Bluetooth (module) hardware question...

Hey guys..

We've all seen the Bluetooth modules for cheap on ebay/store fronts..etc..

(specifically the HC-5 & HC-06 modules)

HC-05: Master/Slave

HC-06: Slave

usually these come either plain-jane, like in the link above..

or with a 'base board' (like this)


My question is..

1.) besides having a head on it..for easy connection/breadboard friendly... what does the BASE board provide? * (I understand the pin spacing on the main board is odd/not breadboard friendly..etc)

2.) I see the BASE board has more components on it too? resistors, caps, an led? and either vRegulator or transistor..?.. and maybe a diode?

I guess Im not clear what the base board adds/offers?

leds flashing to show data transfer?

From what I gather.. these BT boards operate at +3.3v logic level.. but I dont see any level shifter on board.. (nor voltage divider)

Can I just solder directly to the base board.. or possibly just EMBED this whole HC-05/6 MAIN board into/onto another PCB?

(ie: design a circuit/pcb that has an area where the whole HC-05/6 board is re-flowed into it during assembly?)


Hello !

Your first link is what i use, recently there was a post where this one is mentioned (

The second does about the same as far as i can gather, however: it is NOT breadboard friendly. It has a small pitch and wires have to be soldered on the edges of the board. I have one of those as well, but I use the first one because it's more convenient.

Third same as the second

The fourth is just a pcb with some components, but without a bluetooth chip, hence the low price

The fifth: I can't place it, but I guess also without bluetooth chip, but there is no specification nor is there a picture of the top side

Six: pretty much number one again

Yes there are some extra components on the chip, the JY-MCU has a flashing led to give some sort of indication what it is doing. When connected it stays on. When not connected flashing.

Many IC's have input voltage between XX and YY and will work with everything in between, even without voltage regulator. Atmega328P-PU will work between 1.8 V and 5.5 V


I think what you mean by BASE board is just a board with BT IC.

You can integrate the entire board in a pcb, with either breadboard like sockets (like the arduino has) or solder it on a PCB directly (number two will work, have seen that done)

Or design your own PCB for BT IC.



As you point out the BT module is a 3.3V device. There are different types of base board but most have a 3.3V regulator and/or a 3.3V pin to supply the correct voltage to the BT module. They mostly just use an in-line resistor to drop a 5V TTL serial feed to the RX pin and have no resistor on the TX pin as arduino will detect 3.3V as HIGH. They also have a status LED with limiting resistor and capacitor(s) for the 3.3V regulator. The master version of the back board will ideally have a pin to assert command mode on the BT module and a pin to allow the arduino to know if it's connected of not.


thanks.. so it only has/needs the voltage divider on the 1 pin? (nice)..

I'll have to check where those other pins are..(I think called the STATE & KEY pins?? at least called that on the base/breakout boards for these)

as long as I regulate my power..the only extras (as I see explained) are for:

leds/supporting resistor - indications voltage regulator/supporting components - power regulation

and not 'needed' (per se`)


I have attached a datasheet that holds true for the modules I have. Notice the different LED output pin position depending on the module being HC-05 or HC-06. I’m sure KEY is connected to pin 34 and STATE probably connects to both pin 23 and pin(s) 31/32 so the back board will work with both module types. The datasheet also gives connection diagrams for 3.3V & 5V MCU’s

EGBT-bluetooth-module.pdf (370 KB)

Casually looking at it, Riva, that looks like the best write up I've ever seen.

thanks for the link/pdf it will help alot!


what are the programmable I/O pins on the BT module used for? (HC-05 only I guess)

what are the programmable I/O pins on the BT module used for? (HC-05 only I guess)

I have never used them but I would assume you could connect simple devices like LED’s and switches. I have not seen a way you can directly control I/O pins on a receiver from a transmitter so any reading/writing of these I/O would have to happen from the attached MCU.