I2C Rpi and arduino

I've connected a 44780 based LCD to the Pi via I2C but I haven't tried talking to the Arduino using this interface.  Have you gotten I2C to work on the Pi?  There are a lot of useful links describing how to do this: http://www.skpang.co.uk/blog/archives/575  and http://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c for example.  Since I'm using a MCP23017 based I2C I followed the two programming links on this page  http://mypishop.com/Protect%20Your%20Pi%20!.html

This link seems to have some useful info when you're ready to connect the Arduino to the Pi.

http://blog.oscarliang.net/raspberry-pi-arduino-connected-i2c/

This link notes that you need to pay careful attention to the differing voltage levels.

You could also use the serial lines. Both the Pi and the Arduino will have tx and rx pins. Again, you may need a level converter, but you can communicate up to 115200 baud.

You didn't mention what kind of arduino you have but the tx and rx are on pins 0 and 1 on the uno style and on gpio pins 14 and 15 on the pi.

You can actually get an arduino pro mini that runs at 3.3v so you won't need the level conversion. I've seen them as cheap as $10.

Have fun.

Mike

Michael Conners wrote:

 

You could also use the serial lines. Both the Pi and the Arduino will have tx and rx pins. Again, you may need a level converter, but you can communicate up to 115200 baud.

 

You didn't mention what kind of arduino you have but the tx and rx are on pins 0 and 1 on the uno style and on gpio pins 14 and 15 on the pi.

 

You can actually get an arduino pro mini that runs at 3.3v so you won't need the level conversion. I've seen them as cheap as $10.

 

Have fun.

 

Mike

I like this answer.  If your intent is serial communications and not just learning I2C, this sounds like a better approach.

Yes the intent is to use the arduino uno as data input output both digital and analogic pared with the Rpi to handle control of many many many stuf that the Rpi cant connect to and use the arduino as a serial in and out, I allready have a program for multiplying the arduino ins and outs to an unlimited amount using multiplexers on the input and shift registers on the out, they even have memory to store the data temporary when reading or writing to the outside.

Its very cool and I cant wait to control it with the Rpi. thanks for the ingo I will look in to it and blog the end results with the code files and diagrams for anyone to use thanks again.

Dave Guthridge wrote:

I like this answer.  If your intent is serial communications and not just learning I2C, this sounds like a better approach.

I agree, since I wrote it. But it is an easy approach, I think you can redirect the serial IO on the arduino pretty easily and using pyserial you can get to /dev/ttyAMA0 (the serial port) on the pi pretty easily as well. The bandwidth should be plenty for control and status comms. You may have to turn off the console on the pi though. http://elinux.org/RPi_Serial_Connection

You can do it with I2C or even SPI, but I'd go with the simpler approach.

Mike

Antoher link to turning off the serial port on the pi http://www.hobbytronics.co.uk/raspberry-pi-serial-port

More straightforward.

Mike

I keep thinking of stuff, another great advantage is you can fire up a terminal program on the pi and test your interface on the arduino. So that way you can debug your command/response interface.

Fun stuff.

Mike