A Virtual Com Port Driver for USB to COM converter

Introduction

Install

Method one:

Method two:

Access Device

• Using Windows  API

• Block mode read write.comtst.c
• Monitoring event.comevent.c
• Custom TimeOut setup,a read operation can complete immediately after reading whatever characters are available in the input buffer and block when it is empty.

CommTimeOuts.ReadIntervalTimeout = 3;
CommTimeOuts.ReadTotalTimeoutMultiplier = 0;
CommTimeOuts.ReadTotalTimeoutConstant = 0;
CommTimeOuts.WriteTotalTimeoutMultiplier = 0;
CommTimeOuts.WriteTotalTimeoutConstant = 0;
bRc = SetCommTimeouts(hCommPort, &CommTimeOuts);

• Using MSComm In MFC

1. VC6.0 Project--->Add to Project--->Components and Controls--->Registered ActiveX Controls,Select Components: Microsoft Communications Control. CMSComm class is added.(related file mscomm.h mscomm.cpp ).
2. ......Detailhttp://www.gjwtech.com/scomm/scmfcprogramfujie.htm



• Using USB HID Class Interface

1. Open Device  BOOL bOpenHidDevice(HANDLE *HidDevHandle, USHORT vid, USHORT pid)
2. Setup Baud Rate,Parity and Stop Bits

outbuffer[0] = 0; /* report ID is not used */
*(unsigned int *)&outbuffer[1] = 19200; /* BaudRate */
/*Configuration Byte
7 	6	5		4		3		2	1	0
Reset	0 	Parity Type	Parity Enable	Stop Bits	0	Data Bits
*/
outbuffer[5] = 0x03; /* Data Bits 8, Parity null, Stop Bits 1*/
bResult = HidD_SetFeature(HidDevHandle, outbuffer, Capabilities.FeatureReportByteLength);
if(bResult)
{
}else
	printf("HidD_SetFeature failed %d\n",GetLastError());

3. Read Write

outbuffer[0] = 0; /* report ID is not used*/
outbuffer[1] = 7; /* data len */
for(int i=0; i < 7; i++)
	outbuffer[2+i] = 'a'+i;
bResult = WriteFile(HidDevHandle,
			&outbuffer[0],
    			Capabilities.OutputReportByteLength,
    			&numBytesReturned,
    			NULL);
inbuffer[0] = 0; /* report ID is not used*/
bResult = ReadFile(HidDevHandle,
			&inbuffer[0],
			Capabilities.InputReportByteLength,
			&numBytesReturned,
			NULL);
if(bResult)
{
	//dump data
    	printf("len = %d\n",inbuffer[1]);
    	for(int i=0; i < inbuffer[1]; i++)
    		printf("%c ",inbuffer[i+2]);
}

How does the driver work?

Using the USB-HID->COM Converter on Linux

• Using cypress_m8.ko USB to Serial Driver (kernel >= 2.6)

1. Pluging in the device, if the driver can't auto loaded, execute "modprobe cypress_m8".
2. You can access /dev/ttyUSB? like /dev/ttyUSB? now.

• Using libusb

testlibusb.c

• Using hiddev

todo.

Reference:

• Different ways of handling IRPs
• Proper Completion -- Resubmitting IRPs from within a Completion Routine
• Using the HID class eases the job of writing USB device drivers
• http://www.lvr.com/hidpage.htm
• http://www.gjwtech.com/serialcomm.htm