AN197

10

Rev. 0.6

// If we need to make the call again, then decrement the serial index so we can

// accessit the next time through the loop

if (ERROR_MORE_DATA == status)

serialIndex--;

// Otherwise, the call is a success, and we can compare the portString from the

// key to the port string that we want, if they match then retrieve the port

else if (ERROR_SUCCESS == status)

{

if (portString == portKeyString)

{

if (ERROR_SUCCESS == RegQueryValueEx(tmpKey, "Portname", NULL, &valtype,

(unsigned char *)portString, &length))

{

// When we obtain this key, it will be in string format of

// "COMXX" where XX is the port. Simply make the first three

// elements of the string 0, and call the atoi function to obtain

// the number of the port.

portString[0] = '0';

portString[1] = '0';

portString[2] = '0';

portNum = atoi(portString);

}

}

}

// Increment the serial index

serialIndex++;

serKeyString.Format("Enum\\SLABCR\\guid\\%.4d", serialIndex);

// Make sure to close all open keys for cleanup

RegCloseKey(tmpKey);

}

RegCloseKey(HKEY_LOCAL_MACHINE);

// Return the number of the port the device is connected too

return portNum;

}

7.3. Sample Program to Retrieve a CP210x COM Port

Included in the AN197SW.zip is a directory named "CP210xPortNumExample" that contains the source code and

executables for a Visual Studio project that makes use of these functions. In the program, the number of CP210x

devices are found and then for each one a port number is retrieved for it and listed in the edit box. (This program

also makes use of the CP210xManufacturing.DLL to find the VID, PID, and serial number on a device. The use of

this DLL is defined in more detail in "AN144: CP210x Device Customization Guide".)