National Instruments 320682C

Chapter 5 RS-232 Library

Note: The callback function may receive more than one event at a time. When using this

function at higher baud rates, some LWRS_RXCHAR events may be missed. It is

recommended to use LWRS_RECEIVE or LWRS_RXFLAG instead.

Note: Once the LWRS_RECEIVE event occurs, it is not triggered again until the input queue

falls below, and then rises back above, notifyCount bytes.

Example

notifyCount = 50; /* Wait for at least 50 bytes in queue */

eventChar = 13; /* Wait for LF */

eventMask = LWRS_RXFLAG | LWRS_TXEMPTY | LWRS_RECEIVE;

InstallComCallback (comport, eventMask, notifyCount,

eventChar, ComCallback, NULL);

...

/* Callback Function */

void ComCallback(int portNo, int evnetMask, void *data)

{

if (eventMask & LWRS_RXFLAG)

printf("Received specified character\n");

if (eventMask & LWRS_TXEMPTY)

printf("Transmit queue now empty\n");

if (eventMask & LWRS_RECEIVE)

printf("50 or more bytes in input queue\n");

}

Parameters

Input COMPort integer Range 1 through 32.

eventMask integer The events upon which the callback function

is called. See the Parameter Discussion for a

list of valid events. If you want to disable

callbacks, pass 0.

notifyCount integer The minimum number of bytes the input

queue must contain before sending the

LWRS_RECEIVE event to the callback

function.

Valid Range: 0 to Size of Input Queue.

eventCharacter integer Specifies the character or byte value that

triggers the LWRS_RXFLAG event.

Valid Range: 0 to 255.

callbackPtr ComCallbackPtr The name of the user function that processes

the event callback.

callbackData void *A pointer to a user-defined four-byte value

that is passed to the callback function.