Notes on learning to implement Bluetooth communication

• Early project used HC-05, 06 BT modules to enable communication between 2 Arduinos (Tele-op Omni-Car)

• My goal now is to implement BT to enable PS-4 gamepad to talk to Picobot

Get some experience by following Pico BT example, under Pico MicroPython Examples.

• Followed the Instructions at Chapter 6: Working with Bluetooth in MicroPython
  • Installed ble_advertising.py and ble_temp_sensor.py on Pico #5.
  • Started ble_temp_sensor.py.
  • Producing this output in thonny:

  Sensor name Pico 28:CD:C1:0B:30:D2
  write temp 28.45 degc
  write temp 28.45 degc
  write temp 27.51 degc
  write temp 27.98 degc
  write temp 27.98 degc
  write temp 27.98 degc
  

  • This BT device didn't show up at all in my phone.
  • It did show up on my laptop but failed to pair, after which it would no longer show up.
  • I could stop ble_temp_sensor.py and restart it and it would again show up on my laptop.
  • This is as far as I got...

Got a pair of Pico W devices sending & receiving via Bluetooth

• Followed this tutorial Getting to grips with Bluetooth on Pico W to get both the server and client devices working.
  • server code
  • client code

This project implements Kevin McAleer's tutorial on Bluetooth Remote Controlled Robot which shows the use of aioble module to allow BT to work asynchronously.

• Kevin's tutorial shows using Bluetooth to connect a remote control (Pimoroni LCD screen wuth buttons) to his Burgerbot
• The server on Kevin's project imports pimoroni.py module which I chased down at the Pimoroni website
• The client code needs burgerbot.py module which I found at Kevin McAleer's Burgerbot repo
  • burgerbot.py needs motor and servo, which I wasn't able to find.
    • No matter... I'm not using burgerbot anyway.
• My project (below) uses a different LCD but aims to copy the Pico-to-Pico BLE communication exactly the same

My Remote (bluetooth server)

• Instead of using the Pimoroni display, I am using the Pico LCD 1.14
• Revised remote.py to my_remote.py to use the Pico LCD 1.14 device instead of the Pimoroni one.

My Robot (bluetooth client)

• Revised robot.py to not import burgerbot

Results

• Works great! Here is the output of the remote process:

>>> %Run -c $EDITOR_CONTENT
registering services
peripheral task started
blink task started
not connected
not connected
not connected
not connected
Connection from Device(ADDR_PUBLIC, 28:cd:c1:0a:4a:e2, CONNECTED)
connected: True
A
A
B
B
CTRL
CTRL
UP
UP
DOWN
DOWN
LEFT
LEFT
RIGHT
RIGHT

• But it crashes (after about a minute):

Traceback (most recent call last):
  File "<stdin>", line 239, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 237, in main
  File "uasyncio/funcs.py", line 1, in gather
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 215, in peripheral_task
  File "aioble/device.py", line 295, in __aexit__
  File "aioble/device.py", line 216, in disconnect
  File "aioble/device.py", line 232, in disconnected
  File "aioble/device.py", line 232, in disconnected
  File "uasyncio/core.py", line 1, in run_until_complete
  File "aioble/device.py", line 198, in device_task
  File "uasyncio/event.py", line 1, in wait
CancelledError: 
>>> 

• Meanwhile, this is the output of the robot process (on a subsequent run):

>>> %Run -c $EDITOR_CONTENT
blink task started
blink task stopped
starting peripheral task
Robot Remote not found
blink task started
blink task stopped
starting peripheral task
Found KevsRobots
UUID(0x1848)
Found Robot Remote Service
Connecting to Device(ADDR_PUBLIC, 28:cd:c1:0a:4c:25)
Connected
A button pressed
A button pressed
B button pressed
B button pressed
CNTR button pressed
CNTR button pressed
UP button pressed
UP button pressed
DOWN button pressed
DOWN button pressed
LEFT button pressed
LEFT button pressed
RIGHT button pressed
RIGHT button pressed

• Until the crash:

something went wrong; 
disconnected
blink task started
blink task stopped
starting peripheral task
Found KevsRobots
UUID(0x1848)
Found Robot Remote Service
Connecting to Device(ADDR_PUBLIC, 28:cd:c1:0a:4c:25)
Connected

Efforts to resolve crashing issue

• Posted a comment on Kevin's Youtube channel
• I noticed that another person posted a comment (~ 1 month ago) reporting a GattError after ~ 1 minute.
• I uploaded the Pimoroni micropython version 1.20.4 (to replace the Paspberry Pi version) but this didn't solve the problem.
  • However it answered my question about where to find the missing modules (pimoroni, motor, servo). They are included in this version of micropython.

MicroPython 856e08b1931b88271816a2f60648f6ff332235b2, picow v1.20.4 on 2023-08-04; Raspberry Pi Pico W with RP2040
Type "help()" for more information.
>>> help("modules")
__main__          breakout_dotmatrix                  gc                pimoroni_bus
_boot             breakout_encoder  gfx_pack          pimoroni_i2c
_boot_fat         breakout_encoder_wheel              hashlib           plasma
_onewire          breakout_icp10125 heapq             pngdec
_rp2              breakout_ioexpander                 hub75             qrcode
_thread           breakout_ltr559   interstate75      random
_uasyncio         breakout_matrix11x7                 inventor          re
_webrepl          breakout_mics6814 io                rp2
adcfft            breakout_msa301   jpegdec           select
aioble/__init__   breakout_paa5100  json              servo
aioble/central    breakout_pmw3901  lwip              socket
aioble/client     breakout_potentiometer              machine           ssl
aioble/core       breakout_rgbmatrix5x5               math              struct
aioble/device     breakout_rtc      micropython       sys
aioble/l2cap      breakout_scd41    mip/__init__      time
aioble/peripheral breakout_sgp30    motor             uasyncio/__init__
aioble/security   breakout_trackball                  neopixel          uasyncio/core
aioble/server     breakout_vl53l5cx network           uasyncio/event
array             builtins          ntptime           uasyncio/funcs
automation        cmath             onewire           uasyncio/lock
binascii          collections       os                uasyncio/stream
bluetooth         cppmem            pcf85063a         uctypes
boot              cryptolib         picoexplorer      urequests
breakout_as7262   dht               picographics      version
breakout_bh1745   ds18x20           picokeypad        webrepl
breakout_bme280   encoder           picoscroll        webrepl_setup
breakout_bme68x   errno             picounicorn       websocket
breakout_bmp280   framebuf          pimoroni          zlib
Plus any modules on the filesystem
>>> 

Time passes... Haven't figured out what is causing the code to crash

Decided to try approaching this from a new direction. Try to find another aioble server/client example that doesn't crash.

MicroPython aioble library GitHub repo has a temperature sensor / client example which I will now try out.

• That works fine too, for about a minute. Then I get this error:

Connecting to Device(ADDR_PUBLIC, 28:cd:c1:0a:4c:25)
Temperature: 24.53
Temperature: 24.79
Temperature: 24.77
Temperature: 24.53
Temperature: 24.93
Temperature: 25.37
Temperature: 24.92
Temperature: 24.98
Temperature: 25.12
Temperature: 25.16
Temperature: 25.16
Temperature: 24.80
Temperature: 24.52
Temperature: 24.22
Temperature: 24.36
Temperature: 24.32
Temperature: 24.08
Temperature: 23.89
Temperature: 24.46
Temperature: 24.94
Temperature: 25.23
Temperature: 25.12
Temperature: 24.65
Temperature: 24.77
Temperature: 24.61
Temperature: 24.90
Temperature: 24.55
Temperature: 24.45
Temperature: 24.69
Temperature: 24.79
Temperature: 24.80
Temperature: 24.73
Temperature: 24.49
Temperature: 24.70
Temperature: 24.07
Temperature: 24.24
Temperature: 23.96
Temperature: 24.14
Temperature: 24.54
Temperature: 24.13
Temperature: 24.12
Temperature: 24.46
Temperature: 24.19
Temperature: 24.36
Temperature: 24.28
Temperature: 24.40
Temperature: 24.44
Temperature: 24.57
Temperature: 24.89
Temperature: 24.93
Temperature: 25.04
Temperature: 24.56
Temperature: 24.32
Traceback (most recent call last):
  File "<stdin>", line 63, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 58, in main
  File "aioble/client.py", line 258, in read
GattError: 31

• Without disturbing the sensor (server), I restarted the client, which then continued without errors, but the value of the temperature was no longer changing.

Connecting to Device(ADDR_PUBLIC, 28:cd:c1:0a:4c:25)
Temperature: 24.16
Temperature: 24.16
Temperature: 24.16
...

• From this it looks like the ble client was continuing to get temperature data but the server was no longer sending fresh data.
• Moved the server to run under Thonny.
  • First start the server.
  • Then started the client.
  • Exactly 1 minute after the client connects, the server crashes with this traceback:

Connection from Device(ADDR_PUBLIC, 28:cd:c1:0a:4a:e2, CONNECTED)
Traceback (most recent call last):
  File "<stdin>", line 68, in <module>
  File "uasyncio/core.py", line 1, in run
  File "uasyncio/core.py", line 1, in run_until_complete
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 65, in main
  File "uasyncio/funcs.py", line 1, in gather
  File "uasyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 58, in peripheral_task
  File "aioble/device.py", line 295, in __aexit__
  File "aioble/device.py", line 216, in disconnect
  File "aioble/device.py", line 232, in disconnected
  File "aioble/device.py", line 232, in disconnected
  File "uasyncio/core.py", line 1, in run_until_complete
  File "aioble/device.py", line 198, in device_task
  File "uasyncio/event.py", line 1, in wait
CancelledError: 

I think I may have found the cause of the problem.

• Edited server code: last line in coroutine async def peripheral task():

  • originally was: await connection.disconnected()
  • after editing: await connection.disconnected(timeout_ms=None)

• Apparently, the default value is 60_000 (60 sec).

• Indeed the code for device.py in the aioble library module has a DeviceConnection class which has a coroutine async def disconnected(self, timeout_ms=60000, disconnect=False)

• Next I want to see if this will fix the problem with Kevin McAleer's code.

  • Yep, that seems to fix the problem. Now the code runs indefinitely.