'***********************************************************
'**                                                       **
'**              I2C Routines for the BX-24               **
'**       to demonstrate the use of multiple SRF08's      **
'**                                                       **
'**             Copyright 2002 - Devantech Ltd            **
'**     Commercial use of this software is prohibited     **
'**     Private and educational use only is permitted     **
'**                                                       **
'**        Written by Gerald Coe - February 2002          **
'**                                                       **
'***********************************************************

Const	SCL	As Byte = 14		' I2C clock - choose any pins you wish for SCL and SDA
Const	SDA	As Byte = 13		' I2C data

Const	CmdReg As Byte = 0		' SRF08 command register
Const	LdrReg As Byte = 1		' Address of Light Sensor Register in SRF08
Const	RangeReg As Byte = 2	' Address of Range Register in SRF08
Const 	RangeCmd As Byte = 81	' Ranging command - 80 for inches, 81 for cm, 82 for uS

' Note that SRF08's must have been previously set to these addresses
Const	Sonar1 As Byte = &He0	' 1st SRF08 at I2C address 0Xe0
Const	Sonar2 As Byte = &He2	' 2nd SRF08 at I2C address 0Xe2

Dim		I2cAck As Boolean		' Acknowledge flag
	

Sub Main()
Dim Ldr1 As Byte
Dim Range1 As New UnsignedInteger
Dim Ldr2 As Byte
Dim Range2 As New UnsignedInteger

	Call PutPin(SCL, bxOutputHigh)
	Call PutPin(SDA, bxOutputHigh)

Do
' 1st SRF08 Ranger
	Call	I2cByteWrite(Sonar1, CmdReg, RangeCmd)		' Start Ranging in Cm
	Call	Delay(0.07)						' 70mS wait for ranging to complete
	Ldr1 = I2cByteRead(Sonar1, LdrReg)			' Read light sensor
	Range1 = I2cWordRead(Sonar1, RangeReg)		' Read Range Register

' 2nd SRF08 Ranger
	Call	I2cByteWrite(Sonar2, CmdReg, RangeCmd)		' Start Ranging in Cm
	Call	Delay(0.07)						' 70mS wait for ranging to complete
	Ldr2 = I2cByteRead(Sonar2, LdrReg)			' Read light sensor
	Range2 = I2cWordRead(Sonar2, RangeReg)		' Read Range Register

	debug.Print "LDR1 = "; CStr(Ldr1); ", Range1 = ";	CStr(Range1); _
           "     LDR2 = "; CStr(Ldr2); ", Range2 = ";	CStr(Range2)
Loop
End Sub


'--------------------------------------------------------------------------------------------
' I2C subroutines follow
'--------------------------------------------------------------------------------------------

' writes I2cData to I2cReg at I2cAddr
Sub I2cByteWrite(ByVal I2cAddr As Byte, ByVal I2cReg As Byte, ByVal I2cData As Byte)
	Call	I2cStart()
	Call	I2cOutByte(I2cAddr)			' send device address
	Call	I2cOutByte(I2cReg)				' send register address
	Call	I2cOutByte(I2cData)			' send the data
	Call	I2cStop()
End Sub
	

Function I2CByteRead(ByVal I2cAddr As Byte, ByVal I2cReg As Byte) As Byte
	Call	I2cStart()
	Call	I2cOutByte(I2cAddr)			' send device address
	Call	I2cOutByte(I2cReg)				' send register address
	Call	I2cStart()					' repeated start
	I2cAddr = I2cAddr+1
	Call	I2cOutByte(I2cAddr)			' send device address with read set
	I2cAck = False					' setup to send Nak
	I2cByteRead = I2cInByte()			' get data byte with Nak
	Call	I2cStop()
End Function


Function I2CWordRead(ByVal I2cAddr As Byte, ByVal I2cReg As Byte) As UnsignedInteger
	Set I2CWordRead = New UnsignedInteger
	Call	I2cStart()
	Call	I2cOutByte(I2cAddr)			' send device address
	Call	I2cOutByte(I2cReg)				' send register address
	Call	I2cStart()					' repeated start
	I2cAddr = I2cAddr+1
	Call	I2cOutByte(I2cAddr)			' send device address with read set
	I2cAck = True					' setup to send Ack
	I2cWordRead = CuInt(I2cInByte()*256)
	I2cAck = False					' setup to send Nak
	I2cWordRead = I2cWordRead + CuInt(I2cInByte())
	Call	I2cStop()
End Function


Sub I2cOutByte(I2cData As Byte)
	Call	ShiftOut(SDA, SCL, 8, I2cData)		' shift data out
	Call	PutPin(SDA, bxInputTristate)		' turn SDA around
	Call	PutPin(SCL, bxOutputHigh)			' and clock in the ack' bit
	Call	PutPin(SCL, bxOutputLow)
End Sub


Function I2cInByte() As Byte
	I2cInByte = ShiftIn(SDA, SCL, 8)
	If I2cAck=True Then 
		Call	PutPin(SDA, bxOutputLow)
	Else
		Call	PutPin(SDA, bxOutputHigh)
	End If
	Call	PutPin(SCL, bxOutputHigh)			' clock out the ack' bit
	Call	PutPin(SCL, bxOutputLow)
End Function


Sub I2cStart()					' I2C start bit sequence
	Call	PutPin(SDA, bxOutputHigh)
	Call	PutPin(SCL, bxOutputHigh)
	Call	PutPin(SDA, bxOutputLow)
	Call	PutPin(SCL, bxOutputLow)
End Sub


Sub I2cStop()						' I2C stop bit sequence
	Call	PutPin(SDA, bxOutputLow)
	Call	PutPin(SCL, bxOutputHigh)
	Call	PutPin(SDA, bxOutputHigh)
End Sub