PWM individual decoder not working

[micallef25]

Hi all,

I have two pwm pins I would like to have them run at two different duty cycles. My understanding is that we can do this by setting the decoder to individual. When I set this register to individual my output flat lines. Although, When I set it to grouped both of my PWM pins output a pwm at 60hz 50% duty cycle as expected.

Below is my code.

uint16_t pwm_doody[2]={0x250, 0x421};

NRF_PWM0->PSEL.OUT[0] = (PWM_PINA << PWM_PSEL_OUT_PIN_Pos)|(PWM_PSEL_OUT_CONNECT_Connected << PWM_PSEL_OUT_CONNECT_Pos);

NRF_PWM0->PSEL.OUT[1] = (PWM_PINB << PWM_PSEL_OUT_PIN_Pos)|(PWM_PSEL_OUT_CONNECT_Connected << PWM_PSEL_OUT_CONNECT_Pos);

NRF_PWM0->ENABLE = (PWM_ENABLE_ENABLE_Enabled << PWM_ENABLE_ENABLE_Pos); NRF_PWM0->MODE = (PWM_MODE_UPDOWN_Up);

NRF_PWM0->PRESCALER = (PWM_PRESCALER_PRESCALER_DIV_128);

NRF_PWM0->COUNTERTOP = (0x823);

NRF_PWM0->LOOP = (PWM_LOOP_CNT_Disabled);

NRF_PWM0->DECODER = (PWM_DECODER_LOAD_Individual << PWM_DECODER_LOAD_Pos)|(PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos);

NRF_PWM0->SEQ[0].PTR = ((uint32_t)(pwm_doody) << PWM_SEQ_PTR_PTR_Pos);

NRF_PWM0->SEQ[0].CNT = ((sizeof(pwm_doody) / sizeof(uint16_t)) << PWM_SEQ_CNT_CNT_Pos);

NRF_PWM0->SEQ[0].REFRESH = 0;

NRF_PWM0->SEQ[0].ENDDELAY = 0;

NRF_PWM0->TASKS_SEQSTART[0] = 1;

[Sigurd]

Hi,

For PWM_DECODER_LOAD_Individual, the pwm_sequence table need to be a length of 4.

Change

uint16_t pwm_doody[2]={0x250, 0x421};

to

uint16_t pwm_doody[4]={0x250, 0x421,0,0};

[micallef25]

Ok, follow up comment then, why is that??

[Sigurd]

When configured as Individual, one duty cycle value is required for each compare register. It have to do with how the PWM is fetching the COMPARE values from RAM.

[micallef25]

That makes sense, Thank you for your help (:

[obbe]

Thanks for this! I spent the better part of yesterday trying to figure this out. Is this mentioned in the documentation somewhere? Because I didn't find anything.