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void LIN_driver_start_frame(uint8_t pid)
{
    uint32_t baudrate;
    uint8_t master_tx_buf[2];
    master_tx_buf[0] = 0x55; // sync byte
    master_tx_buf[1] = pid;

    uint8_t dummy = 0;

    uart_flush_input(lin_uart_num);    // since we are the master, clear out rx buff before starting a frame
    xQueueReset(lin_uart_event_queue); // clear the q for slave rx uart breaks
    /* Send break character */
    // this method sucks b/c it must send a dummy char before the break
    // Note: if use this, then +1 to LIN_IN_HEADER_SIZE for dummy byte.
    //uart_write_bytes_with_break(lin_uart_num, (char *)&dummy, 1, LIN_BREAK_LEN);

    // this method really sucks because of a blocking delay!
    //uart_set_line_inverse(param_ptr_config->uart_port_num, UART_INVERSE_TXD);
    //ets_delay_us(677);
    //uart_set_line_inverse(param_ptr_config->uart_port_num, UART_INVERSE_DISABLE);

    //uart_hal_tx_break(&(uart_context[uart_num].hal), 0); - not available in IDF 3x

    // Temporarily change baudrate to slightly lower and send a 0 byte
    // to get the right baudrate, we want 9 bits (1 start + 8 data) to take the time of 13 bits (one break)
    uart_get_baudrate(lin_uart_num, &baudrate);
#define LIN_BREAK_BAUDRATE(BAUD) ((BAUD * 9) / 13)
    uart_set_baudrate(lin_uart_num, LIN_BREAK_BAUDRATE(baudrate));
    uart_write_bytes(lin_uart_num, (char *)&dummy, 1); // send a zero byte.  This call must be blocking.
    uart_wait_tx_done(lin_uart_num, 2);                // shouldn't be necessary??
    uart_wait_tx_done(lin_uart_num, 2);                // add 2nd uart_wait_tx_done per https://esp32.com/viewtopic.php?p=98456#p98456
    uart_set_baudrate(lin_uart_num, baudrate);         // set baudrate back to normal after break is sent
    // we have to fake a break detect for the slave, since it doesn't detect it with this method.
    uart_event_t event = {.type = UART_BREAK};
    xQueueSend(lin_uart_event_queue, (void *)&event, 0);

    // Now send the sync and PID bytes
    uart_write_bytes(lin_uart_num, (char *)master_tx_buf, sizeof(master_tx_buf));
}