RE: Control of SS pin of SPI with ppi.

jaeheung — Wed, 05 Aug 2020 00:28:56 GMT

Hi.

I solved it by using GPIOTE as below.
Thank you for your advice.

void power_sampling_event_init(void)
{
{
    nrfx_gpiote_out_config_t config = NRFX_GPIOTE_CONFIG_OUT_TASK_TOGGLE(true);

    uint32_t start_task_addr = nrf_drv_spi_start_task_get(&heater_volt_spi);
    uint32_t gpiote_task_addr;

    err_code = nrf_drv_gpiote_out_init(SPI_nCS_RVAC, &config);
    APP_ERROR_CHECK(err_code);

    gpiote_task_addr = nrfx_gpiote_clr_task_addr_get(SPI_nCS_RVAC);

    err_code = nrf_drv_ppi_channel_alloc(&m_ppi_voltage_channel);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_assign(m_ppi_voltage_channel, timer2_compare_event_addr, start_task_addr);
    APP_ERROR_CHECK(err_code);
    
    err_code = nrf_drv_ppi_channel_fork_assign(m_ppi_voltage_channel, gpiote_task_addr);
    APP_ERROR_CHECK(err_code);
}


{
  uint32_t start_event_addr = nrf_drv_spi_end_event_get(&heater_volt_spi);
  uint32_t gpiote_task_addr;
  
  gpiote_task_addr = nrfx_gpiote_set_task_addr_get(SPI_nCS_RVAC);

  err_code = nrf_drv_ppi_channel_alloc(&m_ppi_voltage_nCS_channel);
  APP_ERROR_CHECK(err_code);
  
  err_code = nrf_drv_ppi_channel_assign(m_ppi_voltage_nCS_channel, start_event_addr, gpiote_task_addr);
  APP_ERROR_CHECK(err_code);

}

    err_code = nrf_drv_ppi_channel_enable(m_ppi_voltage_channel);
    APP_ERROR_CHECK(err_code);

    err_code = nrf_drv_ppi_channel_enable(m_ppi_voltage_nCS_channel);
    APP_ERROR_CHECK(err_code);
    
    nrf_drv_gpiote_out_task_enable(SPI_nCS_RVAC);

}

RE: Control of SS pin of SPI with ppi.

Jørgen Holmefjord — Tue, 07 Jul 2020 13:08:23 GMT

Hi,

You can use GPIOTE to toggle the SS pin, see the GPIOTE example on how to set that up. If the slave does not require any time between SS and SCK, you can trigger the GPIOTE task on the same NRF_TIMER_EVENT_COMPARE0 event (using PPI fork), or alternatively a separate TIMER COMPARE event set to trigger a given time before the SPI transfer triggering event.

Similarly, you can use the SPI END event to toggle the SS pin automatically again using GPIOTE after the transfer.

Best regards,
Jørgen