1);
ready_flag = false;
while (app_pwm_channel_duty_set(&PWM1, 0, 0) == NRF_ERROR_BUSY);
while(!ready_flag);
APP_ERROR_CHECK(app_pwm_channel_duty_set(&PWM1, 1, 0));

app_pwm_config_t pwm3_cfg = APP_PWM_DEFAULT_CONFIG_1CH(5000L, 17);    
err_code = app_pwm_init(&PWM1,&pwm3_cfg,pwm_ready_callback3);
APP_ERROR_CHECK(err_code);
app_pwm_enable(&PWM2);
ready_flag3 = false;
while (app_pwm_channel_duty_set(&PWM2, 0, 50) == NRF_ERROR_BUSY);

If I try setting the pin 17 with command nrf_gpio_set(17) LED turns on without a problem. I have even tried using only 1st part of the code (just 2 channels), but if I use any pin from 17 on the PWM doesn't work.

BTW - I'm using SDK11.

Any ideas, what I might check?

[Sigurd]

Hi,

It looks like you are initializing the first PWM instance twice. I.e. you should change your line

err_code = app_pwm_init(&PWM1,&pwm3_cfg,pwm_ready_callback3);

to

err_code = app_pwm_init(&PWM2,&pwm3_cfg,pwm_ready_callback3);

[bojerko]

Ah, yes. I missed this one. Thanks for that. At least 15 and 16 are now on, but 17 is still off :/

[Sigurd]

Are you using TIMER2 for the PWM2 instance? i.e.:

APP_PWM_INSTANCE(PWM2,2);

[bojerko]

I just copied APP_PWM_INSTANCE(PWM1,1); and changed PWM1 to PWM2. Now I change the 1 to 2, but get the error: error: 'TIMER2_INSTANCE_INDEX' undeclared here (not in a function)

I guess I need to setup something in nrf_drv_config.h although both timers are on (1 and 2). Do you have an idea what might be solution to that? Thanks.

[Sigurd]

Yes, you need to make sure that you have #define TIMER2_ENABLED 1 in nrf_drv_config.h

[bojerko]

Ah yes ... for some strange reasons I have two nrf_drv_config.h files and in one the setup was proper, but in the other not. So it compiles, but the LED on the pin with PWM2 still doesn't light on. If I move it to PWM1 it turns on. Looks like I'm still missing something in setting :(