I2C

Matthias Trute mtrute@web.de Version 1.0.3 - 2017-04-30

This package provides some more or less generic I2C related words. They are generic in a sense that they depend on a low level hardware driver, that provides some very basic routines to access the I2C interface. They are based on the amforth recipe http://amforth.sourceforge.net/TG/recipes/I2C-Generic.html

They are tested with amforth on an Atmega with it's hardware I2C module called TWI.

The driver uses the following hardware low level words, that the user has to provide.

i2c.wait ( -- ) wait for the bus

i2c.start ( -- ) send start condition

i2c.stop ( -- ) send stop condition

i2c.restart ( -- ) send the restart condition

i2c.tx ( c -- ) send 1 byte

i2c.rx ( -- c ) receive 1 byte, send ACK

i2c.rxn ( -- c ) receive 1 byte, send NACK

The following two words are not essential but are useful for tools and checks.

i2c.status ( -- n ) get i2c status in a system specific way

i2c.ping? ( addr -- f ) detect the presence of a device on the bus, f is true if a device at addr responds

i2c.frt

above the specific driver words some generic but still low level words.

i2c.begin         -- starts a I2C bus cycle
i2c.end           -- ends a I2C bus cycle
i2c.n!            -- send n bytes to device
i2c.n@            -- read n bytes from device

i2c-detect

This command scans the bus and prints a small overview over the addresses that respond to the ping.

(ATmega1280)> i2c.detect 
      0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
 0:                       -- -- -- -- -- -- -- -- --
10:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20:  -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40:  -- -- 42 -- -- -- -- -- -- -- -- -- -- -- -- --
50:  50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60:  -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70:  -- -- -- -- -- -- -- --                        
 ok

The tool and the output is designed to mimic a linux tool of the same name.

i2c-eeprom*

The 24Cxx chips using 2 byte addresses are supported. The interface uses the block wordset API. The API transfers the standard block size to a fixed block buffer defined outside of this package.