What’s cooking @ e-Gizmo Episode 5: Low Cost Bluetooth Module

e-Gizmo upcoming Bluetooth Module is a class 2 discoverable UART wireless cable replacement device. It is logic compatible with 3.3V logic UART devices (MCU). A simple level translator is needed to interface it with 5V logic system. It costs much less compared to its older soon-to-be retired kins.p>

 

 

For something like a year, I’ve been scouting several supplier of Bluetooth module in search of a more affordable alternative to our existing models.  The quest had so far, had been discouraging. I purchased quite a number of samples from several Chinese manufacturers, unlucky me somehow, I always received samples that are either not built for UART wireless replacement applications (no SPP profile), or for some reason, are invisible to a master Bluetooth host (i.e. cannot be paired with a PC Bluetooth). English Instruction manuals, if I get lucky enough to obtain one, are obviously machine translated hence largely unreadable. Trying to figure out what each sentence means takes a lot of hard work, and often leaves me more confused than before when I started. On-line support did not helped either, not that they are not willing to help, I suspect it’s the language barrier having its way.

 

The sample module that is the subject this blog actually arrived as early as January this year – about the time when I basically lost interest and gave up looking. Hence these modules went straight to my “might-be-useful-someday” scouring box. As fate would have it, I suddenly had an urgent need for a Bluetooth module, and these modules finally got the attention they deserved. And to my pleasant surprise, unlike those that came before it, these modules are in fact programmed and works as serial cable replacement!

 

 

 

 

 

 

 

The modules that I currently have- lets give it a tentative name as EGBT04S- is loaded with firmware pre-configured as slave only. This is not a problem at all if you intend to use it to connect with a PC or another Bluetooth master device. In fact, users will quickly benefit from it in that only a few user setups are needed to use it. If the default configuration suits your application, no setup is even required. You will be able to use the module straight out of the box as a UART cable wireless replacement.

 

The EGBT04S can be mounted and pins soldered on a 24-pin hirel socket to form a breadboard friendly module.

 

 

 

 

 

 

But of course, hobbyists are a playful lot. They love features, and most would not mind a few steps of device setup (it is not terribly hard anyway). So we are eyeing the model that can be configured to work either as a master or a slave. A master Bluetooth device is probably needed if you want your device to connect to another Bluetooth device other than a PC.

 

Meanwhile, let’s take a quick look at the EGBT04S. This module measures only about 13×27.5mm. Its terminal layout is not exactly breadboard friendly – 1.5mm pitch pcb edge terminals type. Fortunately, only a few pins are actually needed to connect it to a UART circuit, and these pins are comfortably spread out. This, in combination of its just- about-the-right-size, allowed it to be soldered on a 24-pin hi-rel type IC socket. Now we have a breadboard friendly Bluetooth module!

 

We are waiting for the delivery of the final product. Once it arrives, we will describe in greater details how we can use it in our application circuits.