freakone / BLE-scale-reader

BLE-scale-reader

Interact with the GOCLEVER BLE Kitchen Scale

• Read all properites from the device

Install $ npm install $ cordova run android

Hardware description

Scale has built in BLE transmitter with disabled connectivity. It only advertises itself without pairing or connection option. Characteristic parameters:

• Name: TJLSCALE
• Mac address: 28:32
• All measurements are stored in advertising informations sent by the device.

Protocol description was reverse-engineered basing on phone with Android 6.0. Main work pipeline will look like this:

• scan the BLE neighbour devices
• filter the list to scale-only-devices (prefferably basing on MAC address)
• read advertisement data and process it

Protocol description

From the byte array obtained from advertisement data important data are those from 8th field to the 13th field.

1	2	3	4	5	6
unit	function data	weight	weight	weight	weight
0x01	0b____0000	0x1_	0x2_	0x3_	0x4_

Hint: _ means irrelevant data

Unit

Each value is binded directly to the unit:

value	unit
1	g
2	oz
4	oz:lb
8	ml
16	fl.oz
20	kg

Function data

4 youngest bits from value are responsible for signalization of different functions.

bit number	function
0	measurement is finished
1	scale is overloaded
2	low battery
3	measurement is negative

Weight data

Four oldest bits from weight fields (3-6) concatenated together in hex notation are giving to total measurement. It depends of the unit if we need to recalculate result or not.

unit	formula
g	f(x) = x
oz	f(x) = round(35.274 * x / 100) / 10
oz:lb	oz: f(x) = (3.5273962 * x / 100) / 16
	lb: f(x) = (3.5273962 * x / 100) - 16 * oz
ml	f(x) = x
fl.oz	f(x) = round(35.195 * e / 100) / 10
kg	f(x) = x / 1000

Example:

Unit: kilograms

3	4	5	6
0x0F	0x1F	0x2F	0x3F

• take four older bits from hex notation and concatenate them: 0x0123
• number in decimal form: 291
• get the formula from the table and calculate the result: 291 / 1000 = 0.291 kg