I2C Slave Library (Download version)

Price: EUR 14.95

This product is provided as down-loadable without any storage media and is billed without shipping.

I2CSLAVE is an add-on product for BASCOM-AVR.

It allows you to turn an AVR micro into an I2C slave chip.

You could start your own factory for I2C chips: create your own PCF8574 , I2C LCD display etc.
The I2C Slave add on comes with different libraries for different AVR processors.

There is the plain soft mode library which uses the TIMER and INT interrupts and it is intended for the older AVR chips which do not have TWI or USI like  2313,2323, 2333,2343,4433 and tiny22.

Then there is a Library for AVR processors that have built in TWI hardware (TWI-I2C).
This should be used for processors like M8,M32, M64,M128, M644, etc.

And  most TINY processors come with an USI. There is a library that can be used with the USI as well. This is for processors like : tiny2313,  tiny4313,  tiny24,  tiny44,  tiny 84, tiny25,  tiny45 , tiny85,  tiny26,  tiny261,  tiny461, m169, m165 , m325,  m3250,  m645,  m6450,  m329,  m649, tiny87,  tiny167 and tiny43U

For the XMEGA there is a separate library. 

The library works similar for all libraries but there are subtle differences. Use the examples and the help to get started.

While a big range of the AVR processors is supported with a library, not all AVR’s can be turned into an I2C slave.
Here is a small sample for the atTiny2313 with USI.
 

'-------------------------------------------------------------------------------
'                            (c) 2004-2014 MCS Electronics
'          This demo demonstrates the USI I2C slave
'          This is part of the I2C Slave library which is a commercial addon library
'          Not all AVR chips have an USI !!!!
'-------------------------------------------------------------------------------
$regfile = "attiny2313.dat"
$crystal = 8000000
$hwstack = 40
$swstack = 16
$framesize = 24
const cPrint = 0                                            'make 0 for chips that have NO UART, make 1 when the micro has a UART and you want to show data on the terminal
#if cPrint
 $baud = 19200                                            'only when the processor has a UART
#endif
config usi = twislave , address = &H40                      'bascom uses 8 bit i2c address (7 bit shifted to the left with one bit)
#if cPrint
 print "USI DEMO"
#endif
'do not forget to enable global interrupts since USI is used in interrupt mode
enable interrupts 'it is important you enable interrupts
do
 ! nop ; nothing to do here
loop


'The following labels are called from the library. You need to insert code in these subroutines
'Notice that the PRINT commands are remarked.
'You can unmark them and see what happens, but it will increase code size
'The idea is that you write your code in the called labels. And this code must execute in as little time
'as possible. So when you slave must read the A/D converter, you can best do it in the main program
'then the data is available when the master requires it, and you do not need to do the conversion which cost time.

'A master can send or receive bytes.
'A master protocol can also send some bytes, then receive some bytes
'The master and slave address must match.
'the following labels are called from the library  when master send stop or start
Twi_stop_rstart_received:
 '  Print "Master sent stop or repeated start"
Return
'master sent our slave address and will not send data
Twi_addressed_goread:
 ' Print "We were addressed and master will send data"
Return

Twi_addressed_gowrite:
 '  Print "We were addressed and master will read data"
Return
'this label is called when the master sends data and the slave has received the byte
'the variable TWI holds the received value
Twi_gotdata:
 '   Print "received : " ; Twi ; " byte no : " ; Twi_btw
 Select Case Twi_btw
 Case 1 : 'Portd = Twi                                   ' first byte
 Case 2: 'you can set another port here for example
 End Select
Return
'this label is called when the master receives data and needs a byte
'the variable twi_btr is a byte variable that holds the index of the needed byte
'so when sending multiple bytes from an array, twi_btr can be used for the index
Twi_master_needs_byte:
 '  Print "Master needs byte : " ; Twi_btr
 Select Case Twi_btr
 Case 1 : twi = 68                                       ' first byte
 Case 2 : twi = 69                                       ' send second byte
 End Select 'you could also return the state of a port pin or A/D converter
Return