Converting user input to hex - ESP32 IDF - c

Question

I'm trying to build a function that accepts commands using UART and extracts a sub string from the command to write it into ESP32 EFUSE.
static void uart_event_task()
{
uart_event_t event;
size_t buffered_size;
uint8_t *dtmp = (uint8_t *)malloc(RD_BUF_SIZE);
char cmd[30];
char serialNum[20];
for (;;)
{
// Waiting for UART event.
if (xQueueReceive(uart0_queue, (void *)&event, (TickType_t)portMAX_DELAY))
{
bzero(dtmp, RD_BUF_SIZE);
ESP_LOGI(TAG_CONFIG, "uart[%d] event:", EX_UART_NUM);
switch (event.type)
{
// Event of UART receving data
/*We'd better handler data event fast, there would be much more data events than
other types of events. If we take too much time on data event, the queue might
be full.*/
case UART_DATA:
ESP_LOGI(TAG_CONFIG, "[UART DATA]: %d", event.size);
uart_read_bytes(EX_UART_NUM, dtmp, event.size, portMAX_DELAY);
ESP_LOGI(TAG_CONFIG, "[DATA EVT]:");
// char data = (const char) dtmp;
// printf("letter: %s", data);
// int evSize = event.size;
int lastChar = 0;
for (int i = 0; i <= event.size; i++)
{
const char letter = (const char)dtmp[i];
if (dtmp[i] == 10 || dtmp[i] == 0)
{
break;
}
cmd[i] = letter;
lastChar = i;
}
cmd[++lastChar] = '\0';
ESP_LOGE(TAG_CONFIG, "Your command: %s ", cmd);
if (strstr(cmd, set_serial) != NULL)
{
// contains
int lastChar2 = 0;
for (int i = strlen(set_serial) + 1; i < lastChar; i++)
{
int index = i - strlen(set_serial) - 1;
serialNum[index] = cmd[i];
lastChar2 = index;
}
serialNum[++lastChar2] = '\0';
ESP_LOGW(TAG_CONFIG, "setting serial: %s ", serialNum);
int len = strlen(serialNum);
char hex_str[(len * 2) + 1];
// converting ascii string to hex string
string2hexString(serialNum, hex_str);
printf("serialNum: %s\n", serialNum);
printf("hex_str: %s\n", hex_str);
esp_efuse_coding_scheme_t coding_scheme = esp_efuse_get_coding_scheme(EFUSE_BLK3);
write_efuse_fields(serialNum, coding_scheme);
}
This function works perfectly and I can print the serial number as string or as hex:
serialNum: exampleserial123
hex_str: 6578616D706C6573657269616C313233
The next function writes this data to the efuse of the esp:
static void write_efuse_fields(char *serial_num, esp_efuse_coding_scheme_t coding_scheme)
{
// uint8_t unique_id[16] = {0x48, 0x42, 0x30, 0x31, 0x39, 0x39, 0x39, 0x39, 0x30, 0x31, 0x32, 0x33};
ESP_ERROR_CHECK_WITHOUT_ABORT(esp_efuse_write_field_blob(ESP_EFUSE_USER_DATA, &serial_num, 128));
}
when I read the efuse block after running the above code:
ee 17 fd 3f 00 00 00 ff e4 38 fd 3f 0f 00 00 00
Hex to text: îý?ÿä8ý?
If I use the hex output in write_efuse_fields(hex_str, coding_scheme)
I will get:
90 17 fd 3f 00 00 00 ff e4 38 fd 3f 0f 00 00 00
Hex to text: ý?ÿä8ý?
When I do:
uint8_t unique_id[16] = {0x48, 0x42, 0x30, 0x31, 0x39, 0x39, 0x39, 0x39, 0x30, 0x31, 0x32, 0x33};
ESP_ERROR_CHECK_WITHOUT_ABORT(esp_efuse_write_field_blob(ESP_EFUSE_USER_DATA, &unique_id, 128));
I get the expected result.
What is the correct way to convert my char array to a byte like array (similar to unique_id) to get the esp_efuse_write_field_blob to accept it?