Arduino Micro and JY-MCU V1.05

Hello there!

I’ve just purchased an Arduino Micro and I am having problems at connecting it to a TTL<->Bluetooth serial adapter.

The device I am trying to connect it to is a JY-MCU V1.05 with the firmware linvor1.8. This device seems to work perfectly with my old Arduino Diecimila, but when I try to connect it to my Arduino Micro nothing happens.

The device is meant to work with 3.3V logic levels but as I said, it works perfectly with the Arduino Diecimila.

What could be happening not to let this devices talk to each other?

Thanks for reading.

I was having almost the exact same issues with almost the exact same hardware. I had my JY-MCU v.1.05 working with my UNO. The code didn't work with my Micro. To keep this simple, I will describe my setup for you to take away what you can: BT VCC --> Micro 5v (Yes, I have read that this particular module likes the 3.3V, but this worked for me, so I'm sticking with it) BT GND --> Micro GND BT TXD --> Micro RX BT RXD --> Micro TX

Tools > Board > Arduino Micro

Read up on some of the necessary parameters for the Arduino Micro here >> I learned about the Serial1 thing from that page.

And, I know how it feels to read about someone's successful code, wishing they had just posted it... so, here it is:

// This is the code I scrapped together to test my bluetooth APP with a // Freeduino Micro V1.4 and a JY-MCU V1.05 // The Freeduino Micro has the exact same hardware as the Arduino brand // Note lines 14, 15, and 16. I believe these are necessary for both Micro brands

int pin = 13;

void setup() { pinMode(pin, OUTPUT);

Serial1.begin(9600); while (!Serial1) { ; } }

void loop() {

if (Serial1.available()) Serial1.write(;

switch( { case 'a': { digitalWrite(pin, LOW); break; } case 'b': { digitalWrite(pin, HIGH); break; } default: { break; } } }

RandomSim: The device is meant to work with 3.3V logic levels What could be happening not to let this devices talk to each other?

The JY-MCU is meant to be powered by 3.6 to 6v, as should be, and probably is, clearly marked on the back. Assuming the code for both devices, and the Uno, is the same. the connection should be the same and it appears that for the Micro and Uno it is, namely D0,D1 labelled Rx,Tx.

If your connections are OK, your problem may be the USB cable still being connected to the PC.

Had to chime in – I’ve been beating my head over this for several days. One late, groggy night, I let the smoke out of one of my Micros by miss powering it. I was sure it was because I still had the USB connected. I quickly used my 12V wall adapter I use on my Uno and smoked the Micro! Guess the regulator in the Micro isn’t as sturdy as the Uno’s. I diverge…

Anyhow, after hours of various Google searches, finally fell on this thread! I must have read the Micro page a dozen times and every time I missed that little “1” after Serial in one place. Thanks RandomSim for having the problem and mldeboer for the gentle reminder of how the devil is in the details. I was about to fry the second one out of spite! :smiling_imp: