Function writeControl

src/microham.c:653–709

Write a control string to the microHam device

// Write a control string to the microHam device
//
static void writeControl(const unsigned char *data, int len)
{
    int i;
    unsigned char seq[8];

    DEBUG("%10d:WriteControl:", TIME);

    for (i = 0; i < len; i++) { DEBUG(" %02x", data[i]); }

    DEBUG(".\n");
    // Control data is in the second frame of a sequence,
    // So send a no-op first. Include statusbyte in first frame.
    // First and last byte of the control message is NOT marked "valid"
    getlock();

    for (i = 0; i < len; i++)
    {
        int ret;

        // encode statusbyte in first frame
        seq[0] = 0x08;
        seq[1] = 0x80;
        seq[2] = 0x80;
        seq[3] = 0x80 | statusbyte;
        seq[4] = 0x48; // marked valid
        seq[5] = 0x80;
        seq[6] = 0x80;
        seq[7] = 0x80 | data[i];

        if (statusbyte & 0x80)
        {
            seq[0] |= 1;
        }

        if (i == 0 || i == len - 1)
        {
            seq[4] = 0x40; // un-mark valid
        }

        if (data[i] & 0x80)
        {
            seq[4] |= 0x01;
        }

        if ((ret = write(uh_device_fd, seq, 8)) < 8)
        {
            MYERROR("WriteControl failed, ret=%d\n", ret);

            if (ret < 0)
            {
                perror("WriteControlError:");
            }
        }
    }

    freelock();
}