Bluetooth Scale in Python (Sinocare CK-793, ETEKCITY, likely others built on the same chipset)

output.log

root@raspberrypi:~# python3 scale.py XX:RE:DA:CT:ED:XX
Connected.
152g
444g
688g
726g
783g
853g
978g
1753g
1814g
1880g
2124g
2451g
2565g
2595g
2334g
2360g
173g
0g
0g
0g
^C
root@raspberrypi:~#

scale.py

import asyncio
import sys
from bleak import BleakClient
import bleak.exc


address = sys.argv[1]
char_uuid = "0000fff4-0000-1000-8000-00805f9b34fb"
first_connect = True

def callback(sender: int, data: bytearray):
    grams = int.from_bytes(data[3:5], byteorder="little")
    print(f"{grams}g")

async def run(address):
    async with BleakClient(address) as client:
        global first_connect
        if first_connect:
            print("Connected.")
            first_connect = False
        notify = await client.start_notify(char_uuid, callback)

loop = asyncio.get_event_loop()
while(True):
    try:
        loop.run_until_complete(run(address))
    except bleak.exc.BleakDBusError:
        pass
    except KeyboardInterrupt:
        print()
        sys.exit(0)

Thanks to @hertzg for the info in https://github.com/hertzg/metekcity

@scoates You are very welcome :)

As an improvement you can also use the settled flag, which is set by the scale when the item weight has been stable.
With this you could show only the final weight or avoid weight spam after you have let go of the item.

https://github.com/hertzg/metekcity/tree/master/packages/esn00-packet#data-packet-weight-measurement-0xe0

Hi! Yep! My use case (which I didn't make clear) is that I'd like to use this scale for continuous measurement. The demo above is me putting my finger on the scale and increasing it over time. It also doesn't account for the sign. (-:

Yeah great job! Just happy that you found it useful. Cheers!

@scoates Am I right to assume that you will use the scale for profiling something? Like coffee, perhaps? I am looking for a Bluetooth scale that I can listen to preferably on the mobile side so that I can make a profiler app, but the code above is all Greek to me :) Do you know if this is possible for Sinocare CK-793 scale?

I actually switched my plans to use a custom piece built around a load cell and hx711, but it sounds to me like this would work for you, yeah. I used a ETEKCITY scale, but the Sinocare one should work, yep. Probably can't help too much with the basic coding, though.