CONFIG TWI

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</source><br/>{{Languages}}
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</source>
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= <span style="font-size: 19px; font-weight: bold;">XMEGA SAMPLE</span> =
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<source lang="bascomavr">
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'----------------------------------------------------------------
 +
' (c) 1995-2013, MCS
 +
' xm128-TWI.bas
 +
' This sample demonstrates the Xmega128A1 TWI
 +
'-----------------------------------------------------------------
 +
 +
$regfile = "xm128a1def.dat"
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$crystal = 32000000
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$hwstack = 64
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$swstack = 40
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$framesize = 40
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 +
 +
Dim S As String * 20
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 +
'first enable the osc of your choice
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Config Osc = Enabled , 32mhzosc = Enabled
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 +
'configure the systemclock
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Config Sysclock = 32mhz , Prescalea = 1 , Prescalebc = 1_1
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Dim N As String * 16 , B As Byte
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Config Com1 = 19200 , Mode = Asynchroneous , Parity = None , Stopbits = 1 , Databits = 8
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Config Input1 = Cr , Echo = Crlf ' CR is used for input, we echo back CR and LF
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Open "COM1:" For Binary As #1
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' ^^^^ change from COM1-COM8
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Print #1 , "Xmega revision:" ; Mcu_revid ' make sure it is 7 or higher !!! lower revs have many flaws
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Const Usechannel = 1
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 +
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Dim B1 As Byte , B2 As Byte
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Dim W As Word At B1 Overlay
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Open "twic" For Binary As #4 ' or use TWID,TWIE oR TWIF
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Config Twic = 100000 'CONFIG TWI will ENABLE the TWI master interface
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'you can also use TWIC, TWID, TWIE of TWIF
 +
'!!!!!!!!!!! WITHOUT a channel identifier, TWIC will be used !!!!!!!!!!!!!!
 +
 +
#if Usechannel = 1
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I2cinit #4
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#else
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I2cinit
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#endif
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Do
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I2cstart 'since not # is used, TWIC will be used
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Waitms 20
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I2cwbyte &H70 ' slave address write
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Waitms 20
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I2cwbyte &B10101010 ' write command
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Waitms 20
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I2cwbyte 2
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Waitms 20
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I2cstop
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Print "Error : " ; Err ' show error status
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'waitms 50
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Print "start"
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I2cstart
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Print "Error : " ; Err ' show error
 +
I2cwbyte &H71
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Print "Error : " ; Err ' show error
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I2crbyte B1 , Ack
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Print "Error : " ; Err ' show error
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I2crbyte B2 , Nack
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Print "Error : " ; Err ' show error
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I2cstop
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Print "received A/D : " ; W ; "-" ; B1 ; "-" ; B2
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Waitms 500 'wait a bit
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Loop
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Dim J As Byte , C As Byte , K As Byte
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Dim Twi_start As Byte ' you MUST dim this variable since it is used by the lib
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 +
'determine if we have an i2c slave on the bus
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For J = 0 To 200 Step 2
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Print J
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#if Usechannel = 1
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I2cstart #4
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#else
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I2cstart
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#endif
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I2cwbyte J
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If Err = 0 Then ' no errors
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Print "FOUND : " ; Hex(j)
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'write some value to the pcf8574A
 +
#if Usechannel = 1
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I2cwbyte &B1100_0101 , #4
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#else
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I2cwbyte &B1100_0101
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#endif
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Print Err
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Exit For
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End If
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#if Usechannel = 1
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I2cstop #4
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#else
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I2cstop
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#endif
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Next
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#if Usechannel = 1
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I2cstop #4
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#else
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I2cstop
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#endif
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#if Usechannel = 1
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I2cstart #4
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I2cwbyte &H71 , #4 'read address
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I2crbyte J , Ack , #4
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Print Bin(j) ; " err:" ; Err
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I2crbyte J , Ack , #4
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Print Bin(j) ; " err:" ; Err
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I2crbyte J , Nack , #4
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Print Bin(j) ; " err:" ; Err
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I2cstop #4
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#else
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I2cstart
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I2cwbyte &H71 'read address
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I2crbyte J , Ack
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Print Bin(j) ; " err:" ; Err
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I2crbyte J , Ack
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Print Bin(j) ; " err:" ; Err
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I2crbyte J , Nack
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Print Bin(j) ; " err:" ; Err
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I2cstop
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#endif
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'try a transaction
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#if Usechannel = 1
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I2csend &H70 , 255 , #4 ' all 1
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Waitms 1000
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I2csend &H70 , 0 , #4 'all 0
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#else
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I2csend &H70 , 255
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Waitms 1000
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I2csend &H70 , 0
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#endif
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Print Err
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'read transaction
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Dim Var As Byte
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Var = &B11111111
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#if Usechannel = 1
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I2creceive &H70 , Var , 1 , 1 , #4 ' send and receive
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Print Bin(var) ; "-" ; Err
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I2creceive &H70 , Var , 0 , 1 , #4 ' just receive
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Print Bin(var) ; "-" ; Err
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#else
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I2creceive &H70 , Var , 1 , 1 ' send and receive
 +
Print Bin(var) ; "-" ; Err
 +
I2creceive &H70 , Var , 0 , 1 ' just receive
 +
Print Bin(var) ; "-" ; Err
 +
#endif
 +
 +
End
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</source>
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 +
{{Languages}}
  
 
[[Category:BASCOM Language Reference]]
 
[[Category:BASCOM Language Reference]]

Revision as of 12:51, 24 August 2013

Contents

Action

Configure the TWI (two wire serial interface).

 

 

Syntax

CONFIG TWI = clockspeed

CONFIG TWIC | TWID | TWIE | TWIF = clockspeed

 

(Config TWI is for ATMEGA and Config TWIX is for ATXMEGA chips)

 

Remarks

clockspeed

The desired clock frequency for SCL

 

 

CONFIG TWI will set TWSR pre scaler bits 0 and 1, and TWBR depending on the used $CRYSTAL frequency and the desired SCL clock speed.

Typical you need a speed of 400 KHz. Some devices will work on 100 KHz as well.

 

When TWI is used in SLAVE mode, you need to have a faster clock speed as the master.

 

XMEGA

The XMEGA can contain up to 4 TWI units. When not specifying TWIC, TWID, TWIE or TWIF, the TWIC will be used as  the default.

You MUST dimension a variable named TWI_START as a byte. It is used by the xmega TWI library code. Without it, you will get an error.

 

There are 2 manuals available from ATMEL for every ATXMEGA Chip

 

1. One Family Manual like for example for a ATXMEGA128A1 it is Atmel AVR XMEGA A Manual
2. Another Manual for the single chips like for example for an ATXMEGA128A1 it is the ATxmega64A1/128A1/192A1/256A1/384A1 Manual. In this Manual you find for example the Alternate Pin Functions. So you can find which Pin on Port C is the SDA and SCL Pin when you want to use the I2C/TWI Interface of this Port.

 

 

Notice.jpg
 It is important that you specify the proper crystal frequency. Otherwise it will result in a wrong TWI clock frequency.

 

 

See also

$CRYSTAL , OPEN

 

 

Example 


'-----------------------------------------------------------------------
' (c) 2004 MCS Electronics
' This demo shows an example of the TWI
' Not all AVR chips have TWI (hardware I2C)
'------------------------------------------------------------------------
 
'The chip will work in TWI/I2C master mode
'Connected is a PCF8574A 8-bits port extender
 
 
$regfile="M8def.dat"' the used chip
$crystal= 4000000 ' frequency used
$baud= 19200 ' baud rate
 
 
$lib"i2c_twi.lbx"' we do not use software emulated I2C but the TWI
 
Config Scl =Portc.5 ' we need to provide the SCL pin name
Config Sda =Portc.4 ' we need to provide the SDA pin name
 
'On the Mega8, On the PCF8574A
'scl=PC5 , pin 28 pin 14
'sda=PC4 , pin 27 pin 15
 
 
I2cinit' we need to set the pins in the proper state
 
 
Config Twi = 100000 ' wanted clock frequency
'will set TWBR and TWSR
'Twbr = 12 'bit rate register
'Twsr = 0 'pre scaler bits
 
Dim B AsByte, X AsByte
Print"TWI master"
Do
Incr B ' increase value
I2csend&B01110000 , B ' send the value
Print"Error : ";Err' show error status
I2creceive&B01110000 , X ' get a byte
Print X ;" ";Err' show error
Waitms 500 'wait a bit
Loop
End

XMEGA SAMPLE 

'----------------------------------------------------------------
' (c) 1995-2013, MCS
' xm128-TWI.bas
' This sample demonstrates the Xmega128A1 TWI
'-----------------------------------------------------------------
 
$regfile = "xm128a1def.dat"
$crystal = 32000000
$hwstack = 64
$swstack = 40
$framesize = 40
 
 
Dim S As String * 20
 
'first enable the osc of your choice
Config Osc = Enabled , 32mhzosc = Enabled
 
'configure the systemclock
Config Sysclock = 32mhz , Prescalea = 1 , Prescalebc = 1_1
 
Dim N As String * 16 , B As Byte
Config Com1 = 19200 , Mode = Asynchroneous , Parity = None , Stopbits = 1 , Databits = 8
Config Input1 = Cr , Echo = Crlf ' CR is used for input, we echo back CR and LF
 
Open "COM1:" For Binary As #1
' ^^^^ change from COM1-COM8
 
Print #1 , "Xmega revision:" ; Mcu_revid ' make sure it is 7 or higher !!! lower revs have many flaws
 
Const Usechannel = 1
 
 
Dim B1 As Byte , B2 As Byte
Dim W As Word At B1 Overlay
 
 
Open "twic" For Binary As #4 ' or use TWID,TWIE oR TWIF
Config Twic = 100000 'CONFIG TWI will ENABLE the TWI master interface
'you can also use TWIC, TWID, TWIE of TWIF
'!!!!!!!!!!! WITHOUT a channel identifier, TWIC will be used !!!!!!!!!!!!!!
 
#if Usechannel = 1
I2cinit #4
#else
I2cinit
#endif
 
 
Do
I2cstart 'since not # is used, TWIC will be used
Waitms 20
I2cwbyte &H70 ' slave address write
Waitms 20
I2cwbyte &B10101010 ' write command
Waitms 20
I2cwbyte 2
Waitms 20
I2cstop
Print "Error : " ; Err ' show error status
 
'waitms 50
Print "start"
I2cstart
Print "Error : " ; Err ' show error
I2cwbyte &H71
Print "Error : " ; Err ' show error
I2crbyte B1 , Ack
Print "Error : " ; Err ' show error
I2crbyte B2 , Nack
Print "Error : " ; Err ' show error
I2cstop
Print "received A/D : " ; W ; "-" ; B1 ; "-" ; B2
Waitms 500 'wait a bit
Loop
 
 
 
Dim J As Byte , C As Byte , K As Byte
Dim Twi_start As Byte ' you MUST dim this variable since it is used by the lib
 
'determine if we have an i2c slave on the bus
For J = 0 To 200 Step 2
Print J
#if Usechannel = 1
 I2cstart #4
#else
 I2cstart
#endif
 
I2cwbyte J
If Err = 0 Then ' no errors
 Print "FOUND : " ; Hex(j)
 'write some value to the pcf8574A
 #if Usechannel = 1
 I2cwbyte &B1100_0101 , #4
 #else
 I2cwbyte &B1100_0101
 #endif
 Print Err
 Exit For
End If
#if Usechannel = 1
 I2cstop #4
#else
 I2cstop
#endif
Next
#if Usechannel = 1
I2cstop #4
#else
I2cstop
#endif
 
#if Usechannel = 1
I2cstart #4
I2cwbyte &H71 , #4 'read address
I2crbyte J , Ack , #4
Print Bin(j) ; " err:" ; Err
I2crbyte J , Ack , #4
Print Bin(j) ; " err:" ; Err
I2crbyte J , Nack , #4
Print Bin(j) ; " err:" ; Err
I2cstop #4
#else
I2cstart
I2cwbyte &H71 'read address
I2crbyte J , Ack
Print Bin(j) ; " err:" ; Err
I2crbyte J , Ack
Print Bin(j) ; " err:" ; Err
I2crbyte J , Nack
Print Bin(j) ; " err:" ; Err
I2cstop
#endif
 
'try a transaction
#if Usechannel = 1
I2csend &H70 , 255 , #4 ' all 1
Waitms 1000
I2csend &H70 , 0 , #4 'all 0
#else
I2csend &H70 , 255
Waitms 1000
I2csend &H70 , 0
#endif
Print Err
 
 
'read transaction
Dim Var As Byte
Var = &B11111111
#if Usechannel = 1
I2creceive &H70 , Var , 1 , 1 , #4 ' send and receive
Print Bin(var) ; "-" ; Err
I2creceive &H70 , Var , 0 , 1 , #4 ' just receive
Print Bin(var) ; "-" ; Err
#else
I2creceive &H70 , Var , 1 , 1 ' send and receive
Print Bin(var) ; "-" ; Err
I2creceive &H70 , Var , 0 , 1 ' just receive
Print Bin(var) ; "-" ; Err
#endif
 
End
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