B4R Question Blue tooth master and slave

hatzisn

Well-Known Member
Licensed User
Hi everyone,

Could somebody clarify me something? Let's say I have a blue tooth device and I search for available devices in my phone after I set the BT device on. I find the device and I connect to it. Is my phone considered slave and the BT device master or the opposite?

Thanks in advance
 

emexes

Well-Known Member
Licensed User
If it is Bluetooth Low Energy, then the external device that is providing sensor data or actuator capability is the server, and the phone that is receiving data or issuing actuator commands is the client.

I would expect it is mostly the same for normal Bluetooth.

But usually the phone can be made to act as a server too, eg to emulate a Bluetooth GPS dongle or printer.

I don't know what the situation is when multiple phones are communicating with each other eg the demo chat app. I would expect that the first, initiating phone would be the master by default, and the other phone participants be slaves, but you'd have to look at the code to confirm that.
 

hatzisn

Well-Known Member
Licensed User
I ask because I am thinking of buying a blue tooth board to connect it with a meteorological blue tooth station in order for the bt board to communicate with it. I read in the forum that HC05 can be set either as a slave or a master with at command but the HC06 can be set only as as a slave. I am balancing thus between the two choices until I find out which is the correct. Further more the station indicates that it is compatible only with Android and not iPhone and this forces me to think that it is not ble compatible which points to HC05. What a mind job...
 
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emexes

Well-Known Member
Licensed User
A few quick questions, to make sure I haven't made any incorrect assumptions (surely not... ;-)
to connect it with a meteorological blue tooth station
# Do you already have the meteorological station?

# Does it already have a bluetooth interface installed?

If so,

## do you have their app communicating with the station?

## does the station show up in a general BLE app eg nRF Connect?
HC05 can be set either as a slave or a master with at command but the HC06 can be set only as as a slave.
The top hit Google result was to a master who has written other excellent stuff on the subject - it cheered me up to see his name.
http://www.martyncurrey.com/hc-05-and-hc-06-zs-040-bluetooth-modules-first-look/
This post suggests that the HC-06 is a cut-down (eg lower cost, or simpler) derivative of the HC-05. Perhaps the HC-05 was first, and they realised that 90% of them were only used as a plain serial link, and all the other features were just getting in the way.
I am balancing thus between the two choices until I find out which is the correct.
Get a HC-05. Worst case is that you might pay an extra $1 for features you don't use. Clinching argument: it wins the Ebay popularity test: 125 to 83 listings.

edit: I realised later that the two choices might be Bluetooth SPP and Bluetooth BLE, not HC-05 and HC-06... so perhaps hold off ordering until we've confirmed which type of Bluetooth it is.
Further more the station indicates that it is compatible only with Android and not iPhone and this forces me to think that it is not ble compatible which points to HC05. What a mind job...
Agreed (points to not BLE) and agreed (a mind job ;-).
 
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