'{$STAMP BS2}

'***********************************************************
'**                                                       **
'**            I2C Routines for the Basic Stamp           **
'**            using the CMPS01 Compass Module            **
'**                                                       **
'**             Copyright 2002 - Devantech Ltd            **
'**     Commercial use of this software is prohibited     **
'**     Private and educational use only is permitted     **
'**                                                       **
'**        Written by Gerald Coe - January 2002           **
'**                                                       **
'**      This Code has been Tested on BS2 and BS2p        **
'**  It should work equally well on the BS2e and BS2sx    **
'**                                                       **
'***********************************************************


SDA		con	8			' I2C data
SCL  		con	9			' I2C clock
SDAin		var	in8
SDAout	var	out8
SDAdir	var	dir8

loop		var	byte			' just a looping counter
I2cBuf	var	byte			' I2c read/write buffer
I2cAddr	var	byte			' Address of I2C device
I2cReg	var	byte			' Register number within I2C device
I2cData	var	word			' Data to read/write
I2cAck	var	bit			' Acknowledge bit
	

Main:
	I2cAddr = $c0			' CMPS01 Compass module address
	I2cReg = 1				' Bearing as 0-255 (BRAD)
	gosub	I2cByteRead
	debug	2,0,0, "Compass Bearing (0-255 BRAD)   ", dec3 I2cData
	I2cReg = 2				' Bearing as 0-359.9 degrees
	gosub	I2cWordRead
	debug	2,0,1, "Compass Bearing (0-359 Degrees ", dec3 I2cData/10

	goto	main


I2cByteWrite:				' writes I2cData.lowbyte to I2cReg at I2cAddr
	gosub	I2cStart
	I2cBuf = I2cAddr	
	gosub	I2cOutByte			' send device address
	I2cBuf = I2cReg	
	gosub	I2cOutByte			' send register number
	I2cBuf = I2cData.lowbyte	
	gosub	I2cOutByte			' send the data
	gosub	I2cStop
	return
	

I2cWordWrite:				' writes I2cData to I2cReg at I2cAddr
	gosub	I2cStart
	I2cBuf = I2cAddr	
	gosub	I2cOutByte			' send device address
	I2cBuf = I2cReg	
	gosub	I2cOutByte			' send register number
	I2cBuf = I2cData.highbyte
	gosub	I2cOutByte			' send the data - high byte
	I2cBuf = I2cData.lowbyte
	gosub	I2cOutByte			' send the data - low byte
	gosub	I2cStop
	return
	

I2CByteRead:
	gosub	I2cStart
	I2cBuf = I2cAddr	
	gosub	I2cOutByte			' send device address
	I2cBuf = I2cReg	
	gosub	I2cOutByte			' send register number
	gosub	I2cStart			' repeated start
	I2cBuf = I2cAddr | 1	
	gosub	I2cOutByte			' send device address (with read set)
	I2cAck = 0				' send Nak
	gosub	I2cInByte
	I2cData.lowbyte = I2cBuf	' read the data
	I2cData.highbyte = 0
	gosub	I2cStop
	return


I2CWordRead:
	gosub	I2cStart
	I2cBuf = I2cAddr	
	gosub	I2cOutByte			' send device address
	I2cBuf = I2cReg	
	gosub	I2cOutByte			' send register number
	gosub	I2cStart			' repeated start
	I2cBuf = I2cAddr | 1	
	I2cAck = 1				' send Ack
	gosub	I2cOutByte			' send device address (with read set)
	gosub	I2cInByte
	I2cData.highbyte = I2cBuf	' read the data
	I2cAck = 0				' send Nak
	gosub	I2cInByte
	I2cData.lowbyte = I2cBuf
	gosub	I2cStop
	return


I2cOutByte:
	shiftout SDA, SCL, MSBFIRST, [I2cBuf]
	input	SDA
	high	SCL					' clock in the ack' bit
	low	SCL
	return

 
I2cInByte:
	shiftin SDA, SCL, MSBPRE, [I2cBuf]
	SDAout = 0
	SDAdir = I2cAck
	high	SCL					' clock out the ack' bit
	low 	SCL
	input	SDA
	return


I2cStart						' I2C start bit sequence
	high	SDA
	high	SCL
	low	SDA
	low	SCL
	return


I2cStop:						' I2C stop bit sequence
	low	SDA
	high	SCL
	high	SDA
	return