dps150

A command-line tool to read and control a FNIRSI DPS-150 programmable bench power supply over USB serial. Single file, pyserial only. It speaks the DPS-150's binary protocol directly.

The main intended use is driving the supply from agentic AI automation tools such as Claude Code. The one-shot commands and --json output let an agent set a rail voltage, read back the state, log current draw, or cut power while it works a board on the bench. It also works by hand or from a shell script. Read the safety notes below before letting anything change the output automatically.

Read live output voltage/current/power, input rail voltage, temperature, CC/CV mode, and protection state; set output voltage and current limit; turn the output on/off; set OVP/OCP/OPP/OTP/LVP trip points; read energy metering and firmware/model info.

Install

git clone https://github.com/cajunpanda/dps150
cd dps150
pip install pyserial

Run ./dps150.py by path (it's executable), or symlink it onto your PATH.

Install as a Claude Code skill

The repo contains a SKILL.md, so it works as a Claude Code skill. Point Claude Code's skills directory at the clone; a symlink means git pull updates it in place:

# personal skill (all projects)
ln -s "$PWD" ~/.claude/skills/dps150

# or a single project
ln -s "$PWD" /path/to/project/.claude/skills/dps150

Then ask Claude Code to read the supply, set a voltage, or turn the output off. pyserial must be installed in the Python Claude Code runs.

Device and port

The DPS-150 enumerates as an AT32 USB-CDC virtual COM port (VID:PID 2e3c:5740, description "AT32 Virtual Com Port"), normally /dev/ttyACM0 on Linux. The tool auto-detects it. Override with --port <path|by-id-substring> or the $DPS150_PORT env var. Run ./dps150.py ports to list candidates (the DPS-150 is marked <- DPS-150).

--port matches a full device path (/dev/ttyACM0) or a substring of the /dev/serial/by-id link name (AT32). A bare ttyACM0 is neither and will not match, so use the full /dev/ttyACM0.

Each run opens the port, does the connect handshake, does its work, and disconnects. The handshake only starts and stops the telemetry stream; it does not change the output state or stored setpoints.

Commands

Command	What it does
status (default)	Read and print full state. --info also queries model/hw/fw.
watch [--interval S]	Live V/I/P line, updates until Ctrl-C.
voltage <V> [--on]	Set output voltage. --on also enables output.
current <A> [--on]	Set current limit.
set <V> <A> [--on]	Set voltage and current limit together.
on / off	Enable / disable the output.
ovp <V> ocp <A> opp <W> otp <C> lvp <V>	Set a protection trip point.
display [--brightness 0-10] [--volume 0-10]	Screen brightness / beeper.
meter start|stop	Energy (Ah/Wh) accumulation.
info	Model, hardware, firmware version.
ports	List serial ports.

Global flags: --json (machine-readable state dict), --port, --timeout, --no-rtscts (disable hardware flow control; try this if reads ever hang).

Examples

./dps150.py status                 # human-readable snapshot
./dps150.py --json status          # dict for parsing / logging
./dps150.py voltage 5.0            # set 5.0 V (leaves output state as-is)
./dps150.py set 3.3 1.0 --on       # 3.3 V, 1.0 A limit, output on
./dps150.py current 0.25           # tighten current limit to 250 mA
./dps150.py off                    # kill the output
./dps150.py watch                  # stream V/I/P live
./dps150.py ovp 6.0                # OVP trips at 6.0 V

Reading state in JSON

--json emits a flat dict. Keys: out_v out_i out_p (measured), set_v set_i (setpoints), input_v temp_c mode (CC/CV), output_on (bool), protection (OK/OVP/OCP/OPP/OTP/LVP/REP), ovp ocp opp otp lvp, limit_v limit_i (device max), capacity_ah energy_wh metering_on, brightness volume, and with --info: model hw_version fw_version.

Safety notes

• The output may already be on and powering a live board. Check status before changing voltage or output state. off is always safe.
• Setting voltage or current does not by itself enable the output; use on or --on when you want power delivered.
• The device streams telemetry only while connected, so a status read merges a full snapshot with live measurements over about 0.8 s. Brief read latency is normal.

Tested hardware

Tested only with the FNIRSI DPS-150. It is specific to that model's serial protocol and will not work with other supplies.

Protocol

Serial 115200 8N1, hardware (RTS/CTS) flow control. TX packet [0xF1, cmd, type, len, data..., checksum], RX header 0xF0; checksum = (type + len + sum(data)) % 256; floats little-endian IEEE-754. The full type-code table and packet parser are documented inline in dps150.py.

The protocol was reverse-engineered by cho45 and KochC; this tool is an independent implementation based on their findings. Thanks to both.

License

MIT, 2026 Aaron Perkins. See LICENSE.