How can I implement UART RX PPI with GPIO?

RE: How can I implement UART RX PPI with GPIO?

Vidar Berg — Wed, 17 Aug 2022 10:57:50 GMT

Hello,

I see the problem now. To enable reception you have to provide the driver with a application buffer to hold store the received bytes. You also have to repeat this after receiving the NRFX_UART_EVT_RX_DONE event.

Like this:

static uint8_t m_rx_buffer[1];

void UART_dataHandler(void)
{
    ...
    nrfx_uart_rx(&uart1_inst, m_rx_buffer, sizeof(m_rx_buffer));
}

int main(void)
{
    uart1_init();
    
    ppi_init();
    nrfx_uart_rx(&uart1_inst, m_rx_buffer, sizeof(m_rx_buffer));
    
    while(1)
    {}
}

You may also refer to the app_uart library implementation used by ble_app_uart to see how the driver APIs are used there.

RE: How can I implement UART RX PPI with GPIO?

William_dev — Fri, 12 Aug 2022 00:03:22 GMT

Hello,

Here the related UART code initial part, IRQ handler, main

void UART_dataHandler(void)
{
    static uint8_t databuff;
    printf("%x\r\n", databuff);
}

void UART_idleHandler(void)
{
}
/*    UART ISR    */
void UART_IRQ_handler(const nrfx_uart_event_t * p_event, void * p_context)
{
    switch(p_event -> type)
    {
        case NRFX_UART_EVT_RX_DONE:
            UART_dataHandler();
            break;
        case NRFX_UART_EVT_TX_DONE:
            break;
        case NRFX_UART_EVT_ERROR:
            NRF_LOG_INFO("INVALID_IRQ\r\n");
            UART_idleHandler();
            break;
    }
}

void uart1_init(void)
{
    uint32_t err_code;

    nrfx_uart_config_t uart1_config = {TX_PIN,
                                       RX_PIN,
                                       CTS_PIN,
                                       RTS_PIN,
                                       NULL,
                                       NRF_UART_HWFC_DISABLED,
                                       NRF_UART_PARITY_EXCLUDED,
                                       UART_BR_115200,
                                       6};

    nrfx_uart_init(&uart1_inst, &uart1_config, UART_IRQ_handler);
    nrf_uart_int_enable(NRF_UART0, NRF_UART_INT_MASK_ERROR | NRF_UART_INT_MASK_RXDRDY);
    nrf_uart_event_clear(NRF_UART0, NRF_UART_EVENT_ERROR | NRF_UART_EVENT_RXDRDY);
    //nrf_uart_task_trigger(NRF_UART0, NRF_UART_TASK_STARTRX);
}

static void ppi_init()
{
        uint32_t err_code;

        uint32_t uart_event_addr;
        uint32_t gpio_task_addr;
        
        nrf_ppi_channel_t ppi_channel_uart_gpio_toggle;

        err_code = nrf_drv_ppi_init();
        if((err_code != 0) && (err_code != NRF_ERROR_MODULE_ALREADY_INITIALIZED))
        {
            APP_ERROR_CHECK(err_code);
        }

        nrf_drv_gpiote_out_config_t config = GPIOTE_CONFIG_OUT_TASK_TOGGLE(true);

        err_code = nrfx_gpiote_out_init(LED_1, &config);
        APP_ERROR_CHECK(err_code);

        err_code = nrfx_ppi_channel_alloc(&ppi_channel_uart_gpio_toggle);
        APP_ERROR_CHECK(err_code);

        uart_event_addr = nrfx_uart_event_address_get(&uart1_inst, NRF_UART_EVENT_RXDRDY);
        gpio_task_addr = nrfx_gpiote_out_task_addr_get(LED_1);
        
        err_code = nrfx_ppi_channel_assign(ppi_channel_uart_gpio_toggle, uart_event_addr, gpio_task_addr);
        APP_ERROR_CHECK(err_code);

        err_code = nrfx_ppi_channel_enable(ppi_channel_uart_gpio_toggle);
        APP_ERROR_CHECK(err_code);

        nrfx_gpiote_out_task_enable(LED_1);
}

int main(void)
{
    uart1_init();
    
    ppi_init();
    nrfx_uart_rx_enable(&uart1_inst);
    
    while(1)
    {}
}

RE: How can I implement UART RX PPI with GPIO?

Vidar Berg — Thu, 11 Aug 2022 19:04:40 GMT

Hello,

Would you mind sharing the rest of the UART related code? I am not sure I understand exactly how you have configured it now, or why you only get the first RX byte event.

RE: How can I implement UART RX PPI with GPIO?

William_dev — Thu, 11 Aug 2022 08:29:35 GMT

Hi, I appreciate to your reply.

Let me go back to second question.

I tried UARTE but It cause matter to system that I designed.

As, is there any answer use UART peripheral?

The matter is when I receive one byte, just LED toggle once. And receive next one byte, there's no response to LED.

Plz check the code below.

void ppi_init()
{
            uint32_t err_code;

            uint32_t uart_event_addr;
            uint32_t gpio_task_addr;
            
            nrf_ppi_channel_t ppi_channel_uart_gpio_toggle;
    
            err_code = nrf_drv_ppi_init();
            if((err_code != 0) && (err_code != NRF_ERROR_MODULE_ALREADY_INITIALIZED))
            {
                APP_ERROR_CHECK(err_code);
            }
    
            nrf_drv_gpiote_out_config_t config = GPIOTE_CONFIG_OUT_TASK_TOGGLE(0);
    
            err_code = nrf_drv_gpiote_out_init(LED_1, &config);
            APP_ERROR_CHECK(err_code);
    
            err_code = nrf_drv_ppi_channel_alloc(&ppi_channel_uart_gpio_toggle);
            APP_ERROR_CHECK(err_code);
    
            uart_event_addr = nrfx_uart_event_address_get(&uart1_inst, NRF_UART_EVENT_RXDRDY);
            gpio_task_addr = nrfx_gpiote_out_task_addr_get(LED_1);
            
            err_code = nrfx_ppi_channel_assign(ppi_channel_uart_gpio_toggle, uart_event_addr, gpio_task_addr);
            APP_ERROR_CHECK(err_code);
    
            err_code = nrf_drv_ppi_channel_enable(ppi_channel_uart_gpio_toggle);
            APP_ERROR_CHECK(err_code);
    
            nrfx_gpiote_out_task_enable(LED_1);
}

Best regards,

William.

RE: How can I implement UART RX PPI with GPIO?

Vidar Berg — Thu, 11 Aug 2022 06:44:26 GMT

DMA is mandatory with UARTE, but that does not mean you will not get an interrupt. You can set the DMA receive buffer to '1' byte if you want the uarte driver callback to be called for every received byte.

RE: How can I implement UART RX PPI with GPIO?

William_dev — Thu, 11 Aug 2022 01:29:14 GMT

Hello,

I studied UART, UARTE's difference. UARTE is added EasyDMA to UART.

However, I use UART peripheral IRQ, with Timer PPI. Can I use UARTE peripheral IRQ not DMA?

RE: How can I implement UART RX PPI with GPIO?

Vidar Berg — Tue, 09 Aug 2022 06:23:16 GMT

Hello,

Please try to use the UARTE peripheral instead (i.e. UARTE — Universal asynchronous receiver/transmitter with EasyDMA) and not UART — Universal asynchronous receiver/transmitter). The legacy UART will only trigger the RXDRDY event after the byte has been moved to the RXD register as noted here in the PS:

The UART receiver chain implements a FIFO capable of storing six incoming RXD bytes before data is overwritten. Bytes are extracted from this FIFO by reading the RXD register. When a byte is extracted from the FIFO a new byte pending in the FIFO will be moved to the RXD register. The UART will generate an RXDRDY event every time a new byte is moved to the RXD register. (Reception)

RE: How can I implement UART RX PPI with GPIO?

William_dev — Tue, 09 Aug 2022 05:12:38 GMT

This time, just once toggle as UART event done.

How can I toggle LED at every UART RX event use the ppi?

RE: How can I implement UART RX PPI with GPIO?

William_dev — Tue, 09 Aug 2022 01:02:48 GMT

Hello, Vidar

Thank for your advice.

It works changed TASK_STARTRX to EVENT_RXDRDY.

RE: How can I implement UART RX PPI with GPIO?

Vidar Berg — Mon, 08 Aug 2022 12:15:42 GMT

Hello,

You are retrieving the task address here:

uart_event_addr = nrfx_uart_event_address_get(&uart1_inst, NRF_UART_TASK_STARTRX);

while it should have been

uart_event_addr = nrfx_uart_event_address_get(&uart1_inst, NRF_UART_EVENT_RXDRDY);

Hope this helps.

Best regards,

Vidar