EMK850+ Low-Power Analyzer · Serial Driver + MCP Server

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Reverse-engineered the Yingjia EMK850+ serial protocol, providing a Python CLI and an MCP server (Streamable HTTP + REST) for automated µA/µW-level power acquisition and programmable power-supply control, closing the AI-driven low-power optimization loop.

Highlights

The stock EMK850+ analyzer has severe automation limitations: it only ships a Windows GUI with no open API, so it cannot connect to scripts, programs, or AI automation platforms, blocking automated power testing and device control and greatly limiting its use in batch testing, intelligent debugging, and low-power optimization iteration.

To address these pain points, this project reverse-engineers the protocol and upgrades the functionality, making it a perfect fit for automation scenarios:

• Full protocol reverse: completely reproduces the device's 64-byte fixed-frame, 0x33 header, 0x40 fragmentation serial protocol, precisely matching the device's native communication logic.

• More robust than the vendor app: a byte-by-byte streaming frame-sync state machine solves the byte misalignment, freezes, and data corruption caused by the vendor's block reads, greatly improving runtime robustness.

• Lightweight and ready to use: provides both a Python CLI and a FastAPI HTTP service, supporting script calls, CI integration, and AI automation, quickly enabling power reading and device output control.

• Solves a core debugging pain: supports programmable power-supply power-cycle, waking an MCU that has entered deep sleep and lost the debugger connection, resolving a core low-power debugging pain point.

• High-precision standardized acquisition: supports µA/µW-level precision power acquisition, with a no-load baseline-zero function to remove the device's no-load offset error, outputting clean, accurate voltage/current/power measurements; every feature is HTTP-exposed for seamless integration into any automation or AI pipeline.

Related MCP server: UART MCP Server

Quick start

Read power from the CLI

uv sync
python emk850_analyzer.py power COM19

Voltage: 4.202 V   Current: 6.940 uA   Power: 29.20 uW

Run the server (REST + MCP)

python emk850_mcp_server.py --port COM19 --http 37749

The app is now a real MCP server (Streamable HTTP transport) while still exposing the REST endpoints, both in one process:

• REST: open http://localhost:37749 — any HTTP client works for power query, output control, zeroing, and device status.

• MCP: connect to http://localhost:37749/mcp — works with Claude Desktop, Cursor, MCP Inspector, and any other MCP client.

REST endpoints:

MCP tools (auto-derived from the REST routes, named by route operationId):

Connect an MCP client

MCP endpoint: http://localhost:37749/mcp

• MCP Inspector / debugging tool: pick the Streamable HTTP transport, point it at http://localhost:37749/mcp, and you can initialize, list the tools above via tools/list, and call them via tools/call.

• Claude Desktop / Cursor: register the URL as a remote MCP server.

Use case: wake a sleeping MCU

In low-power scenarios the MCU enters deep sleep and the debugger disconnects; use the instrument to power-cycle it awake:

1. Cut power: POST /output {"state":"off"}

2. Wait 10-15 s for caps to discharge

3. Restore 3.3V: POST /output {"state":"on","voltage":3.3}

4. Chip resets, debugger reconnects

Note: "off" sets 0mV because the protocol has no direct off command. At 0mV the sense terminals still read ~2.6V; verify with a multimeter before assuming the DUT actually lost power, don't rely on this alone to judge that the chip powered down.

Protocol highlights (reverse-engineered)

• Serial link: 115200 / 8N1

• Frame: fixed 64 bytes, header 0x33, with 0x40 continuation-frame fragmentation

• Gotcha: discard the vendor's block-read approach; use a streaming state machine to guarantee sync reliability.

Full command table and conversion math are in docs/EMK850_PROTOCOL.md.

Caveats

• The serial port is exclusively occupied; while the HTTP server runs, do not use the vendor app at the same time.

• No-load zeroing requires disconnecting all loads, otherwise measurement error is introduced.

• The device auto-ranges; current data on uncalibrated gears will be automatically skipped.

Disclaimer

This project's protocol was obtained by reverse-engineering the vendor's host software and is unrelated to and not officially endorsed by the manufacturer (Yingjia / 英加). Firmware or model upgrades may cause incompatibility; use at your own risk.

Project: https://github.com/createskyblue/Yingjia_EMK850_low-power_analyzer_MCP