Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

RE: Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

haakonsh — Fri, 31 Aug 2018 07:37:59 GMT

Oh, yes there are 4 per timer, I think you should be able to use compare0 register if you change the capture task to register 1.

RE: Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

Jared — Fri, 31 Aug 2018 07:26:28 GMT

Thanks haakonsh

I was under the impression that there were 4 capture/compare registers per timer. I'm actually using the first CC channel for PWM clock generation.

Anyway thanks again for your help!

RE: Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

haakonsh — Fri, 31 Aug 2018 07:23:28 GMT

Seems you figured it out while i was typing my reply, see me previous reply :3

RE: Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

haakonsh — Fri, 31 Aug 2018 07:20:22 GMT

nrfx_timer_task_address_get(&m_counter, NRF_TIMER_TASK_CAPTURE0));

I think you'll need to use another capture register since you're using capture/compare register 0 for the compare event. What I think is happening is that the compare register is overwritten at every clock cycle by the capture task. Why do you need to capture the timer value anyways? It will trigger a compare event when it reaches the value of the capture/compare register 0.

RE: Count Clock Pulses with PPI + Gpiote Then Change GPIO Depending on Count (NRF52810)

Jared — Fri, 31 Aug 2018 07:18:48 GMT

Here's the magic incantation that I found worked.

The setup:

  uint32_t err;

  // change to coutner
  nrfx_timer_config_t tmr_config = NRFX_TIMER_DEFAULT_CONFIG;
  tmr_config.mode = NRF_TIMER_MODE_COUNTER;
  tmr_config.bit_width = NRF_TIMER_BIT_WIDTH_32;

  // TODO: Configure counter. No timeout handler.
  err = nrfx_timer_init(&m_counter, &tmr_config, timer_handler_count);
  VERIFY_SUCCESS(err);

  // Input & output configuration
  nrfx_gpiote_in_config_t in_config = NRFX_GPIOTE_CONFIG_IN_SENSE_LOTOHI(true);
  nrfx_gpiote_out_config_t out_config =
      NRFX_GPIOTE_CONFIG_OUT_TASK_TOGGLE(false);

  // Init GPIO pins
  err = nrfx_gpiote_in_init(LIS2DH_INT_PIN, &in_config, clk_in_pin_handler);
  VERIFY_SUCCESS(err);

  err = nrfx_gpiote_out_init(LED_TRANS_PIN, &out_config);
  VERIFY_SUCCESS(err);

  // Enable tasks
  nrfx_gpiote_in_event_enable(LIS2DH_INT_PIN, false);
  nrfx_gpiote_out_task_enable(LED_TRANS_PIN);

  // Configure GPIO high on counter compare event
  err = nrfx_ppi_channel_alloc(&m_latch_in_channel);
  VERIFY_SUCCESS(err);

  // Configure output after counter compare
  err = nrfx_ppi_channel_alloc(&m_latch_out_channel);
  VERIFY_SUCCESS(err);

  // Assign the channel, input event, then counts the timer
  err = nrfx_ppi_channel_assign(
      m_latch_in_channel, nrfx_gpiote_in_event_addr_get(LIS2DH_INT_PIN),
      nrfx_timer_task_address_get(&m_counter, NRF_TIMER_TASK_COUNT));
  VERIFY_SUCCESS(err);

  // Sets the state of the trans pin after count compare
  err = nrfx_ppi_channel_assign(
      m_latch_out_channel,
      nrfx_timer_event_address_get(&m_counter, NRF_TIMER_EVENT_COMPARE1),
      nrfx_gpiote_out_task_addr_get(LED_TRANS_PIN));
  VERIFY_SUCCESS(err);

Using it:

  // Enable these channels
  nrfx_ppi_channel_enable(m_latch_in_channel);
  nrfx_ppi_channel_enable(m_latch_out_channel);

  nrfx_gpiote_out_task_enable(LED_TRANS_PIN);

  // With reset.
  nrfx_timer_compare(&m_counter, NRF_TIMER_CC_CHANNEL1, 5, true);
  nrfx_timer_enable(&m_counter);
  nrfx_timer_clear(&m_counter);

  // The data!
  static uint8_t data[] = {0xaa, 0xaa};

  nrfx_spim_xfer_desc_t xfer_desc = NRFX_SPIM_XFER_TX(data, 2);

  // Transfer test 16 bits
  nrfx_spim_xfer(&spi, &xfer_desc, 0);

I was using the wrong compare event to toggle the output gpio. (should use nrfx_timer_event_address_get). To get the count I used this guy:

nrfx_timer_capture(&m_counter, NRF_TIMER_CC_CHANNEL1);

Toggles at te 5th bit as expected. Though a little delayed.