++ MbedOS Error Info ++
Error Status: 0x80FF0100 Code: 256 Module: 255
Error Message: Fatal Run-time error
Location: 0x80038F3
Error Value: 0x0
For more info, visit: https://mbed.com/s/error?error=0x80FF0100&tgt=NUCLEO_G031K8
-- MbedOS Error Info --
I2C: unknown instance

#include "I2CSlave.h"
#include "I2C.h"
#include <cstdio>
#include <string.h>
#define SLAVE_ADDR 0xA0
#define BUFFER_SIZE 6

I2C master(A4,A5);

static const char* to_send[] = { "abcde", "12345", "EFGHI" };

int main() {
    char buf[BUFFER_SIZE];
    int send_index = 0;
    while (1) {
        strcpy(buf, to_send[send_index]);
        // Write the new message to the slave
        if (master.write(SLAVE_ADDR, buf, BUFFER_SIZE)) {
            printf("Failed to write to slave!\n");
        } else {
            printf("Written to slave: %s\n", buf);
        }
        // Read what the slave has (should be identical)
        if (master.read(SLAVE_ADDR, buf, BUFFER_SIZE)) {
            printf("Failed to read from slave!\n");
        } else {
            printf("Read from slave: %s\n", buf);
        }
        // Change the message we're writing to the slave
        send_index++;
        if (send_index > 2) {
            send_index = 0;
        }
        wait_us(500000); // Wait 0.5s
    }
}