1WREAD

Action

This statement reads data from the 1wire bus into a variable.

 

 

Syntax

var2 = 1WREAD( [ bytes] )

var2 = 1WREAD( bytes , port , pin)

 

 

Remarks

var2	Reads a byte from the bus and places it into variable var2.   Optional the number of bytes to read can be specified.
Port	The PIN port name like PINB or PIND.
Pin	The pin number of the port. In the range from 0-7. Maybe a numeric constant or variable.

 

 

Multi 1-wire devices on different pins are supported.

To use this you must specify the port pin that is used for the communication.

 

The 1wreset, 1wwrite and 1wread statements will work together when used with the old syntax. And the pin can be configured from the compiler options or with the CONFIG 1WIRE statement.

 

 

The syntax for additional 1-wire devices is :

1WRESET port, pin

1WWRITE var/constant , bytes, port, pin

var = 1WREAD(bytes, port, pin) for reading multiple bytes

 

 

See also

1WWRITE , 1WRESET

 

 

 

Example

'--------------------------------------------------------------------------------
'name : 1wire.bas
'copyright : (c) 1995-2005, MCS Electronics
'purpose : demonstrates 1wreset, 1wwrite and 1wread()
'micro : Mega48
'suited for demo : yes
'commercial addon needed : no
' pull-up of 4K7 required to VCC from Portb.2
' DS2401 serial button connected to Portb.2
'--------------------------------------------------------------------------------
 
$regfile = "m48def.dat"
$crystal = 4000000
 
$hwstack = 32 'default use 32 for the hardware stack
$swstack = 10 'default use 10 for the SW stack
$framesize = 40 'default use 40 for the frame space
 
 
'when only bytes are used, use the following lib for smaller code
$lib "mcsbyte.lib"
 
 
Config 1wire = Portb.0 'use this pin
'On the STK200 jumper B.0 must be inserted
Dim Ar(8) As Byte , A As Byte , I As Byte
 
 
Do
Wait 1
1wreset 'reset the device
Print Err 'print error 1 if error
1wwrite &H33 'read ROM command
For I = 1 To 8
 Ar(i) = 1wread() 'place into array
Next
 
 
'You could also read 8 bytes a time by unremarking the next line
'and by deleting the for next above
'Ar(1) = 1wread(8) 'read 8 bytes
 
 
For I = 1 To 8
 Print Hex(ar(i)); 'print output
Next
Print 'linefeed
Loop
 
 
'NOTE THAT WHEN YOU COMPILE THIS SAMPLE THE CODE WILL RUN TO THIS POINT
'THIS because of the DO LOOP that is never terminated!!!
 
 
'New is the possibility to use more than one 1 wire bus
'The following syntax must be used:
For I = 1 To 8
Ar(i) = 0 'clear array to see that it works
Next
 
 
1wreset Pinb , 2 'use this port and pin for the second device
1wwrite &H33 , 1 , Pinb , 2 'note that now the number of bytes must be specified!
'1wwrite Ar(1) , 5,pinb,2
 
 
'reading is also different
Ar(1) = 1wread(8 , Pinb , 2) 'read 8 bytes from portB on pin 2
 
 
For I = 1 To 8
Print Hex(ar(i));
Next
 
 
'you could create a loop with a variable for the bit number !
For I = 0 To 3 'for pin 0-3
1wreset Pinb , I
1wwrite &H33 , 1 , Pinb , I
Ar(1) = 1wread(8 , Pinb , I)
For A = 1 To 8
 Print Hex(ar(a));
Next
Print
Next
End

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