UARTE isn't working

[George555]

Hi. I'm writing my own libraries for nRF52832 and I can't get UARTE to work.

Here is my code.

I'm using pins 6 and 8 as the UART example.

I wrote same code for UART (without DMA) and it works fine!

uart.c file

#include <string.h>
#include <stdbool.h>
#include "nrf52.h"
#include "uart.h"

static volatile uint8_t tx_buffer[128];

void uart_set_baudrate(uint32_t val)
{
    NRF_UARTE0->BAUDRATE = val;
}

void uart_configure(uint32_t parity, uint32_t hwfc)
{
    NRF_UARTE0->CONFIG = (parity << UART_CONFIG_PARITY_Pos) | (hwfc << UART_CONFIG_HWFC_Pos);
}

void uart_set_pins(uint32_t txpin, uint32_t rxpin)
{
    NRF_UARTE0->PSEL.RXD = rxpin;
    NRF_UARTE0->PSEL.TXD = txpin;
}

void uart_enable(void)
{
    NRF_UARTE0->ENABLE = UART_ENABLE_ENABLE_Enabled;
}

void uart_init(void)
{
    uart_set_baudrate(UART_BAUDRATE_BAUDRATE_Baud115200);
    uart_configure(UART_CONFIG_PARITY_Excluded, UART_CONFIG_HWFC_Disabled);
    uart_set_pins(6, 8);
    uart_enable();
}

void uart_write_string(uint8_t * str, int size)
{
    memcpy(tx_buffer, str, size);
    NRF_UARTE0->TXD.PTR = (uint32_t)((uint8_t *)tx_buffer);
    NRF_UARTE0->TXD.MAXCNT = size;
    NRF_UARTE0->TASKS_STARTTX = 1;
}

main.c

int main(void)
{
    clock_init();
    rtc_init();

    gpio_out_set(6);
    gpio_config_output(6);
    gpio_config_input(8, GPIO_PIN_CNF_PULL_Disabled);
    
    uart_init();
    uart_write_string("Hello world\r\n", 14);
    radio_init();
    
    __enable_irq();

    while (true)
    {

    }
}

I don't get anything on the terminal.

[hmolesworth]

Try this code then compare with yours, for example start without flow control - like this code - and incrementally add features. Some of the steps here are not strictly necessary, but this works.

static NRF_UARTE_Type *pUART = NRF_UARTE0;
#define UART_TX 6
#define UART_RX 8

static void UartTransmit(uint8_t *pMsg, uint16_t MsgLength)
{
   // Disable the UARTE
   pUART->ENABLE = 0;

   // Configure UARTE with no flow control, no parity bit and 230400 baud rate
   pUART->CONFIG = 0;
   pUART->BAUDRATE = NRF_UART_BAUDRATE_230400;

   // Select TX and RX pin default disconnected mode to avoid sending break indication on disabling uart
   nrf_gpio_cfg(UART_RX, NRF_GPIO_PIN_DIR_INPUT,  NRF_GPIO_PIN_INPUT_CONNECT,    NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_S0S1, NRF_GPIO_PIN_NOSENSE);
   nrf_gpio_cfg(UART_TX, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0H1, NRF_GPIO_PIN_NOSENSE);

   // Select TX and RX pins
   pUART->PSEL.TXD = UART_TX;
   pUART->PSEL.RXD = UART_RX;

   // Disable all interrupts and clear events
   pUART->INTENCLR = 0xFFFFFFFFUL;
   pUART->EVENTS_TXSTARTED = 0;
   pUART->EVENTS_TXSTOPPED = 0;
   pUART->EVENTS_RXSTARTED = 0;
   pUART->EVENTS_ENDTX = 0;
   pUART->EVENTS_ENDRX = 0;

   // Enable the UART, note 0x04 for UART and 0x08 for UARTE with DMA
   pUART->ENABLE = 0x08;

   // Configure transmit buffer and start the transfer
   pUART->TXD.MAXCNT = MsgLength;
   pUART->TXD.PTR    = (uint32_t)pMsg;
   pUART->TASKS_STARTTX = 1;
   __DSB();
   // Wait until the transfer start event is indicated
   while (pUART->EVENTS_TXSTARTED == 0) ;

   // Wait until the transfer is complete
   while (pUART->EVENTS_ENDTX == 0) ;

   // Stop the UART TX
   pUART->TASKS_STOPTX = 1;
   __DSB();
   // Wait until we receive the stopped event
   while (pUART->EVENTS_TXSTOPPED == 0) ;

   // Disable the UARTE
   pUART->ENABLE = 0;

   // De-Select TX and RX pins
   pUART->PSEL.TXD = 0x80000000;
   pUART->PSEL.RXD = 0x80000000;
}

This code enables the UARTE0, transmits a string, then disables UARTE0 and releases the port pins so they can be used by other devices - such as (say) remote wakeup

[George555]

So far, I'm trying to see the "Hello world\r\n" on the terminal. It should transmit the string once the chip restarts.

I still don't understand why the UART peripheral worked fine but UARTE does not.

According to the datasheet the transmission initialized by setting up the TXD pointer and the size and triggering the STARTTX task

strcpy(tx_buffer, "Hello world\r\n");

NRF_UARTE0->TXD.PTR = (uint32_t)((uint8_t *)tx_buffer);

NRF_UARTE0->TXD.MAXCNT = 14;

NRF_UARTE0->TASKS_STARTTX = 1;

[hmolesworth]

Did you try the code I posted? It works with UARTE0. Note my comments about enabling the UART; what is the value of UART_ENABLE_ENABLE_Enabled? The value to enable the uart is different for UARTE compared with UART as I state in the code I posted.

[George555]

I changed all the flags from UART_ to UARTE_ and it works!

Thanks for noticing the UART_ENABLE_ENABLE_Enabled. It is different. It didn't solve the problem but after changing all the flags to UARTE it worked!

Thank you very much !!

PS: I couldn't try the code you posted cause I don't use SDK at all.

I only use the necessary files (bitfields, peripheral pointers etc) to get it work.