Please give me advice on nrf pwm driver.

Question

I want a waveform as below for motor control. I am trying to create this using nrf pwm driver. 
 I set the pwm sequence as below and checked the output. 2nd duty repeat does not work. 
 I added an unused 3rd dummy duty (line 91). It seems to be working well. 
 However, increasing the playback count to 2 introduces a delay between the outputs. 
 What should I do to get the waveform I want? Give me advice . Thanks.

Jared · Accepted Answer

Hi there, Although it's not well explained in the product specification, the PWM peripheral has a limitation in that it will stop the execution of a sequence too early. Some effort has been done to explain it in some part in this thread . Nevertheless, the best way for your use case is to something like this: #include #include #include "nrf_drv_pwm.h" #include "app_util_platform.h" #include "app_error.h" #include "boards.h" #include "bsp.h" #include "app_timer.h" #include "nrf_drv_clock.h" #include "nrf_delay.h" #include "nrf_log.h" #include "nrf_log_ctrl.h" #include "nrf_log_default_backends.h" static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0); #define PERIOD 1000 #define DUTY 75 #define HIGH (PERIOD * (100 - DUTY) / 100) //250 #define LOW PERIOD //1000 static nrf_pwm_values_individual_t /*const*/ seq_values[] = { {HIGH, LOW, LOW, LOW}, {HIGH, LOW, LOW, LOW}, {HIGH, LOW, LOW, LOW}, {HIGH, LOW, LOW, LOW}, {LOW, HIGH, LOW, LOW}, {LOW, HIGH, LOW, LOW}, {LOW, HIGH, LOW, LOW}, {LOW, HIGH, LOW, LOW}, }; nrf_pwm_sequence_t const seq = { .values.p_individual = seq_values, .length = NRF_PWM_VALUES_LENGTH(seq_values), .repeats = 0 , .end_delay = 0 }; static void demo(void) { nrf_drv_pwm_config_t const config0 = { .output_pins = { 3, 4, NRFX_PWM_PIN_NOT_USED, NRFX_PWM_PIN_NOT_USED }, .irq_priority = APP_IRQ_PRIORITY_LOWEST, .base_clock = NRF_PWM_CLK_1MHz, .count_mode = NRF_PWM_MODE_UP, .top_value = 1000, .load_mode = PWM_DECODER_LOAD_Individual, .step_mode = NRF_PWM_STEP_AUTO }; APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config0, NULL)); } void app_error_fault_handler(uint32_t id, uint32_t pc, uint32_t info) { app_error_save_and_stop(id, pc, info); } int main(void) { demo(); for (;;) { (void)nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 4 , NRFX_PWM_FLAG_STOP); nrf_delay_ms(1000); } } Note, I changed the pins so you should probably change them back ;) Instead of using the repeat, I hardcoded the sequence pattern and use the playback_count parameter to nrfx_pwm_simple_playback() to decide the number of times the pattern should be repeated. Here is a trace from the logic analyzer with playback_count set to 4: best regards Jared

John Lee · Answer

I solved it. Thank you for the answer.

Please give me advice on nrf pwm driver.

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