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I have been developing an small project which requieres a communication between two Raspberries, the first one acts as a Beacon and the second one tries to connect to that beacon and obtain the RSSI and the small data that had been written into the channel.

The problem is that I have been trying to develope this arquitecture with python through the pygattlib library (https://bitbucket.org/OscarAcena/pygattlib/src/default/) which acts as a wrapper around the GATT protocol implementation of bluez.

This library works prefectly when you want to create a BLE and you want to connect from the other Raspberry, however, I cannot find any information on how to send data from the beacon itself to make the client read it.

Through the small tutorial that Adafruit teaches (https://learn.adafruit.com/introduction-to-bluetooth-low-energy/gatt) I can understand that the client needs to send a request, however when it comes to answer by the server, there is no information also from the library that helps about that.

I have been searching for other libraries with no result so I cannot procceed to the next steps of my project, but nevertheless I will continue searching for it.

Also I have been looking to make with the gattlib library (https://github.com/labapart/gattlib), but it does not appear hwo to create a BLE.

PD: Sorry for not posting code about the problem I thoguh It would not be require for this type of question. As the library which I used says, to create a beacon on the Raspberry server, you only need to asociate it to a interface and start advertising with a custon UUID

from gattlib import BeaconService
import time

service = BeaconService("hci0")

service.start_advertising("11111111-2222-3333-4444-555555555555",
            1, 1, 1, 200)
time.sleep(5)
service.stop_advertising()

print("Done.")

And when you want to read or write into the channel, the library provides you with an easy example (to read you would only need to replace self.requester.write_by_handle(0x2e, str(bytearray([2]))) for

data = self.requester.read_by_handle(0x1)[0]
        print("bytes received:", end=' ')
        for b in data:
            print(hex(ord(b)), end=' ')
        print("")

And use it in the next example loaded in the Raspberry Client

from __future__ import print_function

import sys
import time
from gattlib import GATTRequester, GATTResponse
from gattlib import BeaconService


class Writer(object):
    def __init__(self, address):
        self.requester = GATTRequester(address, False)
        self.connect()
        self.send_data()

    def connect(self):
        print("Connecting...", end=' ')
        sys.stdout.flush()

        self.requester.connect(True)
        print("OK!")

    def send_data(self):
        self.requester.write_by_handle(0x2e, str(bytearray([2])))

class Beacon(object):

    def __init__(self, data, address):
        self._uuid = data[0]
        self._major = data[1]
        self._minor = data[2]
        self._power = data[3]
        self._rssi = data[4]
        self._address = address

    def __str__(self):
        ret = "Beacon: address:{ADDR} uuid:{UUID} major:{MAJOR}"\
                " minor:{MINOR} txpower:{POWER} rssi:{RSSI}"\
                .format(ADDR=self._address, UUID=self._uuid, MAJOR=self._major,
                        MINOR=self._minor, POWER=self._power, RSSI=self._rssi)
        return ret

service = BeaconService("hci0")
devices = service.scan(2)

for address, data in list(devices.items()):
    b = Beacon(data, address)
    print(b)
    Writer(address)

print("Done.")

The point is, based on the documentation of that library, you can only read (sync and async) and write with a known address what in this case means that the beacon needs to know the address of the client and also make a connection to it which I think it's not possible because the only one that is emitting is the beacon.

  • You're probably going to have to post some minimal code to get a useful answer to this. – Brick Jun 4 at 17:15

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