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Sunday, 10 November 2013

The case for lurking on LMR before starting on a large (ish?) robotics venture...

Ok... so let me start with...

 I've been humbled by the sheer simplicity with which some of these bots on LMR (Lets Make Robots) are made.  Functional and clean.



The one article that has made me rethink my strategy the most is  Oddbot's article Pushing the limits with encoders

In my Robot here, I use a RaspBerry Pi to talk to two Arduino's via Serial over USB.  The premise being that the USB was already there for programming... might as well use it for communications. Then one of the Arduino's is also an I2C master to various sensors, that it then translates into serial feeds for the RPI.... hmmmmm....  can anyone say "inefficient"? 

I *had* investigated the option of using the RPI as a I2C master, and the two Arduino's, along with all of the I2C sensors would become slaves... looking back, I passed up on this quickly because I would have had to build or buy a level converter.... really?

I've spent probably close to $500-$600 on this thing so far... and yet a few bucks... or more likely an hour at the soldering iron made my decision for me.


I've struggled for WEEKS on timing issues related to getting commands accurately into the Arduino running the motors (using the Motorshield V3) which uses two PWM drivers, as well as the two servos .... The UNO fully consumes Timer 0/1/2 to take care of these, and so all code has to be devoid of "delay()" or "millis()"....  Sending a Serial command formated with specific start character, as well as a command UID to be used to validate completion of the command back to the RPI.

So.....

I'm going to step back for a week... regroup... reassess what functions are best suited to which processor, and clean it up.

Raspberry PI being I2C Master.   Arduino UNO retaining Motor control as well as Wheel encoder and IR proximity, but as an I2C slave as opposed to "Serial - hope-it-gets-interpreted-properly".
As I was simply replaying the I2C sensors via serial for the RPI to interpret, store, react, anyway.... This will be a workload removed from the UNO.
I will still dedicate the Arduino FIO to managing the Sonar POD servos and MAXSonar EZ1s, for now... but will communicate with the RPI as an I2C slave.

I may ultimately be able to eliminate one of the Arduino's .... but we'll save that for the next robot.

Any suggestions, tips, words of kindness... laughter...  bring it on...


References:

http://blog.oscaraConnect Raspberry Pi and Arduino with Serial USB Cable
Raspberry Pi and Arduino Connected Using I2C
Raspberry Pi and Arduino Connected Over Serial GPIO
Step by Step Guide on Making an I2C Slave Device with an Arduino
Arduino.cc: Arduino as I2C Slave ?
Instructables: I2C between Arduino's
http://digitalcave.ca/resources/avr/arduino-i2c.jsp
Raspberry Pi master controls Arduino UNO slaves via I2C
I2C communication between a RPI and a Arduino