Trying to get two Arduinos to communicate via Bluetooth, help please!

Thread Starter


Joined Sep 24, 2016
Hi everyone,

I'm trying to get two Arduinos to communicate via Bluetooth. Each Arduino uses an AT-09 BLE module and individually each can successfully communicate with a Serial Terminal app on my phone. However, the two modules fail to communicate with each other. My setup is a follows:
I have an AT-09 module set as a slave and connected to an Arduino. The Arduino code simply sends a char array to the BT module every 5 seconds. I can successfully receive these transmissions on my phone with Kai Morich's Bluetooth Serial Terminal app.
I have a second AT-09 module set as a master and connected to a second Arduino. The Arduino code simply performs a bidirectional pass-though function. Anything that is received by the BT module is passed to the Arduino IDE Serial Monitor, and correspondingly anything that is typed into the Serial Monitor is passed to the BT module. This code works perfectly well when the BT module is in AT mode - I can successfully use the Serial Monitor to send AT commands to the module and receive the command responses from the BT module. The code also works perfectly well if I set the BT module to slave, and send data back and forth to/from the app on my phone.
In order to get the two modules to communicate with each other, I have set the BT master module to bind with the slave, they appear to connect successfully (LEDs on both modules stop flashing and are continuously on; master stops accepting AT commmands, indicating that it's in comms mode). However, the char array sent from the slave does not appear to be received by the master - no data appears at the Serial Monitor. I'm new to BT, so I'm not sure what I could be missing.
Any thoughts on this? Many thanks!