RE: Unexpected RXDRDY count

user69773 — Thu, 16 Jun 2022 07:20:36 GMT

user14926 Any update on this?

RE: Unexpected RXDRDY count

user69773 — Tue, 14 Jun 2022 15:50:30 GMT

Here's the relevant code:

    //Configure RX count timer
    nrfx_timer_config_t tmr_config_count = NRFX_TIMER_DEFAULT_CONFIG;
    tmr_config_count.mode = NRF_TIMER_MODE_COUNTER;
    tmr_config_count.p_context = (void *)p_serial;
    ret = nrfx_timer_init(p_serial->p_timer_rxcount, &tmr_config_count, timer_rxcount_evt_handler);
    if (ret != NRFX_SUCCESS)
        return NRF_ERROR_INTERNAL;
    nrfx_timer_enable(p_serial->p_timer_rxcount);

    //Configure RX timeout timer
    nrfx_timer_config_t tmr_config_timeout = NRFX_TIMER_DEFAULT_CONFIG;
    tmr_config_timeout.frequency = NRF_TIMER_FREQ_1MHz;
    tmr_config_timeout.p_context = (void *)p_serial;
    ret = nrfx_timer_init(p_serial->p_timer_rxtimeout, &tmr_config_timeout, timer_rxtimeout_evt_handler);
    if (ret != NRFX_SUCCESS)
        return NRF_ERROR_INTERNAL;
    nrfx_timer_compare(p_serial->p_timer_rxtimeout, NRF_TIMER_CC_CHANNEL0, p_config->timeout_us, false);

    // ...
    
    //  When a byte is received, increment RX count timer
    PPI_CH_SETUP(p_serial->p_ctrl_blk->ppi_channels[SERIALPORT_PPI_CH_0],
                 nrf_uarte_event_address_get(p_serial->uarte, NRF_UARTE_EVENT_RXDRDY),
                 nrfx_timer_task_address_get(p_serial->p_timer_rxcount, NRF_TIMER_TASK_COUNT),
                 NULL);
    //  When a byte is received, restart RX timeout timer
    PPI_CH_SETUP(p_serial->p_ctrl_blk->ppi_channels[SERIALPORT_PPI_CH_1],
                 nrf_uarte_event_address_get(p_serial->uarte, NRF_UARTE_EVENT_RXDRDY),
                 nrfx_timer_task_address_get(p_serial->p_timer_rxtimeout, NRF_TIMER_TASK_START),
                 nrfx_timer_task_address_get(p_serial->p_timer_rxtimeout, NRF_TIMER_TASK_CLEAR));
    //  On RX timeout timer compare, stop it and stop UART RX
    PPI_CH_SETUP(p_serial->p_ctrl_blk->ppi_channels[SERIALPORT_PPI_CH_2],
                 nrfx_timer_compare_event_address_get(p_serial->p_timer_rxtimeout, 0),
                 nrfx_timer_task_address_get(p_serial->p_timer_rxtimeout, NRF_TIMER_TASK_STOP),
                 nrf_uarte_task_address_get(p_serial->uarte, NRF_UARTE_TASK_STOPRX));

When the RX timeout timer compares, it triggers the STOPRX task on the UARTE.

My RXTO irq handler then reads the RXD.AMOUNT register and the value of the other timer which I use to count the RXDRDY events.

On that image, no more bytes are sent when the RTS is deasserted.

No, I don't trigger FLUSHRX. If there's extra data in the RX FIFO, I'm fine with it being read when I setup the next DMA transaction, but I need to know if there's data there so I can manually restart the RX timeout timer. I need to do that because I manually stop the RX timeout timer at the beginning of the RXTO handler. Which, in turn, I do because the RX timeout timer is stopped by PPI on the RX timeout timer Compare event, but up to 4 extra bytes could be received, and those RXDRDY events would make PPI restart the RX timer.

It's a bit mind-bending, I hope that makes sense.

But I just want to know when the RXDRDY event is triggered. It appears it's not when the stop bit is received at the RX pin, like the docs suggest.

RE: Unexpected RXDRDY count

user14926 — Tue, 14 Jun 2022 15:05:08 GMT

Hi,

Can you post your code showing how you configure the timer to count the events, and how you do the timeout?

Hard to see from your image, but is any of the bytes sent right after the RTS line is deactivated? The UART(E) peripheral has a HW RX FIFO that can hold up to 4 bytes, as described in the peripheral documentation. Do you trigger the STOPRX and/or FLUSHRX task at any point?

Best regards,
Jørgen