3PI + WiFi

Hi, im working on a project, and its basically to connect the 3PI with the RN-131g Breakout wifi module which has a maximum 3.3V (sparkfun.com/commerce/produc … ts_id=9333) .

what i understand for the guide is, that the PD0 and PD1 works on 5V. this will damage the Wifi module.

My solution is:
“UART: Connect a common ground when using the external TX, RX inputs. For a 3 wire DB-9 interface (connect tx, rx, gnd only) The reset pin is 3.3V tolerant Factory default is hardware flow control disabled, CTS and RTS are not required. When using a 5.0 VDC Input, PIO’s and UART input pins require a resistor divider. A suggestion is 10K in series with 20k to ground. PIO’s are 0-3.3 VDC not 5.0 VDC tolerant.”

My questions are: is there a the pull-up resistor on the 3PI?, Do you know if i could integrated this module to the 3PI with out getting damage?

as you might know if there is a pull-up resistor on the TX, RX , the changes of making the wifi the transmit enough voltage to the 3pi microntroller will be small.

could you please give some guidelines how to solve the small issue?

thank you


The 3pi’s RX pin (PD0) is internally pulled high when the UART module is enabled. This pull-up is probably between 20 and 60k, but you can check the ATmega328 datasheet for more exact specifications, and you can easily test the strength of the pull-up with a resistor and multimeter. The AVR should be able to detect 3.3V serial signals, but you should check the electrical characteristics section of the datasheet to be sure. The TX pin (PD1) is a driving output; you will need to put a voltage divider between this pin and your module.

- Ben

Hi there… My pololu has atmega328
Im try to compile a code that i have created in arduino, im using arduino 12 which you recommend on the guide , i have change all the settings. i haven’t had the luck to get it to work !..

the error message is:

avrdude: Expected signature for ATMEGA168 is 1E 94 06
Double check chip, or use -F to override this check.

Now i’ m stuck could someone help plz???


I recommend using AVR Studio and WinAVR as your IDE and compiler along with the Pololu AVR library since our Arduino support has not been updated recently and is somewhat out of date, but you can probably still get it working with minor changes. Follow the instructions in section 3 of our Orangutan Arduino guide, except change these parameters in your boards.txt file to have the following values:


Please let me know if this gets things working for you.

- Ben

Hi Ben.

I have give up with arduino. I will have to go with AVRstudio. now i would like to ask you for some guidelines:

This is my final project of my degree, i have two weeks left and its now down to programming the 3pi to making do what i need it to do. (I’m pretty much a beginner in programming, I took this project as a challenge).

how could i initializes the 3pi to listen and transmitted from the wifi module (rovingnetworks.com/documents/rn-131-ds.pdf). i connect the wifi module in to the 3pi using. PD0 and PD1 + GNR + VBATT.

thank you

It looks like the simplest interface supported is TTL serial, so you should look at the OrangutanSerial portion of the Pololu AVR library:


Note that the 3pi communicates using 5V signals and your wifi module runs at 3.3V, so you should make sure that the wifi module’s RX pin is 5V-tolerant. I didn’t see anything about this in the datasheet you linked, but I didn’t look very carefully. If it isn’t 5V-tolerant, you should use an intermediate circuit to shift the voltage level or else you might damage your wifi module.

- Ben

Thank you Ben.

I did notice that, and i have created and voltage regulator, which is operational right now! so hopefully i will be able to share my project success with you.

As i said before and quite new on this programming stuff! so i will try to figure out how to make it work…

thank you for your support! ill let you know how i am getting on with it

Good luck with your project. I look forward to hearing more about it as it progresses!

- Ben

Hi Ben , just wanted to say thank you for the support, and guiding, it really contribute in my project.

Fortunately the my project works now! and the presentation was really good! so add to your profile (3pi + Iphone = Works)

many thanks again, and keep it up, amazing devices love it!

I commend boitelj for making the 3pi + WiFi + iPhone combination work. I was able to do the same sort of thing that I suspect boitelj accomplished (WiFly GSX from Roving Networks mounted on 3pi in order to receive commands from an iPhone via WiFi). Just wanted to share my work on here:

Thanks for making the 3pi a joy to use/develop on!