poll1.c

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#include "pioLib.h"

IMPORT DAADIO	daadio;
IMPORT PIO		pio;

void pioPoll (port, msgQId)
	int port;
	MSG_Q_ID msgQId;
	{
	PIO_MSG_Q_DATA 	msgQData;
	UINT8 			currentState;
	UINT8 			lastState = 0;
	UINT8 			changedChannels;
	UINT8 *			pPort;
	UINT8			channelBit;	
	int 			channel;	
	IMPORT int		errno;

	/* Error checking */
	if (pio.initialized == FALSE)
		{
		printf ("pio not initialized\n");
		return;
		}

	/* Fail if not an input port, i.e. if the corresponding bit in the
	   output enable register is on */
	if (*((UINT8 *)daadio.baseAddr + PIO_OUTPUT_ENABLE_OFFSET) & (1 << port))
		{
		printf ("port not an input port\n");
		return;
		}
	
	/* Initialize <pPort> to point to the appropriate port */
	pPort = PIO_PORT_NUM_TO_ADDR (port);

	FOREVER
		{
		taskDelay (PIO_POLL_DELAY);

		/* Get the current state of all the channels in the port. */
		currentState = *pPort;

		/* If the state of the channels did not change, loop back. */
		if (currentState == lastState)
			continue;
		
		/* Identify which channels changed state.  By exclusive or'ing
		   the current with the last state, we have, for each channel
		   in the port, the corresponding bit set in <changedChannels>. */
		changedChannels = currentState ^ lastState;

		/* Check each bit in <changedChannels> to see if that channel
		   changed state.  <channel> keeps track of which channel
		   number we are checking. <channelToCheck> just holds a single
		   set bit corresponding with the channel number we are checking
		   for. */
		for (channel=0; channel<PIO_MAX_CHANNELS_PER_PORT; channel++)
			{

			/* Set a bit in <channelBit> which reflects the channel
			   we are checking. I.e., if channel 0, set bit 0; if 
			   channel 1, set bit 1, and so on. */

			channelBit = 1 << channel;

			/* If the <channelBit> bit is not set in <changedChannels>
			   then this <channel> did not change. Loop back and check
			   the next channel. */

			if ((changedChannels & channelBit) == 0)
				continue;

			/* <channel> changed */

			msgQData.port = port;
			msgQData.channel = channel;
			msgQData.state = (currentState & channelBit) ? ON : OFF;
			msgQData.timeStamp = tickGet();	

			if (msgQSend (msgQId, &msgQData, sizeof (PIO_MSG_Q_DATA),
								NO_WAIT, MSG_PRI_NORMAL) == ERROR)
				{

				/* If failure was because queue is full, just print
					  warning and continue. Any other failure, print
					  message and terminate. */

				if (errno == S_objLib_OBJ_UNAVAILABLE)
					printf ("Msg Queue full: dumping data for port %d, channel %d, status is %s at clock tick %d\n", 
							port, channel, (msgQData.state) ? "ON" : 
							"OFF", msgQData.timeStamp);
				else
					{
					printf ("Msg Queue fatal error: aborting poll task\n");
					return;
					}
				}
			
			}
			/* Update the last state with the current state */
			lastState = currentState;
		}
	}