Yet another MMR-70 project

ATmega32L and radio sender for 70 euro-cents

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Some playing around with the MMR-70 radio module


After reading about the MMR-70 in this project #MMR-70 - cheap radio module. I needed to order some myself. Here I will write something about it. I would also thanks @Dr Salica. I will use some code from his #Portable Trollmaster 3000 in the furture.

Things I did so far

  • Writing code for the Atmega32 to generate some tones
  • Adapting the Trollmaster3000 code to use it with Atmel Studio and without the Arduino wire library
  • Feeding the Music generated on the Timer2 output into the radio module to sent it.
  • replacing the resonator to get more CPU power (for example: KYOCERA PBRC16.00HR70X000)


  • better sound quality ... this square waves does not sound good
  • Replacing the voltage regulator to a 3.3V or 5V type (MIC5205-3.3YM5 or similar) ATTENTION: The radio module's max supply voltage is 3,6V!!!

Some sources, used libraries and tools

@Dr Salica #Portable Trollmaster 3000

@davedarko #MMR-70 - cheap radio module Forum: schematic, data sheet of the radio module and a forum thread (German)

@Tobias Mädel: FMBerry - also some description of the hardware

Peter Fleury , i2c library for AVRs

  • 1 × MMR-70 radio module radio module for Sony Ericsson mobile phones
  • 1 × Wires, solder and other misc stuff

  • New Resonators arrived

    Alex09/20/2015 at 13:38 1 comment

    The 16MHz resonators I did ordered arrived. Thy do have the same footprint as the original 3,6864MHz resonators. In the picture you can see the new (top) and the old (bottom) resonator

    With a hot air station it was easy to change the resonator. And the Atmega32L does run at 16MHz and supply voltage of only 2.8 Volts (this is according to the datasheet out of spec). 3.3V regulators are ordered, so I will l try them also.

  • It'S playing some music

    Alex09/14/2015 at 19:52 1 comment

    Tone is created by a simple square wave. Next I will try to load a small wave file onto the ATmega. This should sound better than.

  • It's working

    Alex09/13/2015 at 15:43 0 comments

    With help of the code from the Trollmaster3000 I did managed it to work. More later or tomorrow....

    The two cinch connectors on the left are one input of the radio and a one output of the Atmega connected together. The Atmega creates some tones. Also about this tones I will write something more soon.

  • Attaching wires to the board

    Alex09/12/2015 at 19:04 0 comments

    For playing with the MMR-70 board i did add some wires. First I added A ISP_programming header to reprogram the ATmega32L and some power supply wires. On the the picture you can also see my second step: desoldering the led to get access to pin PD7 (the blue wire) and a new LED connected between the original Led resistor and PB0/PAD4. PD7 can be used by the output compare unit of Timer2 to generate simple square waves.

    So far did not used the radio modul itself. Frist I will try to generate some tones, to transmitt them later

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Manawyrm wrote 09/12/2015 at 19:03 point

Always interesting to see people building cool stuff with these modules. Keep us updated ;)

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davedarko wrote 09/12/2015 at 20:45 point

Hey Tobias, I remember seeing one of your videos on youtube where you prepared a module. And looking for it now, I notice that the FMberry is actually your work?! nice.

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davedarko wrote 09/12/2015 at 18:33 point

Interesting, looking forward to see what you come up with. Where did you get yours? 10 pack on eBay as well?

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Alex wrote 09/12/2015 at 18:39 point

Yes the 10 pack from ebay. 

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davedarko wrote 09/12/2015 at 21:11 point

btw, you've linked your project as my project in your sources ;) and the radio thing on the mmr-70 takes only up to 3.6V, so be careful with the 5Vs - but then again 70ct board and you have 10 of them :)

  Are you sure? yes | no

Manawyrm wrote 09/12/2015 at 21:19 point

as davedarko said: be a little bit careful with the 5V idea. The NS741 transmitter chip doesn't really like 5V even on its I/O lines, I had strange errors/misbehaviour by doing that. 

@davedarko: yep, FMberry is my project :)

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Alex wrote 09/13/2015 at 08:01 point

that's right using  5V is probably not the best idea. I will first try whether the ATmgea16 will run at 16MHz and 3.3V. If not I will go down with the frequency or power the ATmega from an extra regulator.

  Are you sure? yes | no

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