onewire.c

myTemp is used to connect PalmOS PDAs to Dallas Microlan(tm) Devices. It currently supports DS1820

/*
  myTemp is used to connect PalmOS PDAs to Dallas Microlan(tm) Devices
  It currently supports DS1820/DS18S20 Digital Thermometers
  Copyright (C) 2000 Christof Klaiber

  This program is free software; you can redistribute it and/or modify it under
  the terms of the GNU General Public License as published by the Free Software
  Foundation; either version 2 of the License, or any later version.

  This program is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
  PARTICULAR PURPOSE.  See the GNU General Public License for more details.

  You should have received a copy of the GNU General Public License along with
  this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  Place, Suite 330, Boston, MA  02111-1307  USA


  Christof Klaiber <[e-mail]>
  Lachnerstr. 22
  76131 Karlsruhe
  Germany
*/

#include <PalmOS.h>
#include <SerialMgrOld.h>

#include "onewire.h"

/*
	local functions
*/
Err	OWTouchBits(UInt16, UInt8, UInt8*);
Err OWTouchBit(UInt16, UInt8*);

Err OWTouchReset(UInt16 serialRefNum, UInt8* devicePresent) {
	SerSettingsType	term;
	Err	err;
	UInt8	serBuf;
	Int32	recTimeout = ((SysTicksPerSecond() / kRecTimeoutScale) == 0) ? 1 : (SysTicksPerSecond() / kRecTimeoutScale);

/*
	default: no device present
*/
	*devicePresent = 0;
	SerReceiveFlush(serialRefNum, 0);
	err = SerSendFlush(serialRefNum);
	if (err)
	{
		return err;
	}
	
/* 
	Change Serial Settings to 9600 Baud
	Reset Pulse needs to be that long 
*/
	term.baudRate = 9600;
	term.flags = serDefaultSettings;
	err = SerSetSettings(serialRefNum, &term);
	if (err)
	{
		return err;
	}
	
/* 
	Send the Reset Pulse 
*/
	serBuf = 0xf0;
/*
	returns the number of bytes transmitted, discarded
*/
	SerSend(serialRefNum, &serBuf, 1, &err);
	if (err)
	{
		return err;
	}

	err = SerSendWait(serialRefNum, -1);
	if (err)
	{
		return err;
	}		
	
/*
	wait for an possible answer to detect devices on the bus
	
	we get a serErrTimeOut if there is nothing attached to the bus
*/	
	err = SerReceiveWait(serialRefNum, 1, recTimeout);
	if ((err != serErrTimeOut) && (err != 0))
	{
		return err;
	}
	
/*
	Get the answer if any
	returned bytes are discarded
	
	we get a serErrTimeOut if there is nothing attached to the bus
*/	
	if (!err)
	{
		SerReceive(serialRefNum, &serBuf, 1, 0, &err);
		if ((err != serErrTimeOut) && (err !=0))
		{
			return err;
		}

		if (serBuf != 0xf0) 
		{
			*devicePresent = 1;
		}
	}

/* 
	reinitialize the Port 
*/
	term.baudRate = 115200;
	term.flags = serDefaultSettings;
	err = SerSetSettings(serialRefNum, &term);
	if (err)
	{
		return err;
	}

/*
	0 returned
*/
	return err;
}


Err OWTouchByte(UInt16 serialRefNum, UInt8* character)
{
	return OWTouchBits(serialRefNum, 8, character);
}

/*
	Name:		OWTouchBits
	Purpose:	Send/Receive a bit to/from 1-wire Devices
	Input:		UInt16	serialRefNum	reference to the serial library
				UInt8*	<->character	character to send, returns character received
	Result:		Err	error
	Name: Christof Klaiber <[e-mail]>
	Versions:	25.01.2001	First working release
				06.12.2003	adaption for version 4
				09.12.2003	code cleanups
				11.12.2003	error handling
				This function is taken from digitemp-1.3/onewire.c by Brian C. Lane <[e-mail]>
*/
Err OWTouchBits(UInt16 serialRefNum, UInt8 nbits, UInt8* character) {
	UInt8	sendbit;
	UInt8 	mask = 0x01;
	UInt8	outChar = *character;
	UInt8 	inch = 0;
	UInt8 	serBuf;
	UInt16	bit;
	Err		err;
	UInt32	numBytes;
	Int32	recTimeout = ((SysTicksPerSecond() / kRecTimeoutScale) == 0) ? 1 : (SysTicksPerSecond() / kRecTimeoutScale);
	
	
	*character = 0;
/* 
	Flush Input and Output Queue 
*/
	SerReceiveFlush(serialRefNum, 0);
	err = SerSendFlush(serialRefNum);
	if (err)
	{
		return err;
	}
	
	/* Initialize the Mask to get the Bits one by one */
	mask = 0x01;
	/* Result of this Function */
	inch = 0;
	
	/* Iterrate through the Bits to send */
	for (bit = 0; bit < nbits; bit++) {
		sendbit = (outChar & mask) ? 0xff : 0x00;
		inch >>= 1;
/* 
	Send the Bit 
*/
		numBytes = SerSend(serialRefNum, &sendbit, 1, &err);
		if (err)
		{
			return err;
		}
		
/* 
	Get Output from the Queue if there is one 
*/
		err = SerReceiveWait(serialRefNum, 1, recTimeout);
		if ((err != serErrTimeOut) && (err != 0))
		{
			return err;
		}
		if (!err)
		{
			numBytes = SerReceive(serialRefNum, &serBuf, 1, 0, &err);
			if (err)
			{
				return err;
			}
			inch |= (serBuf & 0x01)? 0x80:0x00;
		}
		mask <<= 1;
	}

	*character = inch;
	return err;
}