nRF52840 SPIS semaphore acquire and release

RE: nRF52840 SPIS semaphore acquire and release

Olly_OB — Wed, 03 Mar 2021 15:07:01 GMT

I've managed to solve my issue with the ACQUIRE event, so I'll post some information here in case it helps someone else in the future.

Background
I was working on implementing SPIS functionality for the NRF52832 within Mbed OS. This involved working through the targets/.../TARGET_MCU_NRF52832/spi_api.c file within Mbed and trying to add SPIS functionality around the existing SPI/SPIM functionality.

Problem

The program would hang whenever I ran nrfx_spis_buffers_set(). Digging further down, I found that the program would trigger the task to acquire the semaphore, nrf_spis_task_trigger(p_spis, NRF_SPIS_TASK_ACQUIRE), however the spis_irq_handler() would never be called.

Solution

After too many days of investigation, I found that I had not registered the interrupt handlers in the driver with the NVIC.

Simply put, I should have called:

NVIC_SetVector(SPIM0_SPIS0_TWIM0_TWIS0_SPI0_TWI0_IRQn, (uint32_t) SPIM0_SPIS0_TWIM0_TWIS0_SPI0_TWI0_IRQHandler)

Before calling:

nrfx_spis_buffers_set()

I appreciate that this may be more of an Mbed OS issue, however there seems to have been a number of people that have experienced this issue, so I wanted to leave it here anyway, just in case others find it useful.

RE: nRF52840 SPIS semaphore acquire and release

Einar Thorsrud — Wed, 24 Feb 2021 12:36:51 GMT

Hi,

It is not easy to see if this is the same issue as you are seeing or not. I suggest you create a new question where you explain the issue you are seeing in more detail in order to look at that specifically. (There you could refer to this thread.)

RE: nRF52840 SPIS semaphore acquire and release

Olly_OB — Tue, 23 Feb 2021 21:29:24 GMT

I know this is a long shot, but I'm experiencing the exact same issue, and it appears that a lot of people have also encountered this. Does anyone know of the solution?

I've gone through and confirmed that SPIS has been successfully configured before the CS line is being pulled low. However it appears that I'm unable to ACQUIRE the semaphore.

RE: nRF52840 SPIS semaphore acquire and release

Narayanan — Wed, 17 Jul 2019 22:57:18 GMT

Any conclusion on this case? I am running into exactly same issue.

RE: nRF52840 SPIS semaphore acquire and release

donbosley — Mon, 18 Mar 2019 21:17:54 GMT

Is there any chance or a hardware or resource conflict based on the SPI in use - I had different behavior result from using SPI1 vs using SPI 0 - in SPIS1 I never entered the handler (tried using a breakpoint in ozone as well as an NRF LOG). When I switched to 0, it entered handler. When I added code to refresh the buffer pointers in the event handler it started working as expected.

RE: nRF52840 SPIS semaphore acquire and release

Tech — Fri, 18 Jan 2019 15:41:33 GMT

Hi All,

I am using the nRF52840 with SDK140 v15.2. I have configured the nRF52840 to be a SPI slave as you did. I am experiencing the same problem you had. Did you solved the problem? Can you tell me what you did?

Thank you in advance.

RE: nRF52840 SPIS semaphore acquire and release

MartinBL — Tue, 23 Oct 2018 08:55:22 GMT

Is the code getting stuck at the very first transmission?

Can you confirm that the SPIS has been successfully configured before the CS line is being pulled low?

If you debug your application (using a debugger and not printfs), where exactly does your code end up?

RE: nRF52840 SPIS semaphore acquire and release

Saili — Fri, 19 Oct 2018 16:09:46 GMT

Hi,

The "Enable" trace in the scope capture above is the CS line, which is low in the trace. I posted a zoomed in version so that the data sent on the MOSI line was visible/ readable. Here is a zoomed out version showing the CS line (Enable trace) going low before the start of transaction and going high after the end of SPI transaction. Attached is the zoomed out trace.

The code does not crash but just is waiting for ever. And yes, like you pointed out there is not much that can go wrong with the function that is why I am stumped. I am also checking the error codes but I might be missing something, hence I have attached the code.

static void _run_spi_slave_loopback_test(void)
{
    uint32_t nrf_err = NRF_SUCCESS;

    LOG_INFO("Starting SPIS demo, press button 3 to exit...");

    if (!_spi_slave_initialized)
    {
        static const nrfx_gpiote_out_config_t slave_pin_config = NRFX_GPIOTE_CONFIG_OUT_SIMPLE(true);

        snprintf((char *)_m_tx_buf, 127, "%s", TEST_STRING);

        if (nrfx_gpiote_out_init(PIN_MAP_SPIS_SLAVE_READY_PIN, &slave_pin_config) != (ret_code_t) NRF_SUCCESS)
        {
            LOG_ERROR("Failed to initialize SRDY pin");
            goto rsslt_exit;
        }

        // initialize the SPI slave driver
        nrfx_spis_config_t spis_config = { .sck_pin = PIN_MAP_SPIS1_CONFIG_SCK_PIN,
                                              .mosi_pin = PIN_MAP_SPIS1_CONFIG_MOSI_PIN,
                                              .miso_pin = PIN_MAP_SPIS1_CONFIG_MISO_PIN,
                                              .csn_pin = PIN_MAP_SPIS1_CONFIG_PCS_PIN,
                                              .miso_drive = NRFX_SPIS_DEFAULT_MISO_DRIVE,
                                              .csn_pullup = NRFX_SPIS_DEFAULT_CSN_PULLUP,
                                              .orc = SPIS_DEFAULT_ORC,
                                              .def = SPIS_DEFAULT_DEF,
                                              .mode = NRF_SPIS_MODE_0,
                                              .bit_order = NRF_SPIS_BIT_ORDER_MSB_FIRST,
                                              .irq_priority = PIN_MAP_SPIS1_CONFIG_IRQ_PRIORITY };

        nrf_err = nrfx_spis_init(&_spis, &spis_config, _spis_event_handler, NULL);
        if (nrf_err != NRF_SUCCESS)
        {
            LOG_ERROR("Failed to initialize SPIS");
            goto rsslt_exit;
        }
        _spi_slave_initialized = true;
    }

    while (1)
    {
        memset(_m_rx_buf, 0, _m_length);
        _spis_xfer_done = false;

        nrf_err = nrfx_spis_buffers_set(&_spis, _m_tx_buf, _m_length, _m_rx_buf, _m_length);
        if (nrf_err != NRF_SUCCESS)
        {
            LOG_ERROR("Failed to set SPIS buffers");
            goto rsslt_exit;
        }

        while (!_spis_xfer_done)
        {
            if (bsp_button_pressed(BSP_BUTTON_3))
            {
                LOG_INFO("Button 3 pressed, stopping demo");
                goto rsslt_exit;
            }

            nrf_delay_us(10);
        }

        if (_spis_xfer_done)
        {
            LOG_INFO("Transfer completed. Received: %s", _m_rx_buf);
            LOG_INFO("Toggling SRDY pin for 1ms as a test.");
            nrfx_gpiote_out_clear(PIN_MAP_SPIS_SLAVE_READY_PIN);
            nrf_delay_ms(1);
            nrfx_gpiote_out_set(PIN_MAP_SPIS_SLAVE_READY_PIN);
        }
    }

RE: nRF52840 SPIS semaphore acquire and release

MartinBL — Fri, 19 Oct 2018 12:14:53 GMT

You write that you can see the CS line goes low, but I don't see it in the logic trace. When does it happen? Is it possible that your problem is related to this? You will need to pull the CS pin low after SPIS is initialized in order to aquire the semaphore.

Furthermore, by "gets stuck at nrf_spis_task_trigger" I assume you mean that the code is "stuck" waiting for the semaphore and not actually crashing inside that function? There doesn't seem to be much that can go wrong inside it:

__STATIC_INLINE void nrf_spis_task_trigger(NRF_SPIS_Type * p_reg,
                                           nrf_spis_task_t spis_task)
{
    *((volatile uint32_t *)((uint8_t *)p_reg + (uint32_t)spis_task)) = 0x1UL;
}

If neither of this is helping:

Are you checking the return code of all the functions in your code?
Can you upload your code?