Error Codes Returned:

If the port address is not returned by the RTRead and RTWrite functions, then the data portion of the returned value indicates the type of error that occurred.

DosOpen returns one of the following values as rc:

0 NO_ERROR
2 ERROR_FILE_NOT_FOUND
3 ERROR_PATH_NOT_FOUND
4 ERROR_TOO_MANY_OPEN_FILES
5 ERROR_ACCESS_DENIED
12 ERROR_INVALID_ACCESS
26 ERROR_NOT_DOS_DISK
32 ERROR_SHARING_VIOLATION
36 ERROR_SHARING_BUFFER_EXCEEDED
82 ERROR_CANNOT_MAKE
87 ERROR_INVALID_PARAMETER
99 ERROR_DEVICE_IN_USE
108 ERROR_DRIVE_LOCKED
110 ERROR_OPEN_FAILED
112 ERROR_DISK_FULL
206 ERROR_FILENAME_EXCED_RANGE
231 ERROR_PIPE_BUSY

DosDevIOCtl returns one of the following values as rc:

0 NO_ERROR
1 ERROR_INVALID_FUNCTION
6 ERROR_INVALID_HANDLE
15 ERROR_INVALID_DRIVE
31 ERROR_GEN_FAILURE
87 ERROR_INVALID_PARAMETER
111 ERROR_BUFFER_OVERFLOW
115 ERROR_PROTECTION_VIOLATION
117 ERROR_INVALID_CATEGORY
119 ERROR_BAD_DRIVER_LEVEL
163 ERROR_UNCERTAIN_MEDIA
165 ERROR_MONITORS_NOT_SUPPORTED

Note: If you get an error 10 - TESTCFG.SYS could not be opened, then TESTCFG.SYS is not on your system.

If any of the API calls do not work and return errors, then most likely your radio card I/O setting conflicts with another adapter in your system. If you have a network card at 300 hex and your radio card is set to 30C hex, you will not be able to access the radio card as TESTCFG.SYS prevents that. Set the radio card to 20C hex in this case.