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I have ordered my HC-05 BT modules. My question is this: Is it possible to send multiple channels over bluetooth. For example, stereo sound has two channels. I think i have seen people do this but i'm not sure.

If it is possible, could you please provide some more information on how its done? Thanks!

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The HC-03/05 are Bluetooth modules were designed for serial communication. Note that these implement the classic version of the Bluetooth stack, not the Low Energy 4.0+ version of the standard,

  • By using two complementary modules, one master and one slave, you will be able to pair them and connect two independent serial streams (full duplex), one stream in the direction master to slave and the other stream in the direction slave to master.

  • An alternative to the previous is connecting another device (for instance, a mobile or a PC bluetooth dongle) to one of these modules which will act as master/slave.

  • The AT command set available for these modules, as far as the documentation goes, does not allow multiplexing: sending multiple streams (more than one), simultaneously, in a certain direction (for instance, master to slave).

A possible solution is to do the multiplexing yourself in either end of the communication, not in the bluetooth module, but outside of it,

  • Let's say you connect a mobile application (running Android or iOS) with one of these modules. You could easily create your own message format for the serial communication, prepending an integer number which will indicate the number of channel.

A simplistic and very compact message format suitable for serial communications is the TLV (Type-Length-Value), which you may use for such an application,

http://en.wikipedia.org/wiki/Type-length-value

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  • \$\begingroup\$ Thanks a lot! The LE 3.0+ versions works the same way? I will have to create my own protocol so to speak? Or they can include multiple channels? If i do this, in the case of stereo, will i have phase problems, where the two signals are slightly out of phase instead of heard simultaneously? And BT streaming devices have their own protocol like you siad? \$\endgroup\$ – user1584421 Oct 25 '14 at 13:34
  • \$\begingroup\$ Bluetooth Low Energy is even worse (for your intended application), as you don't even have a serial communication profile to start with. Everything is designed to be very low power... You can only "send" small packets of information (characteristic values) of 1-20/22 bytes long. BT streaming devices are designed in two flavours: or with their own protocol (when the two interconnecting devices are designed by the same company) or with a standard Advanced Audio Distribution Profile (A2DP), the last one allowing maximum 2 channels (stereo). en.wikipedia.org/wiki/List_of_Bluetooth_profiles \$\endgroup\$ – jose.angel.jimenez Oct 26 '14 at 12:32

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