Serial port communication read function cannot read full response - c++

Question

I am having issues with reading complete return string after sending an "ATZ" command to my OBDII dongle device with an STN1100 chip in it. Here is the return response of sending "ATZ" command on putty:
Here is my COM setting code:
LPCWSTR port = L"COM6";
device = CreateFile(port,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
NULL,
0);
if (device == INVALID_HANDLE_VALUE) {
printf("Failed to open port\n");
printf("error code is %i\n", device);
return false;
}
else
printf("Port is open successfully!\n");
//Settings
/*Timeout*/
COMMTIMEOUTS timeout;
timeout.ReadIntervalTimeout = 1;
timeout.ReadTotalTimeoutConstant = 1;
timeout.ReadTotalTimeoutMultiplier = 1;
timeout.WriteTotalTimeoutConstant = 1;
timeout.WriteTotalTimeoutMultiplier = 1;
if (!SetCommTimeouts(serialHandle, &timeout)) {
printf("Error setting the timeout\n");
printf("Error code: %i\n", GetLastError());
}
/**/
DCB serialParams;
serialParams.DCBlength = sizeof(serialParams);
if (!GetCommState(device, &serialParams)) //need this getCommState before setCommState
printf("Error getting current DCB settings\n");
serialParams.BaudRate = CBR_9600;
serialParams.ByteSize = 8;
serialParams.StopBits = ONESTOPBIT;
serialParams.Parity = NOPARITY;
serialParams.fOutX = FALSE;
serialParams.fInX = FALSE;
serialParams.fBinary = TRUE;
serialParams.fNull = TRUE;
serialParams.fRtsControl = RTS_CONTROL_DISABLE;
if (!SetCommState(device, &serialParams)) {
printf("Error setting the DCB\n");
printf("Error code: %i\n", GetLastError());
}
Here is my Write and Read function:
bool Write(HANDLE device) {
bool bErrorFlag = FALSE;
char DataBuffer[] = "ATZ\n";
//char* cmd = DataBuffer;
DWORD dwBytesToWrite = (DWORD)strlen(DataBuffer);
DWORD dwBytesWritten = 0;
bErrorFlag = WriteFile(
device,
DataBuffer,
3,
&dwBytesWritten,
NULL);
if (!bErrorFlag) {
printf("Failed to write to device\n");
printf("Error code: %i\n", GetLastError());
return false;
}
return true;
}
bool Read(HANDLE device) {
char ReadBuffer[256] = { 0 };
int BUFFERSIZE = 256;
DWORD dwBytesRead = 0;
DWORD read;
OVERLAPPED ol = { 0 };
if (!ReadFile(device, ReadBuffer, BUFFERSIZE - 1, &read, 0))
{
printf("Terminal failure: Unable to read from device.\n GetLastError=%08x\n", GetLastError());
CloseHandle(device);
return false;
}
printf("Response is %s\n", ReadBuffer);
return true;
}
I can only receive returned echo command "ATZ" by running the code above, does anyone know what setting I did wrong? It looks like the read function stops reading from the buffer after receiving the first line.