I am trying to write an app in C to communication with a device through a COM port.
I am able to send data using Docklight (hyper terminal like program) with the following settings and I can verify that I am receiving it through Itronix LogicPort Logic Analyzer. Baud rate:9600 Parity:None Byte Size:8 Stop bits:1
I am having 2 problems with my C program: 1) sometimes CreateFile returns INVALID_HANDLE_VALUE and the other problem I can't seem to get by is that GetCommState() SetCommState() SetCommTimeouts() always return ERROR_INVALID_PARAMETER 87 (0x57)
Since I couldn't get past this problem, I tried a program in C# and that works just fine, but my program must be in C to communicate with the rest of my code. This program also communicates with other programs in C through sockets.
in Device Manager the device I want to talk to is listed as COM6 under Ports(COM & LPT)
any help would be appreciated!
Below is the code for both programs:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO.Ports;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
byte[] TxBuffer = new byte[20];
SerialPort CommPort = new SerialPort("COM6", 9600, Parity.None, 8, StopBits.One);
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
CommPort.Open();
TxBuffer[0] = (byte)'|';
TxBuffer[1] = 0;
TxBuffer[2] = 0;
TxBuffer[3] = 0;
TxBuffer[4] = 1;
TxBuffer[5] = 100;
TxBuffer[6] = 1;
TxBuffer[7] = 6;
TxBuffer[8] = (byte)'|';
TxBuffer[9] = 1;
}
private void button1_Click(object sender, EventArgs e)
{
CommPort.Write(TxBuffer, 0, 10);
}
}
}
and the C code is:
somewhere
struct serial_dev {
HANDLE hSerial;
};
struct serial_dev sdev; //global
//somewhere in main
if (init_serial(&sdev, com_file) == -1)
return -1;
write_ser(&sdev, buffer, buf_size);
close_serial(&sdev);
// in serial.c
int init_serial(struct serial_dev *sdev, char *port_name)
{
DCB dcbSerialParams;
COMMTIMEOUTS timeouts;
int error = 0;
memset(&dcbSerialParams, 0, sizeof(dcbSerialParams));
memset(&timeouts, 0, sizeof(timeouts));
sdev->hSerial = CreateFile("COM6", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
if (sdev->hSerial == INVALID_HANDLE_VALUE)
{
error = GetLastError();
close_serial(sdev);
fprintf(stderr, "error: could not open serial port (error:%d)\n", error);
return -1;
}
memset(&dcbSerialParams, 0, sizeof(dcbSerialParams));
dcbSerialParams.DCBlength = sizeof(dcbSerialParams);
if (!GetCommState(sdev->hSerial, &dcbSerialParams))
{
close_serial(sdev);
error = GetLastError();
fprintf(stderr, "error: could not get serial port state (%d)\n", error);
return -1;
}
dcbSerialParams.BaudRate = CBR_9600;
dcbSerialParams.ByteSize = 8;
dcbSerialParams.StopBits = ONESTOPBIT;
dcbSerialParams.Parity = NOPARITY;
if (!SetCommState(sdev->hSerial, &dcbSerialParams))
{
close_serial(sdev);
error = GetLastError();
fprintf(stderr, "error: could not set serial port state (%d)\n", error);
return -1;
}
timeouts.ReadIntervalTimeout = 50;
timeouts.ReadTotalTimeoutConstant = 200;
timeouts.ReadTotalTimeoutMultiplier = 10;
timeouts.WriteTotalTimeoutConstant = 50;
timeouts.WriteTotalTimeoutMultiplier = 10;
if (!SetCommTimeouts(sdev->hSerial, &timeouts))
{
close_serial(sdev);
error = GetLastError();
fprintf(stderr, "error: could not set serial port timeouts (%d)\n", error);
return -1;
}
return 0;
}
void close_serial(struct serial_dev *sdev)
{
CloseHandle(sdev->hSerial);
}
int write_ser(struct serial_dev *sdev, void *buf, size_t len)
{
DWORD written;
BOOL success;
success = WriteFile(sdev->hSerial, buf, len, &written, NULL);
if(!success || written == 0)
{
printf("error writing to serial\n");
return -1;
}
printf("writing to serial OK!\n");
return written;
}