This document discusses how to set up two I2C interfaces on an Attiny841 microcontroller. It evaluates using an Arduino Uno and two Adafruit sensors connected to the Attiny841 via I2C. It recommends using libraries like WireS and software I2C to implement the two I2C interfaces without hardware support. Sample code is provided that controls both I2C interfaces simultaneously on the Attiny841.

1. How to setup two I2Cs
on Attiny841
Yoshinobu Tanno
http://ytanno.herokuapp.com/

2. Assumed structures
User Controller/
Board on
Attiny841
The other
communication
or voltage
Sensor
Board on
Microcontroller
The other
communication
or voltage
Sensor
Board on
Microcontroller
The other
communication
or voltage
Sensor
Board on
Microcontroller
The other
communication
or voltage
Sensor
Board on
Microcontroller
The other
communication
or voltage
Sensor
I2C Wire

3. Goal
• How to setup two I2Cs on Attiny841
Board on
Attiny841
Sensor

4. Evaluation environment
Arduino Uno
A4 A5/
PA6 PA4
Attiny841
PA3 PA0
Adafruit
MPL3115A2 - I2C
Barometric Pressure/Altitude/Temperature Sensor

5. Use of library
Arduino Uno
A4 A5/
PA6 PA4
Attiny841
PA3 PA0
Adafruit
MPL3115A2 - I2C
Barometric
Pressure/Altitude/Temperature
Sensor
WireS for I2C Slave
https://github.com/nadavmatalon/WireS
Attiny841 Core
https://github.com/SpenceKonde/arduino-tiny-841
Software I2C.
https://github.com/ytanno/Attiny841TwoI2CSample/blob/master
/Attiny841Side/yt_make_libraries/MySoftI2CM/mySoftI2CM.h
or other file

6. Sample of Atmel Studio Reading Path

7. Library Place Sample

8. Sample Code
Controls Two I2Cs
• You can download
https://github.com/ytanno/Attiny841Tw
oI2CSample/blob/master/Attiny841Side
/Attiny841_TwoI2CDemo_20190130/Att
iny841_TwoI2CDemo_20190130/Attiny
841_TwoI2CDemo_20190130.ino