# Make two bluetooth modules communicate directly?

Can one buy two cheap (and identical) bluetooth chips and make them talk to each other without needing a PC or a mobile phone?

I'm guessing the answer is a basic 'NO', but I might as well ask.

i.e.: I want to design a PCB and make a number of copies that can talk to each other, but also to a PC or mobile app.

Bluetooth still seems good for the device to app case, but when you take the mobile or the PC away, can you leave it with the devices paired to each other and not require the mobile to host it?

Can this be scaled further to make a basic network of bluetooth. ie: if i put 5 of these one of them pair to all the others? I don't have very high bandwidth requirements.

Like I said, probably not, but it is called "pairing", which I feel implies that the devices are equal somehow. So, what exactly is in the mobile phone or PC or bluetooth dongle that makes it different from a bluetooth device?

Also, if it just so happens that one can recommend a module, I would be really great to be able to get it for under USD$10 each at volumes. : ) - Any reason you are set on bluetooth? For low bandwidth hobby projects there are potentially much cheaper transceivers to use such as the nRF24L01+ which can be bought on ebay from chinese sellers for about$1 per. And they already have breakout boards and crystals etc. –  NickHalden May 16 '13 at 16:14

yes, there are many bluetooth modules with serial (TTL) interfaces, some even have built-in MCUs for user applications which you can use as a standalone module without a micro. However, I don't think you can find anything that cheap, the cheapest one I know of is the Roving Networks RN-42. with trace antenna.

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You seem to have a good sense of how things work but lack some basic knowledge about Bluetooth. You certainly don't need a PC to have a Bluetooth network. What you need is at least one device can operate at master mode. You can find some Bluetooth devices from ebay for 10 bucks.

However, if you are trying to build a self organizing network (where nodes can move and come and go) over Bluetooth, there are some challenges:

1. How to elect a master if a previous master has disappeared?
2. If nodes are scattered in such a way that some nodes are not in each others coverage, how to route your message?

Basically the major challenges is in software and algorithm. Fortunately, you can find these topics in most network/advanced network/wireless network textbooks.

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Thanks. It would be a static network actually. No moving devices. However I found (on wikipeida): A master Bluetooth device can communicate with a maximum of seven devices in a piconet. That could be quite useful for people to know. –  SpiRail May 18 '13 at 12:05