nRF52: "spike" after last period with inverted polarity PWM

RE: nRF52: "spike" after last period with inverted polarity PWM

Magneon — Mon, 28 Mar 2022 18:10:59 GMT

I still think this might be a bug, but in my case I was able to work around this by sticking a full "0" at the end (1<<15 in this case to set the inverted flag on a 0 output), and increasing my buffer size by 1.

Before I was seeing this weird tiny spike at the end, and after it was gone.

Obviously this won't work in all cases, but should work in most.

RE: nRF52: "spike" after last period with inverted polarity PWM

haakonsh — Fri, 26 Jul 2019 09:30:01 GMT

Hey Franz, I'm so sorry for the long delay.

I've tried to reproduce your issue on an internal test board, but I cannot produce the same spike.

I suggest you turn on high drive on the gpio via the GPIO HAL, or use:

NRF_GPIO->PIN_CNF[31] |= (3 << 8); // High drive '0', high 'drive '1'

Source for this issue is interference, loading of the PWM trace, poor grounding, etc.

RE: nRF52: "spike" after last period with inverted polarity PWM

Franz — Tue, 04 Jun 2019 06:02:22 GMT

Hi haakonsh - any news on that?

RE: nRF52: "spike" after last period with inverted polarity PWM

Franz — Wed, 29 May 2019 12:28:27 GMT

I could, but would need to remove some confidential stuff before, I guess.

However, here is the PWM related passage of sdk_config.h (the legacy layer PWM stuff is commented out")

// <e> NRFX_PWM_ENABLED - nrfx_pwm - PWM peripheral driver
//==========================================================
#ifndef NRFX_PWM_ENABLED
#define NRFX_PWM_ENABLED 1
#endif
// <q> NRFX_PWM0_ENABLED  - Enable PWM0 instance
 

#ifndef NRFX_PWM0_ENABLED
#define NRFX_PWM0_ENABLED 1
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_OUT0_PIN - Out0 pin  <0-31> 


#ifndef NRFX_PWM_DEFAULT_CONFIG_OUT0_PIN
#define NRFX_PWM_DEFAULT_CONFIG_OUT0_PIN 31
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_OUT1_PIN - Out1 pin  <0-31> 


#ifndef NRFX_PWM_DEFAULT_CONFIG_OUT1_PIN
#define NRFX_PWM_DEFAULT_CONFIG_OUT1_PIN 31
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_OUT2_PIN - Out2 pin  <0-31> 


#ifndef NRFX_PWM_DEFAULT_CONFIG_OUT2_PIN
#define NRFX_PWM_DEFAULT_CONFIG_OUT2_PIN 31
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_OUT3_PIN - Out3 pin  <0-31> 


#ifndef NRFX_PWM_DEFAULT_CONFIG_OUT3_PIN
#define NRFX_PWM_DEFAULT_CONFIG_OUT3_PIN 31
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_BASE_CLOCK  - Base clock
 
// <0=> 16 MHz 
// <1=> 8 MHz 
// <2=> 4 MHz 
// <3=> 2 MHz 
// <4=> 1 MHz 
// <5=> 500 kHz 
// <6=> 250 kHz 
// <7=> 125 kHz 

#ifndef NRFX_PWM_DEFAULT_CONFIG_BASE_CLOCK
#define NRFX_PWM_DEFAULT_CONFIG_BASE_CLOCK 4
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_COUNT_MODE  - Count mode
 
// <0=> Up 
// <1=> Up and Down 

#ifndef NRFX_PWM_DEFAULT_CONFIG_COUNT_MODE
#define NRFX_PWM_DEFAULT_CONFIG_COUNT_MODE 0
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_TOP_VALUE - Top value 
#ifndef NRFX_PWM_DEFAULT_CONFIG_TOP_VALUE
#define NRFX_PWM_DEFAULT_CONFIG_TOP_VALUE 1000
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_LOAD_MODE  - Load mode
 
// <0=> Common 
// <1=> Grouped 
// <2=> Individual 
// <3=> Waveform 

#ifndef NRFX_PWM_DEFAULT_CONFIG_LOAD_MODE
#define NRFX_PWM_DEFAULT_CONFIG_LOAD_MODE 0
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_STEP_MODE  - Step mode
 
// <0=> Auto 
// <1=> Triggered 

#ifndef NRFX_PWM_DEFAULT_CONFIG_STEP_MODE
#define NRFX_PWM_DEFAULT_CONFIG_STEP_MODE 0
#endif

// <o> NRFX_PWM_DEFAULT_CONFIG_IRQ_PRIORITY  - Interrupt priority
 
// <0=> 0 (highest) 
// <1=> 1 
// <2=> 2 
// <3=> 3 
// <4=> 4 
// <5=> 5 
// <6=> 6 
// <7=> 7 

#ifndef NRFX_PWM_DEFAULT_CONFIG_IRQ_PRIORITY
#define NRFX_PWM_DEFAULT_CONFIG_IRQ_PRIORITY 6
#endif

// <e> NRFX_PWM_CONFIG_LOG_ENABLED - Enables logging in the module.
//==========================================================
#ifndef NRFX_PWM_CONFIG_LOG_ENABLED
#define NRFX_PWM_CONFIG_LOG_ENABLED 0
#endif
// <o> NRFX_PWM_CONFIG_LOG_LEVEL  - Default Severity level
 
// <0=> Off 
// <1=> Error 
// <2=> Warning 
// <3=> Info 
// <4=> Debug 

#ifndef NRFX_PWM_CONFIG_LOG_LEVEL
#define NRFX_PWM_CONFIG_LOG_LEVEL 3
#endif

// <o> NRFX_PWM_CONFIG_INFO_COLOR  - ANSI escape code prefix.
 
// <0=> Default 
// <1=> Black 
// <2=> Red 
// <3=> Green 
// <4=> Yellow 
// <5=> Blue 
// <6=> Magenta 
// <7=> Cyan 
// <8=> White 

#ifndef NRFX_PWM_CONFIG_INFO_COLOR
#define NRFX_PWM_CONFIG_INFO_COLOR 0
#endif

// <o> NRFX_PWM_CONFIG_DEBUG_COLOR  - ANSI escape code prefix.
 
// <0=> Default 
// <1=> Black 
// <2=> Red 
// <3=> Green 
// <4=> Yellow 
// <5=> Blue 
// <6=> Magenta 
// <7=> Cyan 
// <8=> White 

#ifndef NRFX_PWM_CONFIG_DEBUG_COLOR
#define NRFX_PWM_CONFIG_DEBUG_COLOR 0
#endif

// </e>

// </e>

RE: nRF52: "spike" after last period with inverted polarity PWM

haakonsh — Fri, 24 May 2019 11:28:42 GMT

Yeah, I need the configuration of the PWM peripheral in sdk_config.h.

Do you mind sending me your project?

RE: nRF52: "spike" after last period with inverted polarity PWM

Franz — Tue, 21 May 2019 12:24:56 GMT

Sorry, I missed that:

#define NBR_ADC_SAMPLES_AO 1024

Still something missing you need to know?

RE: nRF52: "spike" after last period with inverted polarity PWM

haakonsh — Tue, 21 May 2019 07:43:00 GMT

I need the value of NBR_ADC_SAMPLES_AO as well. I want to reproduce the issue on my end.

RE: nRF52: "spike" after last period with inverted polarity PWM

Franz — Thu, 16 May 2019 13:32:51 GMT

  nrf_pwm_values_individual_t seq_values[] = {0x8000|64, 0x0000|26}; //15 bit value, 16th bit = polarity
  nrf_pwm_sequence_t const seq =
  {
      .values.p_individual = seq_values,
      .length          = NRF_PWM_VALUES_LENGTH(seq_values),
      .repeats         = 0,
      .end_delay       = 0
  };

Sorry, it´s been some time - here it is!

RE: nRF52: "spike" after last period with inverted polarity PWM

haakonsh — Fri, 26 Apr 2019 09:28:05 GMT

It kinda looks like the sequence is 'off by one'. Can you share your 'seq' struct?

RE: nRF52: "spike" after last period with inverted polarity PWM

Franz — Wed, 24 Apr 2019 05:42:23 GMT

Hi haakonsh,

See the code snippet below.

A falling edge on the HELPER_PIN should start the PWM

 
 
 //configure gpiote
 nrfx_gpiote_in_config_t helper_pin_cfg = NRFX_GPIOTE_CONFIG_IN_SENSE_HITOLO(true);
 err = nrfx_gpiote_in_init(HELPER_PIN, &helper_pin_cfg, NULL);
 nrfx_gpiote_in_event_enable(HELPER_PIN, false);
 
 
 //configure ppi channel
 uint32_t start_task_addr = nrfx_pwm_simple_playback(&m_pwm0, &seq, NBR_ADC_SAMPLES_AO, NRFX_PWM_FLAG_START_VIA_TASK|NRFX_PWM_FLAG_STOP);
 
 nrfx_ppi_channel_alloc(&ppi_ch_start_clk);
 nrfx_ppi_channel_assign(ppi_ch_start_clk, nrfx_gpiote_in_event_addr_get(HELPER_PIN), start_task_addr);
 nrfx_ppi_channel_fork_assign(ppi_ch_start_clk, nrfx_timer_task_address_get(&m_tmr1, NRF_TIMER_TASK_START));
 nrfx_ppi_channel_enable(ppi_ch_start_clk);

RE: nRF52: "spike" after last period with inverted polarity PWM

haakonsh — Tue, 23 Apr 2019 14:33:04 GMT

We need more information on how exactly you've implemented "gpiote_in_event to trigger a number of PWM pulses".

Are the IN_EVENT pin or PWM pin driven high or low?