serial-scale-bench

Python driver for RS-232/USB commercial bench scales (Kern, Mettler-Toledo, etc.).

Supports two ASCII response protocols:

• Protocol 1 — multi-line header responses (GS, NT, GT prefixes); typical of Kern and similar label-printing scales
• Protocol 2 — single float line; minimal scales and simpler firmware

Protocol is auto-detected on first connection. A FastAPI HTTP server is included for running the scale as a networked service (e.g. LabWatch integration).

Install

Base (serial only):

pip install serial-scale-bench

With HTTP API server:

pip install "serial-scale-bench[api]"

Or editable from this repo:

pip install -e .

Usage

from serial_scale_bench import SerialScale

scale = SerialScale(port="/dev/ttyUSB0", baudrate=9600)
scale.tare()
weight = scale.get_weight()   # float grams or None
scale.close()

Auto-reconnect wrapper

from serial_scale_bench import AutoReconnectSerialScale

scale = AutoReconnectSerialScale(port="/dev/ttyUSB0")
weight = scale.get_weight()   # reconnects automatically on error

HTTP API server

Start a local REST server exposing the scale over HTTP:

python -m serial_scale_bench.entrypoint --device /dev/ttyUSB0 --port 8080 --scale-id bench1

Endpoints: GET /weight, POST /tare, POST /zero, GET /status, GET /ping.

API reference

Method	Description
get_weight()	Poll current weight (float or None)
tare()	Send tare command
zero()	Send zero command
set_tare_value(value)	Set absolute tare
is_connected()	True if serial port is open
is_responsive()	True if scale responds to ping
close()	Close serial connection

murineshiftwork integration

Planned: BenchScaleAdapter in murineshiftwork.logic.scale. Install with:

pip install "murineshiftwork[calibration]"