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I have a bluetooth-enabled clock from Amazon that I want to control with python (using bleak). I've connected to it without any problems and logged all the services/characteristics (see below).

The clock also has a (very bad) iOS app. I've used xcode and packet logger to try to figure out what buttons in the app correspond to what handles and values (also below). But the handles from the log don't match any numbers in the list of services, and when I try to reproduce the same actions from python, I get an error, eg:

  File "C:\Users\zacha\anaconda3\lib\site-packages\bleak\backends\winrt\client.py", line 600, in write_gatt_char
    raise BleakError("Characteristic {} was not found!".format(char_specifier))
bleak.exc.BleakError: Characteristic 31 was not found!

Am I not interpreting the logs correctly? Or is there information exchanged when a device first connects that affects what services are exposed? New to working with Bluetooth, any help appreciated. I can edit to add the pairing logs from iOS if necessary.

My code:

import sys
import platform
import asyncio
import logging

from bleak import BleakClient
from bleak import BleakScanner

# these are the write values associated with inputs, as logged from iOS
hex_power = "1F30 4145 09"
hex_reset = "1F30 414F 09"
hex_start = "1F30 4151 09"
hex_stop = "1F30 4150 09"

ba_power = bytes.fromhex(hex_power)
ba_reset = bytes.fromhex(hex_reset)
ba_start = bytes.fromhex(hex_start)
ba_stop = bytes.fromhex(hex_stop)

TIMER_NAME = "GxTimer_31A0"
address = "BA:03:C4:2F:31:A0"

async def discover():
    devices = await BleakScanner.discover()
    for d in devices:
        if d.name == TIMER_NAME:
            print("Timer Found")
            for property, value in vars(d).items():
                print(property, ':', value)
            address = d.address

async def main(address):
    async with BleakClient(address) as client:
        print("Pairing...")
        paired = await client.pair()
        print(paired)

        await client.write_gatt_char(73, ba_power)

asyncio.run(discover())
asyncio.run(main(address))

Typical log from xcode / iOS of an action I'd like to replicate:

Feb 02 19:28:34.192  ATT Send         0x0052  00:00:00:00:00:00  Write Command - Handle:0x001F - Value: 1F30 4145 09  

    Write Command - Handle:0x001F - Value: 1F30 4145 09

    Opcode: 0x0052

    Attribute Handle: 0x001F (31)

    Value: 1F30 4145 09

And services list for the device (comments are mine):

# device info
INFO:root:[Service] 00001800-0000-1000-8000-00805f9b34fb (Handle: 1): Generic Access Profile
DEBUG:bleak.backends.winrt.client:Read Characteristic 0002 : bytearray(b'GxTimer_31A0')
INFO:root:      [Characteristic] 00002a00-0000-1000-8000-00805f9b34fb (Handle: 2):  (read), Value: b'GxTimer_31A0'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0004 : bytearray(b'\x00\x00')
INFO:root:      [Characteristic] 00002a01-0000-1000-8000-00805f9b34fb (Handle: 4):  (read), Value: b'\x00\x00'

# indicate only
INFO:root:[Service] 00001801-0000-1000-8000-00805f9b34fb (Handle: 12): Generic Attribute Profile
INFO:root:      [Characteristic] 00002a05-0000-1000-8000-00805f9b34fb (Handle: 13):  (indicate), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 000F : bytearray(b'\x02\x00')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 15): Client Characteristic Configuration) | Value: b'\x02\x00'

# device info
INFO:root:[Service] 0000180a-0000-1000-8000-00805f9b34fb (Handle: 16): Device Information
DEBUG:bleak.backends.winrt.client:Read Characteristic 0011 : bytearray(b'\xba\x03\xc4\x00\x00/1\xa0')
INFO:root:      [Characteristic] 00490220-0147-7070-4121-01d002290078 (Handle: 17):  (read), Value: b'\xba\x03\xc4\x00\x00/1\xa0'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0013 : bytearray(b'Tv5.11u_20210115_EP\x00\x00')
INFO:root:      [Characteristic] 00002a26-0000-1000-8000-00805f9b34fb (Handle: 19):  (read), Value: b'Tv5.11u_20210115_EP\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0015 : bytearray(b'RSBRS02ABR\x00\x00')
INFO:root:      [Characteristic] 00002a27-0000-1000-8000-00805f9b34fb (Handle: 21):  (read), Value: b'RSBRS02ABR\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0017 : bytearray(b'RFstar\x00\x00')
INFO:root:      [Characteristic] 00002a29-0000-1000-8000-00805f9b34fb (Handle: 23):  (read), Value: b'RFstar\x00\x00'

# UART (data transmission?)
INFO:root:[Service] 6e400001-b5a3-f393-e0a9-e50e24dcca9e (Handle: 25): Nordic UART Service
INFO:root:      [Characteristic] 6e400003-b5a3-f393-e0a9-e50e24dcca9e (Handle: 26): RX CHAR (notify), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 001C : bytearray(b'RX CHAR\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 28): Characteristic User Description) | Value: b'RX CHAR\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 001D : bytearray(b'\x01X')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 29): Client Characteristic Configuration) | Value: b'\x01X'
INFO:root:      [Characteristic] 6e400002-b5a3-f393-e0a9-e50e24dcca9e (Handle: 30): TX CHAR (write-without-response,write), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0020 : bytearray(b'TX CHAR\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 32): Characteristic User Description) | Value: b'TX CHAR\x00'

# password stuff
INFO:root:[Service] 0000ffc0-0000-1000-8000-00805f9b34fb (Handle: 33): Vendor specific
INFO:root:      [Characteristic] 0000ffc1-0000-1000-8000-00805f9b34fb (Handle: 34): Password (write-without-response), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0024 : bytearray(b'Password\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 36): Characteristic User Description) | Value: b'Password\x00\x00'
INFO:root:      [Characteristic] 0000ffc2-0000-1000-8000-00805f9b34fb (Handle: 37): Password Set Event (notify), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0027 : bytearray(b'\x01a')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 39): Client Characteristic Configuration) | Value: b'\x01a'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0028 : bytearray(b'Password Set Event\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 40): Characteristic User Description) | Value: b'Password Set Event\x00\x00'

# more device info?
INFO:root:[Service] 0000ff90-0000-1000-8000-00805f9b34fb (Handle: 41): Vendor specific
DEBUG:bleak.backends.winrt.client:Read Characteristic 002A : bytearray(b'GxTimer_31A0')
INFO:root:      [Characteristic] 0000ff91-0000-1000-8000-00805f9b34fb (Handle: 42): Device Name (read,write-without-response,write), Value: b'GxTimer_31A0'
DEBUG:bleak.backends.winrt.client:Read Descriptor 002C : bytearray(b'Device Name\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 44): Characteristic User Description) | Value: b'Device Name\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 002D : bytearray(b'\x00')
INFO:root:      [Characteristic] 0000ff92-0000-1000-8000-00805f9b34fb (Handle: 45): Connect Interval (read,write-without-response,write), Value: b'\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 002F : bytearray(b'Connect Interval\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 47): Characteristic User Description) | Value: b'Connect Interval\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0030 : bytearray(b'\x01')
INFO:root:      [Characteristic] 0000ff93-0000-1000-8000-00805f9b34fb (Handle: 48): Uart BPS (read,write-without-response,write), Value: b'\x01'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0032 : bytearray(b'Uart BPS\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 50): Characteristic User Description) | Value: b'Uart BPS\x00\x00'
INFO:root:      [Characteristic] 0000ff94-0000-1000-8000-00805f9b34fb (Handle: 51): Soft Reset (write-without-response,write), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0035 : bytearray(b'Soft Reset\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 53): Characteristic User Description) | Value: b'Soft Reset\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0036 : bytearray(b'\x00')
INFO:root:      [Characteristic] 0000ff95-0000-1000-8000-00805f9b34fb (Handle: 54): Advert Period (read,write-without-response,write), Value: b'\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0038 : bytearray(b'Advert Period\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 56): Characteristic User Description) | Value: b'Advert Period\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0039 : bytearray(b'RS')
INFO:root:      [Characteristic] 0000ff96-0000-1000-8000-00805f9b34fb (Handle: 57): Product ID (read,write-without-response,write), Value: b'RS'
DEBUG:bleak.backends.winrt.client:Read Descriptor 003B : bytearray(b'Product ID\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 59): Characteristic User Description) | Value: b'Product ID\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 003C : bytearray(b'\x01')
INFO:root:      [Characteristic] 0000ff97-0000-1000-8000-00805f9b34fb (Handle: 60): Transmit Power Level (read,write-without-response,write), Value: b'\x01'
DEBUG:bleak.backends.winrt.client:Read Descriptor 003E : bytearray(b'Transmit Power Level\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 62): Characteristic User Description) | Value: b'Transmit Power Level\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 003F : bytearray(b'!\x03\xba\x03\xc4/1\xa0\x01\x05\x00\x01\x00\x00')
INFO:root:      [Characteristic] 0000ff98-0000-1000-8000-00805f9b34fb (Handle: 63): Advert Data Define (read,write-without-response,write), Value: b'!\x03\xba\x03\xc4/1\xa0\x01\x05\x00\x01\x00\x00'        
DEBUG:bleak.backends.winrt.client:Read Descriptor 0041 : bytearray(b'Advert Data Define\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 65): Characteristic User Description) | Value: b'Advert Data Define\x00\x00'

# input/output
INFO:root:[Service] 0000fff0-0000-1000-8000-00805f9b34fb (Handle: 66): Vendor specific
DEBUG:bleak.backends.winrt.client:Read Characteristic 0043 : bytearray(b'\x00')
INFO:root:      [Characteristic] 0000fff1-0000-1000-8000-00805f9b34fb (Handle: 67): Config for port (read,write-without-response,write), Value: b'\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0045 : bytearray(b'Config for port\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 69): Characteristic User Description) | Value: b'Config for port\x00\x00'
INFO:root:      [Characteristic] 0000fff2-0000-1000-8000-00805f9b34fb (Handle: 70): Output Bit (write-without-response,write), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0048 : bytearray(b'Output Bit\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 72): Characteristic User Description) | Value: b'Output Bit\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0049 : bytearray(b'\x00')
# this seems like the one vvv
INFO:root:      [Characteristic] 0000fff3-0000-1000-8000-00805f9b34fb (Handle: 73): Input Bit (read,notify), Value: b'\x00'
#
DEBUG:bleak.backends.winrt.client:Read Descriptor 004B : bytearray(b'Input Bit\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 75): Characteristic User Description) | Value: b'Input Bit\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 004C : bytearray(b'\x00n')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 76): Client Characteristic Configuration) | Value: b'\x00n'
DEBUG:bleak.backends.winrt.client:Read Characteristic 004D : bytearray(b'\x00\x00\x00\x00')

INFO:root:      [Characteristic] 0000fff4-0000-1000-8000-00805f9b34fb (Handle: 77): Delay1 for IO6 OverTurn (read,write-without-response,write), Value: b'\x00\x00\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 004F : bytearray(b'Delay1 for IO6 OverTurn\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 79): Characteristic User Description) | Value: b'Delay1 for IO6 OverTurn\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0050 : bytearray(b'\x00\x00\x00\x00')
INFO:root:      [Characteristic] 0000fff5-0000-1000-8000-00805f9b34fb (Handle: 80): Delay2 for IO6 OverTurn (read,write-without-response,write), Value: b'\x00\x00\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0052 : bytearray(b'Delay2 for IO6 OverTurn\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 82): Characteristic User Description) | Value: b'Delay2 for IO6 OverTurn\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0053 : bytearray(b'\x00\x00\x00\x00')
INFO:root:      [Characteristic] 0000fff6-0000-1000-8000-00805f9b34fb (Handle: 83): Delay1 for IO7 OverTurn (read,write-without-response,write), Value: b'\x00\x00\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0055 : bytearray(b'Delay1 for IO7 OverTurn\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 85): Characteristic User Description) | Value: b'Delay1 for IO7 OverTurn\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0056 : bytearray(b'\x00\x00\x00\x00')
INFO:root:      [Characteristic] 0000fff7-0000-1000-8000-00805f9b34fb (Handle: 86): Delay2 for IO7 OverTurn (read,write-without-response,write), Value: b'\x00\x00\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0058 : bytearray(b'Delay2 for IO7 OverTurn\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 88): Characteristic User Description) | Value: b'Delay2 for IO7 OverTurn\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0059 : bytearray(b'\x00\x00\x00\x00')
INFO:root:      [Characteristic] 0000fff8-0000-1000-8000-00805f9b34fb (Handle: 89): IO0 PULSE COUNT (read,notify), Value: b'\x00\x00\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 005B : bytearray(b'IO0 PULSE COUNT\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 91): Characteristic User Description) | Value: b'IO0 PULSE COUNT\x00\x00'

# ADC (analog to digital converter)
INFO:root:[Service] 0000ffd0-0000-1000-8000-00805f9b34fb (Handle: 92): Vendor specific
DEBUG:bleak.backends.winrt.client:Read Characteristic 005D : bytearray(b'\x00')
INFO:root:      [Characteristic] 0000ffd1-0000-1000-8000-00805f9b34fb (Handle: 93): Adc Switch (read,write-without-response,write), Value: b'\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 005F : bytearray(b'Adc Switch\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 95): Characteristic User Description) | Value: b'Adc Switch\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0060 : bytearray(b'\x01\xf4')
INFO:root:      [Characteristic] 0000ffd2-0000-1000-8000-00805f9b34fb (Handle: 96): Adc Period (read,write-without-response,write), Value: b'\x01\xf4'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0062 : bytearray(b'Adc Period\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 98): Characteristic User Description) | Value: b'Adc Period\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0063 : bytearray(b'\x00\x00')
INFO:root:      [Characteristic] 0000ffd3-0000-1000-8000-00805f9b34fb (Handle: 99): Adc Result (read,notify), Value: b'\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0065 : bytearray(b'Adc Result\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 101): Characteristic User Description) | Value: b'Adc Result\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0066 : bytearray(b'')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 102): Client Characteristic Configuration) | Value: b''

# pwm stuff
INFO:root:[Service] 0000ffb0-0000-1000-8000-00805f9b34fb (Handle: 103): Vendor specific
DEBUG:bleak.backends.winrt.client:Read Characteristic 0068 : bytearray(b'\x01')
INFO:root:      [Characteristic] 0000ffb1-0000-1000-8000-00805f9b34fb (Handle: 104): Pwm Config (read,write-without-response,write), Value: b'\x01'
DEBUG:bleak.backends.winrt.client:Read Descriptor 006A : bytearray(b'Pwm Config\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 106): Characteristic User Description) | Value: b'Pwm Config\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 006B : bytearray(b'\xff\xff')
INFO:root:      [Characteristic] 0000ffb2-0000-1000-8000-00805f9b34fb (Handle: 107): Pwm Out (read,write-without-response,write), Value: b'\xff\xff'
DEBUG:bleak.backends.winrt.client:Read Descriptor 006D : bytearray(b'Pwm Out\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 109): Characteristic User Description) | Value: b'Pwm Out\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 006E : bytearray(b'\x82\xff')
INFO:root:      [Characteristic] 0000ffb3-0000-1000-8000-00805f9b34fb (Handle: 110): Pwm Clk (read,write-without-response,write), Value: b'\x82\xff'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0070 : bytearray(b'Pwm Clk\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 112): Characteristic User Description) | Value: b'Pwm Clk\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Characteristic 0071 : bytearray(b'\x00\x00')
INFO:root:      [Characteristic] 0000ffb4-0000-1000-8000-00805f9b34fb (Handle: 113): Pwm Time (read,write-without-response,write), Value: b'\x00\x00'
DEBUG:bleak.backends.winrt.client:Read Descriptor 0073 : bytearray(b'Pwm Time\x00\x00')
INFO:root:              [Descriptor] 00002901-0000-1000-8000-00805f9b34fb (Handle: 115): Characteristic User Description) | Value: b'Pwm Time\x00\x00'


INFO:root:[Service] 0000fd00-0000-1000-8000-00805f9b34fb (Handle: 116): Vendor specific
INFO:root:      [Characteristic] 0000fd01-0000-1000-8000-00805f9b34fb (Handle: 117):  (write-without-response), Value: None
INFO:root:      [Characteristic] 0000fd02-0000-1000-8000-00805f9b34fb (Handle: 119):  (write-without-response,notify), Value: None
DEBUG:bleak.backends.winrt.client:Read Descriptor 0079 : bytearray(b'\x00\x00')
INFO:root:              [Descriptor] 00002902-0000-1000-8000-00805f9b34fb (Handle: 121): Client Characteristic Configuration) | Value: b'\x00\x00'
zchrywht
  • 51
  • 2
  • You should start by using a generic BLE scanner such as [nRF Connect](https://www.nordicsemi.com/Products/Development-tools/nrf-connect-for-mobile) to take a look at the available services and characteristics. You should be able to find the characteristics mentioned in your log by uuid and write data to it – Michael Kotzjan Feb 03 '22 at 06:00
  • As @MichaelKotzjan said, trying to write the values using `nRF Connect` first is a good first step. The `73` in the line `await client.write_gatt_char(73, ba_power)` looks wrong. I would expect it to look more like `await client.write_gatt_char('6e400002-b5a3-f393-e0a9-e50e24dcca9e', ba_power)` – ukBaz Feb 03 '22 at 13:46
  • 1
    Thanks! This worked. The problem was that I was trying to use handles rather than UUIDs. nRF connect made it easier to recognize what I was looking for though. – zchrywht Feb 03 '22 at 15:56

0 Answers0