CODEWITHSUNDEEP
pythonbluetoothraspberry-pi
Ganesh
Ganesh

Reputation: 21

How to communicate between two raspberry pi via Bluetooth and send sensor data from one pi to another?

I'm working for some school project. I want to send temperature sensor data from one raspberry pi 4 to another pi 4 via Bluetooth. I searched a lot for tutorial but I didn't find any related tutorial. Please anyone help with this or any suggestions would be very helpful.

Upvotes: 1

Views: 5191

Answers (1)

Mark Setchell
Mark Setchell

Reputation: 207798

I know very little about Bluetooth and this answer may be dated or poor practice, but at least it works. If anyone knows better, please provide a better answer and I will delete this.

So, I have two Raspberry Pi 4 running Raspbian. I installed BlueDot on both with:

sudo pip3 install bluedot

I then paired them, running this on the first:

sudo bluetoothctl
[bluetooth]# discoverable on
[bluetooth]# pairable on
[bluetooth]# agent on
[bluetooth]# default-agent

and this on the second:

sudo bluetoothctl
[bluetooth]# discoverable on
[bluetooth]# pairable on
[bluetooth]# agent on
[bluetooth]# default-agent
[bluetooth]# scan on

When the first RasPi (hostname=pi4) showed up, I paired with it by typing this in the second RasPi:

[bluetooth]# pair DC:A6:32:03:0C:1B

Then I quit bluetoothctl on both.

Then I ran this server code (attributable to here) on the first RasPi UNDER sudo:

#!/usr/bin/env python3

from bluedot.btcomm import BluetoothServer
from time import sleep
from signal import pause

def data_received(data):
    print("recv - {}".format(data))
    server.send(data)

def client_connected():
    print("client connected")

def client_disconnected():
    print("client disconnected")

print("init")
server = BluetoothServer(
    data_received,
    auto_start = False,
    when_client_connects = client_connected,
    when_client_disconnects = client_disconnected)

print("starting")
server.start()
print(server.server_address)
print("waiting for connection")

try:
    pause()
except KeyboardInterrupt as e:
    print("cancelled by user")
finally:
    print("stopping")
    server.stop()
print("stopped")

And this code (attributable to here) on the second, also under sudo:

#!/usr/bin/env python3

from bluedot.btcomm import BluetoothClient
from datetime import datetime
from time import sleep
from signal import pause

def data_received(data):
    print("recv - {}".format(data))

print("Connecting")
c = BluetoothClient("pi4", data_received)

print("Sending")
try:
    while True:
        c.send("hi {} \n".format(str(datetime.now())))
        sleep(1)
finally:
    c.disconnect()

The two RasPis swapped messages successfully till interrupted. I measured the Round Trip Time (RTT) and it averaged around 30ms between two RasPi 4 placed around a metre apart.

It may be better to add the pi user to the dialout Linux group (or some other one) rather than run under sudo. If anyone knows, please say.

Upvotes: 5

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