usb-meter

Python library for USB-C power meters. Initial support: ChargerLAB POWER-Z KM003C over its HID transport.

The library talks directly to /dev/hidraw*, so it does not fight with the upstream Linux powerz kernel driver (which binds to the device's vendor-bulk interface and exposes a small subset of values via hwmon). It also has no third-party dependencies.

Features

• Find a connected meter by USB vendor/product id.
• Read ADC samples (VBUS, IBUS, VCC1/2, VDP/M, VDD, temperature).
• Compact wire-protocol primitives (message + extension header, opcode and attribute enums) shared with the KM002C.
• usb-meter CLI for one-shot and streaming reads.

Installation

Directly from GitHub:

pip install git+https://github.com/nbuchwitz/usb-meter.git

Or from a local checkout:

pip install .

Install the udev rule so non-root users in the plugdev group can access the device:

sudo install -m 644 etc/udev/rules.d/60-chargerlab-km003c.rules /etc/udev/rules.d/
sudo udevadm control --reload && sudo udevadm trigger

Usage

from usb_meter import KM003C

with KM003C.open() as meter:
    sample = meter.read_adc()
    print(f"{sample.vbus_v:.3f} V, {sample.ibus_a:.3f} A, {sample.temperature_c:.1f} C")

Or from the shell:

usb-meter -n 10 -i 0.2     # 10 samples, 200 ms apart
usb-meter -n 0             # stream forever

Status

Alpha. Only ADC reading is implemented today. The vendor protocol documents more attributes (PD_PACKET, ADC_QUEUE_10K, SETTINGS, etc.) that map to the same request/response shape and will land here incrementally.