Let's Make Robots!

Bluetooth picaxe module

Hi, I have a picaxe 18m2 and a chi035a board and i would like to know if i have any possibility to pass information via bluetooth from a mobile to the picaxe, i'm just interested in the hardware, i'm not asking for software.

I have seen sparkfun.com site and I cant decide which module choose. Would  https://www.sparkfun.com/products/8497  that module work on my idea, otherwise could you say me which one would i need?

I really thank any help and I hope you have a solution to my project.

Gratefull, Nicolas.(excuse my english)

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6677: Thanks! :)


Could anybody else confirm that?

The RN41 is a very good Bluetooth module but not the best choice for your needs.

  • The Bluetooth module needs 3.3V power supply and 3.3v signal level. The PICAXE is a 5V device. You will need level shifters 5v->3.3V for signals and a 3.3V power source. 
  • The RN41 module is a SMD module with a smaller pinout than standard 0.1'' spacing. Difficult to connect wires to it.

Better buy a Bluetooth module including level shifter and power source like the BlueSMiRF silver. Or get a cheaper one from chinese eBay sellers, like this one.

thanks i'm buying ebay one, I still dont know how does the master-slave system works but I rely on you, I will investigate!



A few things about the cheap BT modules from eBay you should know:

  • The BT Modules can't be configured from the Bluettoth side, only from the serial UART side. This could be making trouble if the module is wrong configured. From the spec sheet it should work as slave, 38.4kBaud. This should work for you. If you need to change the setup, you will need a USB/UART module to connect the BT module on a PC and change the setup from a terminal program.
  • Be warned. Some eBay sellers sell similar modules with wrong or without any specs. See this thread

BTW. The BlueSMiRF can be configured from the Bluetooth side. 



omg why is everybody saying contradictory things?

I have already bought the ebay one, have i commited an error?



Hey Nicolas,

I did an Android app specifically for robots that might work for you. Send me an email, and I will send you a copy for you to play with if you would like. It will talk to your picaxe just fine.

The app is here


i'm completely sure that is a great build app, and i thank your gentlehood but as a school work i prefer to do it for myself.

Thanks!(could you tell me which is the average voltage that the 18m2 transmit to the modules?I'm doubting because the internet says different things)

Just like Yoda said, "there is or is not"

Your picaxe is a 5v system and will output whatever it is getting for a Vcc. This is of course, in its "5v mode" (the m2's can also be run at 3.3v). In either case, again, your digital outputs will send out whatever the Vcc is.

The key words you need to focus on here are "level shifting" and if your bluetooth modules have it. Most bluetooth units (the chip itself) are usually 3.3v devices, however some bluetooth breakout boards include level shifting circuitry and can thus, be operated at 5v. 

Double check the comments above on the same topic and check your datasheets. 

ok, i'm almost done, my bT module has 2 modes one 3.3V and a Second with 5V. Thanks for all your help you have been really helpfull

ok, i'm almost done, my bT module has 2 modes one 3.3V and a Second with 5V. Thanks for all your help you have been really helpfull