How to configure the UARTE0 correct?

[Philippe]

Hi all

I'm struggling with the easyDMA UART of nrf52. I've got a preview nrf52-DK here where I wanted to make a simple example with the following code but I never reach the ENDRX event even if I send 20 or more bytes to the DK (pin 8). Also in debug mode I can't see that any byte reaches the rxbuffer.

Do you guys see why is that? What did I make wrong in the initiation?

Thank you all in advance for your support!

#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include "nrf_delay.h"
#include "nrf_gpio.h"
#include "boards.h"
#include "nrf_uarte.h"

const uint8_t leds_list[LEDS_NUMBER] = LEDS_LIST;

void UARTE0_UART0_IRQHandler(){

	if(NRF_UARTE0->EVENTS_ENDRX){
		LEDS_INVERT(1 << leds_list[3]);
	}

}


int main(void)
{

	uint8_t txBuffer[20] = {0};
	uint8_t rxBuffer[20] = {0};

    NRF_UARTE0->BAUDRATE = NRF_UARTE_BAUDRATE_9600;
    NRF_UARTE0->PSEL.TXD = TX_PIN_NUMBER;
    NRF_UARTE0->PSEL.RXD = RX_PIN_NUMBER;
    NRF_UARTE0->CONFIG = NRF_UARTE_HWFC_DISABLED;
    NRF_UARTE0->ENABLE = (UARTE_ENABLE_ENABLE_Enabled << UARTE_ENABLE_ENABLE_Pos);

    NRF_UARTE0->TXD.PTR = (uint32_t)((uint8_t *) txBuffer);
    NRF_UARTE0->TXD.MAXCNT = sizeof(txBuffer);
    NRF_UARTE0->TASKS_STARTTX = 0;

    NRF_UARTE0->RXD.PTR = (uint32_t)((uint8_t *) rxBuffer);
    NRF_UARTE0->RXD.MAXCNT = sizeof(rxBuffer);
    NRF_UARTE0->TASKS_STARTRX = 1;


    NRF_UARTE0->INTENCLR = 0xFFFFFFFF;
    NRF_UARTE0->INTENSET = NRF_UARTE_INT_ENDRX_MASK;

    NVIC_ClearPendingIRQ(UARTE0_UART0_IRQn);
    NVIC_SetPriority(UARTE0_UART0_IRQn, 1);
    NVIC_EnableIRQ(UARTE0_UART0_IRQn);



    // Configure LED-pins as outputs.
    LEDS_CONFIGURE(LEDS_MASK);
    if(NRF_UARTE0->EVENTS_RXSTARTED){
    	LEDS_INVERT(1 << leds_list[1]);
    }


    while (true)
    {


    }
}

[Vidar Berg]

Hi, ran the exact same code on the preview kit and did receive the EVENTS_ENDRX with the correct data. Have you checked if tx works?

Description of my setup:

• on board Segger chip used as usb<->uart bridge
• Terra term (serial terminal) on windows 7

Just a note, generally you should have static allocation of your buffers, Although it shouldn't be a problem in this example.

Attachment:

• uart example

[Eric Stutzenberger]

Agreed with static allocation. It's very important. If you were to move this setup code out of main and into its own function, the buffers will need to be declared static (or allocated with alloc()). If this is not done, then the buffers will not exist and the DMA will potentially overwrite the memory of some other data in the system.