Mbed DMA serial receive unknown length of data

mbed_dma_serial_unknown_length.cpp

#include "mbed.h"

const uint32_t baud = 9600;

uint8_t eQueue_buffer[3 * EVENTS_EVENT_SIZE];
EventQueue eQueue(3 * EVENTS_EVENT_SIZE, eQueue_buffer);
LowPowerTimeout rs232Timeout;

Serial rs232(TX_pin, RX_pin, baud);

uint8_t  rs232_buffer[256] = {0};  // make sure it fits your data
uint16_t rs232_buffer_offset = 0;
uint8_t  rs232_char = 0;

constexpr const uint16_t char_timeout = (8 + 4 + 1 + 1) * 1000000 /
                                        baud; // 1.5 char (8 + 4 bits) + 1 bit start + 1 bit stop

void rs232SerialCb(int e);

void rs232Attach() {
    rs232.read(&rs232_char, 1, event_callback_t(rs232SerialCb), -1);
}

void rs232DoneCb() {
    printf("data[%u]: ", rs232_buffer_offset);

    for (int i = 0; i < rs232_buffer_offset; ++i) {
        printf("%02X ", rs232_buffer[i]);
    }

    printf("\n");

    rs232_buffer_offset = 0;
}

void rs232SerialCb(int e) {  // ISR
    if (rs232_buffer_offset < sizeof(rs232_buffer)) {
        rs232_buffer[rs232_buffer_offset++] = rs232_char;

    } else {
        rs232_buffer_offset = 0;  // prevent buffer overflow
    }

    rs232Timeout.detach();
    rs232Timeout.attach_us(eQueue.event(rs232DoneCb), char_timeout);
    eQueue.call(rs232Attach);
}

int main() {
    Thread eQueueThread;
    eQueueThread.start(callback(&eQueue, &EventQueue::dispatch_forever));

    rs232.set_blocking(false);
    rs232Attach();

    while (1) {
        ThisThread::sleep_for(osWaitForever);
    }
}