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Topic: Team radio chat project advice (Read 152 times) previous topic - next topic

Marcang

Nov 10, 2019, 04:27 pm Last Edit: Nov 10, 2019, 04:28 pm by Marcang
Hi all,

I'm Marc from Italy, this is my first post here. With some friends we're planning to develop a system that permits to communicate wirelessly between multiple devices, but we need some advice :)

This should be possible where no WiFi or GSM is available, so we were thinking of RF modules, the range should be able to reach around 1.5 - 2 Km, also trees and buildings on the way may not be excluded.
Another important feature of this project is to avoid interference, so some sort of unique device ID that let's communicate two groups of devices in a completely separate way, an example to clarify:

group1: id1, id2, id3 - should be able to chat between them, but not with a device of group2

group2: id4, id5, id6 - should be able to chat between them, but not with a device of group1

The device will only have a display to show incoming messages, but to write them we're thinking of using our smartphones, connected via usb or bluetooth to Arduino.

What kind of Arduino board and RF module do you suggest that will do for us?

zwieblum


srnet

#2
Nov 10, 2019, 06:20 pm Last Edit: Nov 10, 2019, 06:21 pm by srnet
Its not completly clear what you are trying to do, but the part about incoming messages and writing them suggests you talling about sending text messages.

I guess the question is why ?

The mobile phones you have will do this all just fine on their own.

LoRa is probably the only independant wirelss sytem that would give the range, given the legal restrictions on radio devices and powers etc.
http://www.50dollarsat.info/
http://www.loratracker.uk/

johnwasser

The mobile phones you have will do this all just fine on their own.
Not without a GSM or WiFi network available.
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srnet

Not without a GSM or WiFi network available.
Yes of course, and you have highlighted may lack of reading of posts.
http://www.50dollarsat.info/
http://www.loratracker.uk/

srnet

Another important feature of this project is to avoid interference, so some sort of unique device ID that let's communicate two groups of devices in a completely separate way, an example to clarify:
Interesting, so why exactly is this a requirement, what is the exact purpose of the project ?

A much fuller explanation of what you are attempting to do will lead to far better answers to your questions.
http://www.50dollarsat.info/
http://www.loratracker.uk/

johnwasser

If by "interference" you mean having your messages read by the other team...  Just use some simple encryption.  Each team has an encryption key they share only among themselves.  Each message has a team ID.  If someone tries to read a different team's messages they will just get the encrypted version.

The key can be as simple as a 32-bit number passed to randomseed();  For extra security you can pass a 32-bit "salt" value in the message header.  XOR the salt with the key and pass the result to randomseed().  Then you XOR each byte of the message with the next value from random(256).

Only if the other team can determine the 32-bit key can they read the messages and there are over 4 billion possibilities.
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TomGeorge

#7
Nov 11, 2019, 06:59 am Last Edit: Nov 11, 2019, 07:02 am by TomGeorge
Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .

Can you tell us your electronics, programming, arduino, hardware experience?

These links may help;

https://hackaday.io/project/164242-skrypt

https://www.hackster.io/news/build-your-own-mini-walkie-talkie-with-electronictricks-snaponair-pcb-3c035bfd7cb8

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

Marcang

Woah! Thanks to everyone for their answer! Let me try to reply to each question..
What we are trying to achieve is a way to communicate privately via text messages between a restricted number of users, where more often than not mobile phones networks don't work very well.. It's for a sort of a stealth game that we invented and are playing among us, imagine something similar to Airsoft, without guns, but with some targets that every team has to achieve, and silence falls within the rules (so no walkie-talkie). I know, it sounds more weird than it really is, but this is what you wanted to hear :)

Regarding my background, I have more than basic knowledge of electronics (I studied it at school, I can solder and I keep enjoying it at home when I have to modify or repair some electronic circuit of any kind).  First time experience with Arduino, before diving ourself in this project we wanted to know if it is feasible, and it seems it is.

The two projects posted seem very interesting indeed!

If by "interference" you mean having your messages read by the other team...  Just use some simple encryption.  Each team has an encryption key they share only among themselves.  Each message has a team ID.  If someone tries to read a different team's messages they will just get the encrypted version.

Yes, you got the point. Also, each team, should not be allowed to send "fake" messages to the other one as well, and it's important that messages are not received by error by the wrong team. But I think that this can be implemented with some kind of setting for LoRa (by the way, I looked and it seems it's the right module for this project as you all suggested). I have not studied it yet, maybe there's something similar to addresses and pipes of nfr24l01, combining multiple devices and limiting communication (sending and receiving) only between them.

srnet

But I think that this can be implemented with some kind of setting for LoRa (by the way, I looked and it seems it's the right module for this project as you all suggested).
I am not so sure, and I have spent a lifetime testing LoRa and carrying out link tests with it.

This bit was important;

"The range should be able to reach around 1.5 - 2 Km, also trees and buildings on the way may not be excluded"

If by that you mean in urban areas, then I dont see, given what you have said so far that LoRa woould go much beyond 1km.
http://www.50dollarsat.info/
http://www.loratracker.uk/

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