Code to test RP2040 UART FIFO level trigger settings

uart_fifo_test.c

#include <stdio.h>
#include "pico/stdlib.h"
#include "pico/time.h"
#include "pico/multicore.h"
#include "hardware/irq.h"
#include "hardware/uart.h"

#define UART_TX_ID uart1
#define UART_TX 4
#define UART_RX_ID uart0
#define UART_RX 1

uint rx_ints;
uint rx_bytes;

void uart_rx_handle() {
    rx_ints++;
    while(uart_is_readable(UART_RX_ID)) {
        uint8_t x = uart_getc(UART_RX_ID);

        rx_bytes++;
    }
}

// Run all UART TX stuff on second core
void core1_main() {
    uart_init(UART_TX_ID, 115200);
    gpio_set_function(UART_TX, GPIO_FUNC_UART);
    uart_set_hw_flow(UART_RX_ID, false, false);
    uart_set_fifo_enabled(UART_RX_ID, true);

    while (1) {
        uart_putc_raw(UART_TX_ID, 0x55);
    }
}

int main() {
    multicore_reset_core1();
    multicore_launch_core1(core1_main);

    stdio_init_all();

    // Set up UART
    uart_init(UART_RX_ID, 115200);
    gpio_set_function(UART_RX, GPIO_FUNC_UART);
    uart_set_hw_flow(UART_RX_ID, false, false);
    uart_set_fifo_enabled(UART_RX_ID, true);


    // Set up interrupt
    int UART_IRQ = UART_RX_ID == uart0 ? UART0_IRQ : UART1_IRQ;

    irq_set_exclusive_handler(UART_IRQ, uart_rx_handle);
    irq_set_enabled(UART_IRQ, true);

    while(1) {
        for (int i=UART_FIFO_LEVEL_1_8; i<=UART_FIFO_LEVEL_7_8; i++) {
            rx_ints = 0;
            rx_bytes = 0;

            // Run for 1 second
            while(uart_is_readable(UART_RX_ID)) uart_getc(UART_RX_ID);
            uart_set_irq_enables(UART_RX_ID, true, false);
            uart_set_irq_fifo_levels(UART_RX_ID, i, i);
            sleep_ms(1000);
            uart_set_irq_enables(UART_RX_ID, false, false);

            float avg = (float) rx_bytes / (float) rx_ints;

            switch (i) {
                case UART_FIFO_LEVEL_1_8:
                    printf("FIFO Trigger 1/8");
                    break;
                case UART_FIFO_LEVEL_1_4:
                    printf("FIFO Trigger 1/4");
                    break;
                case UART_FIFO_LEVEL_1_2:
                    printf("FIFO Trigger 1/2");
                    break;
                case UART_FIFO_LEVEL_3_4:
                    printf("FIFO Trigger 3/4");
                    break;
                case UART_FIFO_LEVEL_7_8:
                    printf("FIFO Trigger 7/8");
                    break;
            }

            printf(", average bytes per interrupt: %f, bytes: %d, interrupts: %d\n", avg, rx_bytes, rx_ints);

            sleep_ms(500);
        }
    }

    return 0;
}