SPIM RX started by ppi delay about 6us

RE: SPIM RX started by ppi delay about 6us

Håkon Alseth — Fri, 30 Oct 2020 08:45:11 GMT

If you look at figure 1 here in the GPIO chapter of the PS, the override signal from the peripheral is DIR_OVERRIDE and OUT_OVERRIDE, which disconnects the original GPIO configuration:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/gpio.html?cp=4_2_0_19#concept_zyt_tcb_lr

Kind regards,

Håkon

RE: SPIM RX started by ppi delay about 6us

xjhu — Fri, 30 Oct 2020 07:43:15 GMT

Thank you very much.

the 6us delay like disapeared after i turn off NRF_LOG_ENABLED = 0,there has a strange thing when i turn on NRF_LOG again,the delay still less than 2us.

[quote userid="2115" url="~/f/nordic-q-a/67648/spim-rx-started-by-ppi-delay-about-6us/277551#277551"]There's no guarantee that you can override a GPIO that has been claimed by a peripheral, especially an output configured one.[/quote]

are you mean there has no way to turn mosi high after spim enable?

RE: SPIM RX started by ppi delay about 6us

Håkon Alseth — Thu, 29 Oct 2020 09:37:48 GMT

Hi,

[quote user="xjhu"]like my first test code,i have called sd_power_mode_set(NRF_POWER_MODE_CONSTLAT).and it is no effect..[/quote]

This is strange. If you disable SD and use WFE, you get 2 us, which is still higher than what I get.

I integrated my test into ble_app_template, with NRF_LOG disabled, still get 1 us delay at my end. Could you try the algorithm I posted to see if this gets you the same timing?

[quote user="xjhu"]I modify nrfx_spim_init like below, and i got high first but return to low when call nrf_spim_enable(p_spim).I think maybe spim put mosi to low by default.[/quote]

I suspected this, unfortunately. The SPI module takes over the GPIOs and configures them towards how it should actively handle the pins. MOSI = master out, slave in, meaning its an output seen from the nRF's point-of-view, and it has been set to a defined level.

There's no guarantee that you can override a GPIO that has been claimed by a peripheral, especially an output configured one.

Kind regards,

Håkon

RE: SPIM RX started by ppi delay about 6us

xjhu — Thu, 29 Oct 2020 02:04:22 GMT

[quote userid="2115" url="~/f/nordic-q-a/67648/spim-rx-started-by-ppi-delay-about-6us/277403#277403"]Did you set the constlat power mode (sd_power_mode_set(NRF_POWER_MODE_CONSTLAT)) when testing this?[/quote]

like my first test code,i have called sd_power_mode_set(NRF_POWER_MODE_CONSTLAT).and it is no effect..

RE: SPIM RX started by ppi delay about 6us

xjhu — Thu, 29 Oct 2020 01:59:32 GMT

Hi,

I modify nrfx_spim_init like below, and i got high first but return to low when call nrf_spim_enable(p_spim).I think maybe spim put mosi to low by default.

if (p_config->mosi_pin != NRFX_SPIM_PIN_NOT_USED)
{
mosi_pin = p_config->mosi_pin;
nrf_gpio_pin_set(mosi_pin);//clear(mosi_pin);
nrf_gpio_cfg_output(mosi_pin);
}

RE: SPIM RX started by ppi delay about 6us

Håkon Alseth — Wed, 28 Oct 2020 13:37:17 GMT

Hi,

[quote user="xjhu"]

but when i enable SPIM this pin go to low immediately.

is it possible?

[/quote]

The nrfx_spim.c driver sets the default level in nrfx_spim_init. You can try to override this in the driver itself:

    if (p_config->mosi_pin != NRFX_SPIM_PIN_NOT_USED)
    {
        mosi_pin = p_config->mosi_pin;
        nrf_gpio_pin_clear(mosi_pin);
        nrf_gpio_cfg_output(mosi_pin);
    }

[quote user="xjhu"]but my project need support ble function and can not disable softdevice,is there any solution or method to avoid this kind of delay?[/quote]

Did you set the constlat power mode (sd_power_mode_set(NRF_POWER_MODE_CONSTLAT)) when testing this?

Kind regards,

Håkon

RE: SPIM RX started by ppi delay about 6us

xjhu — Wed, 28 Oct 2020 12:29:36 GMT

there also has another question,

my project need the MOSI pin be high level when SPIM is idle,

but when i enable SPIM this pin go to low immediately.

is it possible?if it is,then please let me know what i need to do.

RE: SPIM RX started by ppi delay about 6us

xjhu — Wed, 28 Oct 2020 12:17:24 GMT

when I switch off softdevice and other ble functions,use __WFE in main loop,I got 2us delay.

but my project need support ble function and can not disable softdevice,is there any solution or method to avoid this kind of delay?

thank you again.

RE: SPIM RX started by ppi delay about 6us

xjhu — Wed, 28 Oct 2020 12:07:33 GMT

HI Håkon Alseth，thanks your reply.

my code is tested under enable softdevice(S132-7.0.1) and setup ble functions.

I called idle_state_handle() in main loop.

static void idle_state_handle(void)
{
ret_code_t err_code;

err_code = nrf_ble_lesc_request_handler();
APP_ERROR_CHECK(err_code);

if (NRF_LOG_PROCESS() == false)
{
nrf_pwr_mgmt_run();
}
}

I will test your code and report the result.

RE: SPIM RX started by ppi delay about 6us

Håkon Alseth — Wed, 28 Oct 2020 09:28:23 GMT

Hi,

I setup a quick test related to your description, and I see a delay of approx. 1 us:

Here's my test source (based on peripherals/spi/ example in SDK 17):

/**
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 * All rights reserved.
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 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form, except as embedded into a Nordic
 *    Semiconductor ASA integrated circuit in a product or a software update for
 *    such product, must reproduce the above copyright notice, this list of
 *    conditions and the following disclaimer in the documentation and/or other
 *    materials provided with the distribution.
 *
 * 3. Neither the name of Nordic Semiconductor ASA nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * 4. This software, with or without modification, must only be used with a
 *    Nordic Semiconductor ASA integrated circuit.
 *
 * 5. Any software provided in binary form under this license must not be reverse
 *    engineered, decompiled, modified and/or disassembled.
 *
 * THIS SOFTWARE IS PROVIDED BY NORDIC SEMICONDUCTOR ASA "AS IS" AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY, NONINFRINGEMENT, AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL NORDIC SEMICONDUCTOR ASA OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#include "nrf_drv_spi.h"
#include "app_util_platform.h"
#include "nrf_gpio.h"
#include "nrf_delay.h"
#include "boards.h"
#include "app_error.h"
#include <string.h>
#include "nrf_log.h"
#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
#include "nrf_drv_gpiote.h"
#include "nrf_ppi.h"

#define SPI_INSTANCE  0 /**< SPI instance index. */
static const nrf_drv_spi_t spi = NRF_DRV_SPI_INSTANCE(SPI_INSTANCE);  /**< SPI instance. */
static volatile bool spi_xfer_done;  /**< Flag used to indicate that SPI instance completed the transfer. */

#define TEST_STRING "Nordic test long string for testing"
static uint8_t       m_tx_buf[] = TEST_STRING;           /**< TX buffer. */
static uint8_t       m_rx_buf[sizeof(TEST_STRING) + 1];    /**< RX buffer. */
static const uint8_t m_length = sizeof(m_tx_buf);        /**< Transfer length. */

/**
 * @brief SPI user event handler.
 * @param event
 */
void spi_event_handler(nrf_drv_spi_evt_t const * p_event,
                       void *                    p_context)
{
    spi_xfer_done = true;
    NRF_LOG_INFO("Transfer completed.");
    if (m_rx_buf[0] != 0)
    {
        NRF_LOG_INFO(" Received:");
        NRF_LOG_HEXDUMP_INFO(m_rx_buf, strlen((const char *)m_rx_buf));
    }
}

void ppi_setup(void)
{

    NRF_PPI->CH[0].EEP = (uint32_t) nrf_drv_gpiote_in_event_addr_get(SPI_MISO_PIN);
    NRF_PPI->CH[0].TEP = (uint32_t)(NRF_SPIM_Type *)&((spi.u.spim.p_reg)->TASKS_RESUME);
    NRF_PPI->CHENSET = PPI_CHENSET_CH0_Enabled << PPI_CHENSET_CH0_Pos;
}

int main(void)
{
    bsp_board_init(BSP_INIT_LEDS);

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    NRF_LOG_DEFAULT_BACKENDS_INIT();

    nrf_drv_gpiote_init();

    nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
    spi_config.ss_pin   = SPI_SS_PIN;
    spi_config.miso_pin = SPI_MISO_PIN;
    spi_config.mosi_pin = SPI_MOSI_PIN;
    spi_config.sck_pin  = SPI_SCK_PIN;
    APP_ERROR_CHECK(nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL));

    nrf_drv_gpiote_in_config_t cfg = NRFX_GPIOTE_CONFIG_IN_SENSE_HITOLO(true);
    cfg.pull = NRF_GPIO_PIN_PULLUP;
    nrfx_err_t err_code = nrf_drv_gpiote_in_init(SPI_MISO_PIN, &cfg, NULL);
    APP_ERROR_CHECK(err_code);
    nrf_drv_gpiote_in_event_enable(SPI_MISO_PIN, true);

    NRF_LOG_INFO("SPI example started.");
    ppi_setup();
    NRF_LOG_FLUSH();
    while (1)
    {
        // Reset rx buffer and transfer done flag
        memset(m_rx_buf, 0, m_length);
        spi_xfer_done = false;

        APP_ERROR_CHECK(nrf_drv_spi_transfer(&spi, m_tx_buf, m_length, m_rx_buf, m_length));
        nrf_spim_task_trigger(spi.u.spim.p_reg, NRF_SPIM_TASK_SUSPEND);
        while (!spi_xfer_done)
        {
            __WFE();
        }        

        bsp_board_led_invert(BSP_BOARD_LED_0);
        nrf_delay_ms(200);
    }
}

Since I do not have your full example, I'm not able to test the exact same setup as you, but the above seems to work as intended.

Kind regards,

Håkon