Advice about Small microcontroller

Dear Arduino forum,

So far, I’ve gotten great help from here, and I hope I can get it again. I am quite new at this, but have managed to complete a few projects mostly on my own. I am starting on a new project and I have figured out how I want to set it all up. Essentially, I want to make a small locking mechanism, which is driven by a small motor that has to only turn between 0 degrees and 180 degrees to drive a special spring. I also want a microcontroller that can control the motor when it receives a bluetooth signal. The problem I am having is finding a microcontroller and a bluetooth module for my project that is the right size. The place where the microcontroller and bluetooth module can sit is around 30mm x 30 mm x 20 mm (Which makes the Ardunio Nano and Pro Mini a bit to long for the job). So far I have found some that could be usable, but they either had bad reviews or the stores I’ve checked don’t sell them anymore. As an example, I found the RedBearLab BLE Nano Kit v2, but the place I found that supposedly sold it didn’t any longer (and the reviews for the kit were not good from what I have found). I’m curious to hear if anyone has any experience working with very small microcontrollers that they would like to recommend? I have seen someone talk about an ATtiny85, but I am unsure if that can be hooked up in a way so it can receive a bluetooth signal. Might there be someone with experience in that department? Otherwise, I would just like to ask for general ideas on how I could control the motor in another way; any ideas that might help would be great.

Thank you for reading my post, and I hope you have a good day.

How about Adafruit's trinket M0 and Bluefruit LE module?

Disclaimer: haven't used either.

Hello, Lasse_E_J,

ATtiny85 is perfectly fine for this task. Cheap Aliexpress BT modules usually communicates via RX/TX serial, so serial bitbanging will be required (I think libraries already exist for that). Also find BT module that is right size for your project. Keep in mind that most BT modules run on 3,3V. I assume you're going to use servo motor, so this setup should work fine.

3Dgeo: ATtiny85 is perfectly fine for this task. Cheap Aliexpress BT modules usually communicates via RX/TX serial, so serial bitbanging will be required (I think libraries already exist for that).

If you use DrAzzy's Tinycore for the ATTiny then Serial functions out of the box (almost) exactly like on a normal Arduino.

BJHenry: If you use DrAzzy's Tinycore for the ATTiny then Serial functions out of the box (almost) exactly like on a normal Arduino.

Nice, it's a while I've played with ATtiny85 :)

Or if you want hardware serial in a similarly small package (smallest is 3x3 or 4x4 mm) look at the ATtiny841. A very capable Tiny. Two hardware Serial, one 8-bit and two 16-bit timers, the only thing is that it can only go to 16 MHz, not 20 MHz like its predecessor, the ATtiny84a.

Indeed you can use Serial and it'll use hardware when available or software when needed with that core. Pretty small an implementation, too.

3Dgeo: Cheap Aliexpress BT modules usually communicates via RX/TX serial,

Most if not all Bluetooth modules that I've looked at so far use Serial communication.