Make Your own FREE Bluetooth Serial Module : PART 2

Hi,
This is continuation to my previous blog. In this post I will go through the steps of building the module itself and share some of my findings :)

NOTE : Unfortunately due to lack of a good camera with stand I haven't recorded the construction Process :(.

So, lets Go :) 
In my last post I had mentioned how to procure the IC and basic components you may need for constructing the module. I had also posted some reference images to follow. Hopefully by now you guys may have received the module  :) :)

Step 1  :   Preparation

 For the first step just grab everything required for the construction as listed in my last post  Here are some of the pics for the module I got from TI :) (Please mind my camera Nexus 4 isn't known for it's cam quality :P)

 

Step 2  : Getting  Power Signals soldered 

Firstly, apply flux to the entire pad array as shown in the picture below 

    

Then Solder the GND pins together. Further in the pictures below I have soldered the CTS pin to GND also, but I will recommend you guys to do it later once we are finished soldering the OP3 pin :)

Also connect the 32Khz + pin to GND as suggested by TI . 

Finally, solder the VCC signal, that is VCC+ V_Core as shown in the reference images in my previous post. Now we have the power supply up :) , At this point grab a multimeter and check for shorts between VCC and GND :)
 

Step 3  :  Soldering other Important signals

In order for us to work with the module, we must first get the UART Signals set up :), as well as the Baud Rate select pins selected. You can change the communication Baud rate by tweaking the pins OP3, OP4 and OP5 in the below fashion,(I have used 9600 Baud by default)

OP3	OP4	OP5	Function
1	0	1	UART speed 9.6 kbps
1	1	0	UART speed 115.2 kbps
1	1	1	UART speed 921.6 kbps

We will start by soldering 1K pull-up resistors to the respective OP3 and OP5 pins and will later connect them to the VCC pins.

Meanwhile also connect some long wires to the Rx and the Tx pins of the module.

 And some neat trick for connecting the resistors to VCC.

After successfully connecting the resistors, now is a good time to connect the CTS pin to ground :) 
Now our module is almost ready :) , to test : power on the module and check weather you get a "Serial Port Device" of some MAC Address in your Bluetooth scan list. If everything is fine, glue up the connections or simply add a double sided tape to firmly attach the wires hanging out :).


Step 4  :  Making the module 

We now will build the base of the module and make this a plug and play module :) .

First, we will choose the corner of a prototyping PCB. and align the module in such a way that the upper part of the module till the horizontal pins do not come in contact or is near to the prototyping PCB copper pads.(The upper section of the Module is the Antenna and we should have some antenna clearance or else the signal from the module may be week.) as shown in the bottom images.

Then we cut  the amount prototyping PCB required for us. Always cut a bit more than required for margins :)

then we insert the VCC, GND Rx and Tx, wires through the holes and solder them to the PCB. Meanwhile, also solder 4pin 90dig 0.1" standard headers and connect the header to the signals.

So, Our module is ready :) :D , I always forget what I do after couple of days :P  so it's always a good idea to label each pin with a permanent marker :). Finally I also like to hot glue things up as sometimes if the double sided tape gets off the it's a problem :( .

NOTE : Handel the module very carefully through Step 4. As the wires as well as the pads are delicate. It so happened for me that while going through Step 4, I somehow broke the OP3 Pad from the module and the entire module was done :( .

Step 5  : Testing the module 

Well the easiest way to test is connecting it with an MSP430 Launchpad/Arduino/etc. and just do a serialPrint(Receving). You can use my Bluebot Project code for the MSP430 Launchpad here which already has that done. Visit my LMX9838 Module interfacing with MSP430 Launchpad post for further interfacing here. 

Some Important Tips for Soldering and construction  

 

Tip 1 : Always apply flux to the pad and tin the pad before soldering a wire to it. 

Tip 2 : Always try and Short all the ground and power pins as few of them are sometimes regulator references and they are important to be connected to VCC. (Well check the datasheet for specific instructions)

Tip 3 : Always heat the pad a bit first before inserting the tin thread for better soldering (The Tin thread usually has flux on top of it which makes it easier that ways for sticking)

Tip 4 : Do Not HEAT the pad for larger duration as due to over heating, the pad may wear off/ or worst rip of :( - That happened to me so take care .

Tip 5 : Always tend to use single stand thin wires with coating or extracted copper wires with coating :) this saves loads of time and energy :)

Happy Hacking
Gurinder Singh Gill
technervers.com