Tag Archives: Bluetooth

HC-05 Bluetooth: Using AT commands

A couple of weeks ago I posted a discussion about using a Bluetooth HC-05 module to control one of my WALL CLOCKs. One of the issues I faced was not being able to reliably control one of the two modules that I purchased using AT commands.  One worked while the other didn’t and I couldn’t figure out why.

HC-05 Module

HC-05 Module

So, with a little bit of time to kill, and a very helpful instructable, I tried to get the errant unit into AT-mode. Again, no luck!

While there are many discussions online about this issue, I could not find one that related specifically to the module I had. In my case the mode select pin of the HC-05 daughter board is not brought out to the pins of the carrier. But by tracing the layout, I worked out how to wrestle this little bugger into AT command mode and reset the unit to its factory default settings.  Thank Odin for Internet!

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MIT App Inventor 2…

In order to remove all of the mechanical methods to set the time, colours and light intensities of my clocks, I’ve been playing with Bluetooth as a simple wireless interface to my Android phone or, indeed, any laptop. So far, I have been using the BlueTerm terminal emulator app to simply read status and write settings. However, I wanted something a little flashier and came across the MIT App Inventor 2 software development environment.

Woo hoo!  What a neat tool!

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Bluetooth – perfect for setting clocks!

Over the past couple of months I have been playing with a Bluetooth module that I purchased some time ago from eBay. I purchased the small 3.3V Bluetooth module and a carrier interface (with level shifters) to make it easier to use on a breadboard and interface to the 5V Arduino boards.

HC-05 BlueTooth module

HC-05 Bluetooth module

HC-05 BlueTooth Carrier Interface

HC-05 Carrier Interface






After soldering the units together, rather than just play with the unit, I started to mess with the AT-command interface and appear to have set it to some weird and unresponsive state. Finally, my patience got the better of me and I put it aside.

Last night, I decided to play with it again and got it working, sending data to and receiving data from an Arduino Nano. Bing!  A light went off. I would use Bluetooth to allow me to use my Android cell phone to  control all of the functions of my wall clock, including setting its time. Yeah, baby!

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