How to see what data is being send

Aeroplane123

I have a function

uint16_t Widget::writeFlashPage(uint8_t pageId, uint8_t *data, uint16_t pageSize){

    uint16_t payLoadSize = pageSize + 1;
    uint16_t cmdSize = payLoadSize + 8;

    uint8_t cmd[3000];

    memcpy(cmd, "x", 4);
    cmd[4] =  CMD_SENDING_FIRMWARE_PAGE & 0xFF;
    cmd[5] = (CMD_SENDING_FIRMWARE_PAGE << 8) & 0xFF;
    cmd[6] = (uint8_t)(payLoadSize & 0xFF);
    cmd[7] = (uint8_t)(payLoadSize >>8);
    cmd[8] = pageId;

    memcpy(&cmd[9], data, pageSize);

    cmd[8 + payLoadSize] = calcChecksum(cmd, cmdSize);

    char* cmdChar = reinterpret_cast<char*>(cmd); // this conversion is needed so we can send via serial port!

    bool success = serialPort.write(cmdChar, cmdSize + 1);

How can I see what data is being sent to the serial port via qDebug()?

JonB

@Aeroplane123
That is probably because it has something like x followed by a byte of \0, which it takes as a C string terminator and does not show any further bytes.

To get qDebug() to show what is really there you will need something like:

QByteArray ba(cmd, cmdSize + 1);
qDebug() << ba;
// or
qDebug() << ba.toHex(':');

JonB

@Aeroplane123
Umm, what about qDebug() << cmd;? is that what you mean??

BTW, in your previous thread on this code I told you that

cmd[5] = (CMD_SENDING_FIRMWARE_PAGE << 8) & 0xFF;

is wrong. Shame you have chosen to ignore this?

Aeroplane123

Hi can you explain why it is wrong?

JonB

@Aeroplane123
The code you have will always evaluate to precisely a byte of 0. I doubt that is what you intended!

Your << is the wrong operator. Your code for cmd[7] = (uint8_t)(payLoadSize >>8); does the same thing but correctly uses the >> operator here.

Aeroplane123

@JonB Ah yes I can see that now. Thanks.
Indecently when I use qDebug() cmdChar; the output is just "x" and nothing else. Surely this is not correct?

JonB

@Aeroplane123
That is probably because it has something like x followed by a byte of \0, which it takes as a C string terminator and does not show any further bytes.

To get qDebug() to show what is really there you will need something like:

QByteArray ba(cmd, cmdSize + 1);
qDebug() << ba;
// or
qDebug() << ba.toHex(':');