Echelon LonTal Stack - Manual (Page 224)

212 Appendix G: Appendix G
Example LonTalk
Stack Applications
LonResgisterUniqueId(&uid);
#endif
sts = LonInit();
if (sts == LonApiNoError)
{
/* This is the main control loop, which runs forever. */
while (!shutdownApp)
{
/* Whenever the ready event is fired, process events by calling
* LonEventPump. The ready event is fired by the myEventReady
* callback.
*/
if (OsalWaitForEvent(eventReadyHandle, OSAL_WAIT_FOREVER) ==
OSALSTS_SUCCESS)
{
LonEventPump();
}
if (sendServicPin)
{
LonSendServicePin();
sendServicPin = FALSE;
}
}
}
else
{
printf(
"Error: LonInit failed with error #%d\n" , sts);
}
LonExit();
appTaskRunning = FALSE;
Event Handler Function
To signal to the main application the occurrence of certain types of events, the
LonTalk API calls specific event handler functions. For the simple voltage
amplifier example application, only one of the API’s event handler functions has
been implemented to provide application-specific behavior.
The FtxlHandlers.c file contains the modified LonNvUpdateOccurred()
function, which is called when the host processor receives a network-variable
update. This function simply calls the myNvUpdateOccurred() function in the
main.c file that provides the application-specific behavior. This functional
separation approach keeps changes to the LonTalk Interface Developer
utility-generated files to a minimum. For a production-level application, you can
place application-specific code wherever your application design requires it.
The myNvUpdateOccurred() function contains a C switch statement, which
contains a single case statement because the VoltActuator functional block
includes only a single input network variable, nviVolt.
The case statement for the nviVolt network variable (specified by the
LonNvIndexNviVolt network variable index) calls the
ProcessNviVoltUpdate() utility function to perform the following tasks:
• Perform range checking for the network variable
• Set the output network variable to double the value of the input network
variable
• Propagate the output network variable to the network