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Topic: HC-05 bluetooth module recieves (some) AT commands, will pair, but will not conn (Read 74 times) previous topic - next topic


Greetings all. I am attempting to create a bluetooth LED project with my son for fun. My coding experience is limited to Matlab, and this is my first attempt to use a bluetooth module. I have an arduino UNO, HC-05 bluetooth module, and LG-V20 android telephone. I have set pins D2 as Rx and D3 as Tx. I have connected wires from pins 4 and 5 to VCC of the HC-05, gnd to gnd. I have run a voltage divider from D3 to the HC-05 to reduce the voltage down to 3.3v. I have set up pins D6-8 to run MOSFETs to modulate the LED strip. All of which has been successful recently. I have used MIT app inventor 2 to create an android application that theoretically allows me to control the RBG combinations sent to pins D6-8.

The issue I am having is that my connection to my bluetooth module is sketchy at best. I was able to connect properly when I finished for the evening last night, and powered everything down (still working on reading RGB combinations properly). However, this morning, I am no longer able to connect my android device to the bluetooth module. I am able to pair the device, I am able to send AT commands (some anyways), but when I attempt to connect I recieve an error message which varies depending on the application I use to attempt my connection. The MIT app inventor message says to make sure the bluetooth client is powered on. Thinking that this might be an issue with MIT app inventor, I downloaded "Bluetooth Terminal HC-05" from Google Play. Again, I am able to pair with the device, but receive the error, "May be your HC-05 device is not available for connection Or you are trying to connect with other device." I can pair and unpair from the module, so I know that it is transmitting and receiving a signal. I have checked all of the voltages on the pins, and they are (RXD)3.28v, (TXD)3.3V, (GND) 0.005V, (VCC) 5.1V.

Thinking that it might be something faulty with the HC-05 module, I purchased a second one, but am getting the same results. When I use the serial monitor to communicate with the HC-05 module, I get the following results:







This is the second time that the module has done this to me. It quit on me last week for a couple of days, and then started up again, and I have no idea what I changed to get it back, but it only lasted a day this time. Any help/suggestions would be greatly appreciated. I have attached my .ino file below.

Thank you,


but receive the error, "May be your HC-05 device is not available for connection
This will be true if it is still in AT mode.

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