Basic Bluetooth usage

[MrTinkerman]

Hi all,

I would like to know if I could use Bluetooth for my project. Currently I have Xiao nRF52840 sense boards (I need the IMU on these) that are connected to LoRa RFM95 modules. I got everything working like it should.

However, I would like to try using Bluetooth on the nRF's. Bluetooth is totally new to me and I hope someone can tell me if what I'm thinking of is even possible using ubluepy.

The messages I send are byte arrays, max ~16 bytes long (see this topic: https://github.com/orgs/micropython/discussions/16533)
Now i found this page: https://pybricks.com/project/micropython-ble-communication/
They use advertisement packets to transfer data without the need to establish a connection.

Sorry if I sound like a total n00b here but if anyone could tell me if this is even possible with ubluepy, that would be a great help.

In the meantime I'll explore the examples (https://github.com/micropython/micropython/tree/master/ports/nrf/examples)
and read up on what Bluetooth is all about.

Thanks for reading!

[jkorte-dev]

the nrf port has a bluetooth implementation which differs from all other ports, therefore most examples for ble will not work. but there is a pr from @andrewleech bringing the standard bluetooth api to the nrf port. I used it in one of my projects and made good experiences.

[MrTinkerman]

Well, it feels a little like abusing the code, but based on the example code for:
ubluepy_eddystone.py and ubluepy_scan.py
I hacked some code together that sends my 16 byte payload in an advertisement.

At the moment it feels like DIY 'Homer Simpson style' :)

Code for sending:

from ubluepy import Peripheral
from time import sleep_ms as sms

# Dummy packet / Data packet
dp = bytearray([2,1,6,3,3,170,254,23,							
                22,170,254,16,238,0])

p = Peripheral()

def send():
    
    dp.extend(bytearray([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]))
    dp.extend(bytearray(1))
    
    while 1:   
    
        p.advertise(data=dp)
        sms(250)
        p.advertise_stop()
        sms(1000)

send()

Code for receiving:

from ubluepy import Scanner
from time import ticks_ms as tms
from time import sleep_ms as sms

s = Scanner()
        
while 1:
    
    scan_rslt = s.scan(1000)
    
    for e in scan_rslt:
        
        sd = e.getScanData()
        
        if len(sd):
            
            try:
                ft, st, tt = sd[0], sd[1], sd[2]

                if (   ft[0] == 1
                   and ft[1] == 'AD_TYPE_FLAGS'
                   and ft[2] == b'\x06'
                   and st[0] == 3
                   and st[1] == 'AD_TYPE_16BIT_SERVICE_UUID_COMPLETE'
                   and st[2] == b'\xaa\xfe'
                   and tt[0] == 22
                   and tt[1] == 'AD_TYPE_SERVICE_DATA'):
                    
                    payload = tt[2][5:-1]
                    print(f'{tms()}   {payload}')
            except:
                pass

[jkorte-dev]

I didn’t even try the low level API. Thank you for sharing.

[DavesCodeMusings]

This may not be exactly what you're looking for, but I saw "BLE" and "data in advertising packet" and I perked up.

Recently, I got it in my head to send temperature/humidity readings in a BLE advertising packet. I'm using an ESP32 as the sender and Home Assistant as the receiver, but the idea is similar I think. I have the code on GitHub:

https://github.com/DavesCodeMusings/BLESP32/

I found MicroPython's aioble library pretty easy to use. I don't think I have any platform specific stuff in the code (other than a debug message showing the ESP32 Bluetooth MAC.) I think if you replace the read_sensor() function with the code to read your own sensor, you should be good to go. You can rip out the GATT characteristics code as it has no bearing on the advertising packet. Or you can change the characteristic to match what you're measuring.