Programmers guide to the Half Decent Scale
Over bluetooth, these commands should be sent as binary
Over USB and Wifi, these commands should be sent as Hex strings
Also see the older Decent Scale API Docs. The Half Decent Scale is compatible with that command set, but adds a substantial number of new commands
A python library is also available
Javascript apps and weighing library (supporting Bluetooth, USB and Wifi!)
New 'heartbeat' feature solves connectivity issues with Android 9 and older.
- Apps need to send a 'heartbeat' at least every 5 seconds, or the bluetooth connection will be dropped
- The heartbeat command to send to the scale is: “03 0a 03 ff ff 00 0a”
- Why does this feature exist?
- Older Android versions have a problem where bluetooth connections are kept to devices, even though the app no longer has the connection.
- The heartbeat resolves that problem, and is the same approach Decent took with bluetooth on the DE1, to resolve the same issue.
- Older apps that are unaware of the heartbeat feature, will automatically disable the heartbeat requirement
- when they send the LED ON bluetooth command, with the 6th byte in that command set to 00
- or the TARE command with that last byte as 00.
- Apps that want to use the heartbeat feature (and it's highly recommended),
- should send 01 as the last data byte of the LED ON command, for example: “03 0A 01 01 00 01 08”
- should also send 01 as the last data byte of the TARE command, for example: “03 0F 01 00 00 01 0C”
- These variants of the LED ON and TARE commands will not have any negative effect on older Decent Scales, which don't have the heartbeat feature.
- DE1 users should upgrade to the NIGHTLY de1app dated April 11 or newer
Commands that HDS can receive(v2.5.8)
03 0F TARE (with checksum) (please read the note above regarding the heartbeat feature)
03 0A 00 Turn off oled
03 0A 01 Turn on oled (please read the note above regarding the heartbeat feature)
03 0A 02 Power off
03 0A 03 00 Exit power mode, normal oled brightness
03 0A 03 01 Enter power mode, lowest oled brightness
03 0B 00 Timer stop
03 0B 02 Timer reset
03 0B 03 Timer start
03 1A 00 Manual Calibration
03 1A 01 Smart Calibration
03 1B WiFi OTA
03 1D 00 Set sample to 1
03 1D 01 Set sample to 2
03 1D 02 Set sample to 4
03 1E 00 00 Hide Menu
03 1E 00 01 Show Menu
03 1E 01 00 Hide About info
03 1E 01 01 Show About info
03 1E 02 00 Hide debug info
03 1E 02 01 Show debug info
03 1F Reset
03 20 00 Disable Weight via USB
03 20 01 Enable Weight via USB
03 22 Send Battery voltage data once
Weight:
data = modelByte;
data = 0xCE; // Type byte for weight stable
data = weightByte1;
data = weightByte2;
data = 0x00;
data = 0x00;
data = calculateXOR(data, 6); // Last byte is XOR validation
Button event:
data = modelByte;
data = 0xAA; // Type byte for weight stable
data = buttonNumber;//1 for O button, 2 for ▢ button
data = buttonShortPress;//1 for short press, 2 for long press
// Fill the rest with dummy data or real data as needed
data = 0x00;
data = 0x00;
data = calculateXOR(data, 6); // Last byte is XOR validation
Power off event:
data = modelByte;
data = 0x2A;
data = buttonNumber;
data = buttonShortPress;
data = 0x00;
data = 0x00;
data = calculateXOR(data, 6); // Last byte is XOR validation
Battery Voltage:
data = modelByte;
data = 0x22;
data = voltageByte1;
data = voltageByte2;
data = 0x00;
data = 0x00;
data = calculateXOR(data, 6); // Last byte is XOR validation
Debugging via USB
You can connect a USBC cable and used a program such as Serial with settings of 115200,8,N,1 to watch the scale in operation. This makes debugging extremely easy.
#programmer #api #bluetooth #wifi #usb
Updated 2025/02/26