EXTENDED I2C

Action

Instruct the compiler to use parts of the extended i2c library

 

 

Syntax

$LIB = "i2c_extended.lib"

 

 

Remarks

The I2C library was written when the AVR architecture did not have extended registers. The designers of the AVR chips did not preserve enough space for registers. So when they made bigger chips with more ports they ran out of registers.

They solved it to use space from the RAM memory and move the RAM memory from &H60 to &H100.

In the free space from &60 to &H100 the new extended register were located.

 

While this is a practical solution, some ASM instructions could not be used anymore. This made it a problem to use the I2C statements on PORTF and PORTG of the Mega128.

The extended i2c library is intended to use I2C on portF and portG on the M64 and M128.

It uses a bit more space then the normal I2C lib.

 

Best would be that you use the TWI interface and the i2c_twi library as this uses less code. The disadvantage is that you need fixed pins as TWI used a fix pin for SCL and SDA.

 

 

See also

I2C

 

 

ASM

NONE

 

 

Example

'-------------------------------------------------------------------------------
' (c) 2005 MCS Electronics
' This demo shows an example of I2C on the M128 portF
' PORTF is an extened port and requires a special I2C driver
'-------------------------------------------------------------------------------
 
 
$regfile = "m128def.dat" ' the used chip
$crystal = 8000000
$baud = 19200 ' baud rate
 
 
$lib "i2c_extended.lib"
 
Config Scl = Portf.0 ' we need to provide the SCL pin name
Config Sda = Portf.1 ' we need to provide the SDA pin name
 
 
Dim B1 As Byte , B2 As Byte
Dim W As Word At B1 Overlay
 
 
I2cinit ' we need to set the pins in the proper state
 
 
Dim B As Byte , X As Byte
Print "Mega128 master demo"
 
 
Print "Scan start"
For B = 1 To 254 Step 2
I2cstart
I2cwbyte B
If Err = 0 Then
 Print "Slave at : " ; B
End If
I2cstop
Next
Print "End Scan"
 
 
Do
I2cstart
I2cwbyte &H70 ' slave address write
I2cwbyte &B10101010 ' write command
I2cwbyte 2
I2cstop
Print Err
 
 
I2cstart
I2cwbyte &H71
I2crbyte B1 , Ack
I2crbyte B2 , Nack
I2cstop
Print "Error : " ; Err ' show error
Waitms 500 'wait a bit
Loop
End

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