Software UART through emulated GPIO pins for nrf52833.

[Fernando Mercado]

Hi there,

Currently, I'm working on a solution where I need to design a software UART through emulated GPIO pins for nrf52833.

The requirements are that, solution would be all in bare-metal, I mean, without using the SDK.

Then, if you could help me with a good example or snippet of code to starting, I would appreciate your help.

Whatever advice you leave, it'll be received.

Thanks in advance.

[Felix Shih]

Hi,

ChatGPT gives the following reference code, and I don't test it, maybe not work. Just for your reference.

#include "nrf_gpio.h"
#include "nrf_timer.h"
#include "nrf_drv_timer.h"

#define TX_PIN 17
#define RX_PIN 18

volatile uint8_t tx_buffer = 0;
volatile uint8_t rx_buffer = 0;
volatile bool tx_ready = true;
volatile bool rx_ready = false;

void timer_handler(void) {
    if (tx_ready) {
        nrf_gpio_pin_toggle(TX_PIN);
        tx_ready = false;
    }
    if (rx_ready) {
        rx_ready = false;
        rx_buffer = nrf_gpio_pin_read(RX_PIN);
    }
}

void uart_send(uint8_t byte) {
    tx_buffer = byte;
    tx_ready = true;
}

uint8_t uart_receive(void) {
    while (!rx_ready) {
        // Wait for data to be ready
    }
    return rx_buffer;
}

void setup(void) {
    nrf_gpio_cfg_output(TX_PIN);
    nrf_gpio_cfg_input(RX_PIN, NRF_GPIO_PIN_PULLUP);
    nrf_drv_timer_init(&timer, NRF_TIMER_MODE_COMPARE, false, timer_handler);
    nrf_drv_timer_start(&timer, NRF_TIMER_TICKS_PER_US, false);
}

int main(void) {
    setup();
    while (1) {
        uart_send(0x55); // Send a byte
        uint8_t received_byte = uart_receive(); // Receive a byte
    }
}