'===========================================================
'
'	Dallas 1-Wire Interface
'
'	Copyright 2000 by Jon Hylands
'	jon@huv.com  http://www.huv.com
'
'===========================================================

'-----------------------------------------------------------
'	DallasBaseROMAddress is the starting address of
'	where the ROM ids are stored in the BasicX-24 EEPROM
'	as the result of doing a SearchROM.
'
'	The structure one byte for the total number of devices,
'	followed by 8 bytes for each device's ROM id.

public const DallasBaseROMAddress as Long = &h7200

'-----------------------------------------------------------

private const DallasReadROM as Byte = &h33
private const DallasMatchROM as Byte = &h55
private const DallasSkipROM as Byte = &hCC
private const DallasSearchROM as Byte = &hF0

private lastROMArray (1 to 8) as Byte

'-----------------------------------------------------------
'	Reset_1Wire
'
'	Reset the 1-wire bus by sending a 500 usec low pulse.
'	Return true if any devices respond, false if there
'	are no devices on the bus.

public Function Reset_1Wire (ByVal busPin as Byte) as Boolean

	dim index as Integer
	dim busTransitions as Long
	dim pinValues (1 to 10) as Byte

	' It is important for timing reasons that this function
	' not be pre-empted...
	call LockTask
	call PutPin (busPin, bxInputTristate)
	call PutPin (busPin, bxOutputLow)

	' Delay for ~500 usec - fake it with PulseOut on pin 0...
	call PulseOut (0, 0.0005, 0)

	' Now let the pullup resistor do its thing...
	Call PutPin (busPin, bxInputTristate)

	' Look for the presence pulse over a 300 usec period
	busTransitions = CountTransitions (busPin, 0.0003)

	call UnlockTask
	Reset_1Wire = (busTransitions > 0)

End Function

'-----------------------------------------------------------
'	ReadROM_1Wire
'
'	Read the 64-bit ROM value of the single device on
'	the bus. If there is more than one device on the bus,
'	this routine will end up giving a bad ROM id.

public Sub ReadROM_1Wire (ByVal busPin as Byte, ByRef romArray() as Byte)

	dim index as Integer

	if not Reset_1Wire (busPin) then
		Exit Sub
	end if

	call PutByte_1Wire (busPin, DallasReadROM)
	for index = 1 to 8
		romArray (index) = InByte_1Wire (busPin)
	next

End Sub

'-----------------------------------------------------------
'	MatchROM_1Wire
'
'	Select the device on the bus that has a ROM id matching
'	the contents of romArray.

public Sub MatchROM_1Wire (ByVal busPin as Byte, ByRef romArray() as Byte)

	dim index as Integer

	if not Reset_1Wire (busPin) then
		Exit Sub
	end if

	call PutByte_1Wire (busPin, DallasMatchROM)
	for index = 1 to 8
		call PutByte_1Wire (busPin, romArray (index))
	next

End Sub

'-----------------------------------------------------------
'	SkipROM_1Wire
'
'	Skip the whole device select thing -- this only works
'	in general if there is only device on the bus

public Sub SkipROM_1Wire (ByVal busPin as Byte)

	if not Reset_1Wire (busPin) then
		Exit Sub
	end if

	call PutByte_1Wire (busPin, DallasSkipROM)

End Sub

'-----------------------------------------------------------
'	SearchROM_1Wire
'
'	Find the 64 bit ROM id of each device connected
'	to the bus.
'
'	Store the ROM ids in EEPROM memory, starting at the address
'	specified by the global constant DallasBaseROMAddress.
'
'	Return the number of devices that were found.

public Function SearchROM_1Wire (ByVal busPin as Byte) as Byte

	dim lastConflict as Byte, deviceIndex as Byte
	dim index as Integer

	lastConflict = 0
	deviceIndex = 0
	for index = 1 to 8
		lastROMArray (index) = 0
	next

	if not Reset_1Wire (busPin) then
		SearchROM_1Wire = 0
		Exit Function
	end if

	' Loop once per device
	do
		lastConflict = HandleSearch_1Wire (busPin, lastConflict, deviceIndex)
		deviceIndex = deviceIndex + 1
	loop until lastConflict = 0

	' Finally, save the device count as the first byte in our
	' EEPROM storage area
	call PersistentPoke (deviceIndex, CuInt (DallasBaseROMAddress))
	SearchROM_1Wire = deviceIndex

End Function

'-----------------------------------------------------------
'	HandleSearch_1Wire
'
'	This is the actual search working routine

private Function HandleSearch_1Wire (ByVal busPin as Byte, _
	ByVal startIndex as Byte, _
	ByVal deviceIndex as Byte) as Byte

	dim bitIndex as Byte, conflictIndex as Byte, value as Byte
	dim bitValue as Byte
	dim romArray (1 to 8) as Byte

	HandleSearch_1Wire = 0
	if not Reset_1Wire (busPin) then
		Exit Function
	end if

	bitIndex = 0
	conflictIndex = 0
	call PutByte_1Wire (busPin, DallasSearchROM)

	' Blast through the last rom, up to the point where we had the conflict
	if deviceIndex > 0 then
		do while bitIndex < startIndex
			value = In2Bits_1Wire (busPin)
			bitValue = GetBit (lastROMArray, bitIndex)
			call Put1Wire (busPin, bitValue)
			call PutBit (romArray, bitIndex, bitValue)
			bitIndex = bitIndex + 1
		loop

		' Okay, now we're there. This time select the ROM with bit one
		value = In2Bits_1Wire (busPin)
		call Put1Wire (busPin, 1)
		call PutBit (romArray, bitIndex, 1)
		bitIndex = bitIndex + 1
	end if

	' Now loop through the rest of the 64 bits, watching for conflicts
	do
		select case In2Bits_1Wire (busPin)
			' case 00 -- devices with both bits, always select 0
			case bx00000000
				conflictIndex = bitIndex
				call PutBit (romArray, bitIndex, 0)
			' case 01 -- all devices have one bit in this position
			case bx00000001
				call PutBit (romArray, bitIndex, 1)
			' case 10 -- all devices have zero bit in this position
			case bx00000010
				call PutBit (romArray, bitIndex, 0)
			' case 11 -- all devices have deselected themselves
			case bx00000011
				Exit Function
		end select
		call Put1Wire (busPin, GetBit (romArray, bitIndex))
		bitIndex = bitIndex + 1
	loop until bitIndex = 64

	' Copy the ROM id to EEPROM, and then save it as the last accessed one
	call PutROMid_1Wire (deviceIndex, romArray)
	call BlockMove (8, MemAddress (romArray), MemAddress (lastROMArray))

	HandleSearch_1Wire = conflictIndex

End Function

'-----------------------------------------------------------
'	PutROMid_1Wire
'
'	Copy the ROM id from the given RAM array to the
'	location in EEPROM indexed by deviceIndex.

public Sub PutROMid_1Wire (ByVal deviceIndex as Byte, ByRef romArray() as Byte)

	call PutEEPROM (DallasBaseROMAddress + 1 + CLng (deviceIndex * 8), romArray, 8)

End Sub

'-----------------------------------------------------------
'	GetROMid_1Wire
'
'	Copy the ROM id indexed by deviceIndex from EEPROM
'	to the given RAM array.

public Sub GetROMid_1Wire (ByVal deviceIndex as Byte, ByRef romArray() as Byte)

	call GetEEPROM (DallasBaseROMAddress + 1 + CLng (deviceIndex * 8), romArray, 8)

End Sub

'-----------------------------------------------------------
'	GetDeviceCount_1Wire
'
'	Return the number of devices found by the last
'	invocation of SearchROM.

public Function GetDeviceCount_1Wire () as Byte

	GetDeviceCount_1Wire = PersistentPeek (CuInt (DallasBaseROMAddress))

End Function

'-----------------------------------------------------------
'	InByte_1Wire
'
'	Pull a byte off the bus from the selected device.

public Function InByte_1Wire (ByVal busPin as Byte) as Byte

	dim index as Byte
	dim inputByte as Byte

	for index = 0 to 7
		call PutBit (inputByte, index, Get1Wire (busPin))
	next

	InByte_1Wire = inputByte

End Function

'-----------------------------------------------------------
'	In2Bits_1Wire
'
'	Pull two bits off the bus from the selected device.

private Function In2Bits_1Wire (ByVal busPin as Byte) as Byte

	In2Bits_1Wire = 0
	call PutBit (In2Bits_1Wire, 0, Get1Wire (busPin))
	call PutBit (In2Bits_1Wire, 1, Get1Wire (busPin))

End Function

'-----------------------------------------------------------
'	PutByte_1Wire
'
'	Output a byte to the selected device on the bus.

public  Sub PutByte_1Wire (ByVal busPin as Byte, ByVal outputByte as Byte)

	dim index as Byte

	for index = 0 to 7
		call Put1Wire (busPin, GetBit (outputByte, index))
	next

End Sub