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Levoit UART Extractor — Saleae Logic 2 HLA

A High-Level Analyzer (HLA) for Saleae Logic 2 that decodes the Levoit flat-TLV UART protocol used by Core 300S / 400S / 600S and Vital 100S / 200S air purifiers.

Protocol

Packets start with 0xA5, followed by a message type byte, command bytes, a length byte, and a payload:

A5  <type>  <cmd0> <cmd1> <cmd2>  <len>  [payload...]  <checksum>
Type byte Label
0x22 SEND (ESP→MCU)
0x12 ACKN (MCU→ESP, Core/Vital)
0x52 RESP (MCU→ESP, Core 600S)

Decoded frames are displayed as:

[ESP->MCU] SEND(0x22) |  CMD=01 40 B0  |  PAY=01

Installation

  1. Open Logic 2
  2. Go to Extensions (puzzle piece icon) → Load Existing Extension
  3. Select the levoit_uart folder (the one containing extension.json)

Settings

Setting Options Description
Channel ESP->MCU / MCU->ESP / - Labels each frame with the traffic direction
Include Raw Bytes No / Yes Appends the full raw hex bytes to each frame

Usage

  1. Locate the correct solder points on the PCB — see the individual device README for the exact pads

    Note: The debug pin header RX/TX pins are used to flash the ESP32. They are not the UART line between the ESP32 and the MCU. Tap into the dedicated ESP↔MCU communication pads (test points or vias near the ESP32), not the header.

  2. Capture UART traffic at 115200 baud, 8N1 — connect a logic analyzer to both the ESP TX and MCU TX lines with shared GND
  3. Add an Async Serial analyzer on the ESP TX channel (115200 baud, 8N1)
  4. Add a second Async Serial analyzer on the MCU TX channel
  5. Add a Levoit UART Extractor HLA on top of the first Async Serial, set Channel to ESP->MCU
  6. Add a second Levoit UART Extractor HLA on top of the second Async Serial, set Channel to MCU->ESP

Both HLAs run side by side so you can see the full request/response exchange in one view.

What to Capture

Capture separate, clearly labelled dumps for each action — one action per capture makes it much easier to identify which bytes correspond to which command:

Dump Action
bootup Power on → wait until Wi-Fi connected and app shows online
speed_1-4_app Switch through fan speeds 1 → 2 → 3 → 4 via the app
speed_1-4_device Switch through fan speeds 1 → 2 → 3 → 4 via the physical buttons
mode_app Switch through all modes (Manual / Auto / Sleep / Pet) via the app
mode_device Switch through all modes via the physical buttons
auto_mode Switch through all auto mode sub-options (Default / Quiet / Room Size / etc.)
display_on_off Toggle the display on and off
child_lock Enable and disable child lock
timer Set a timer via the app
filter_reset Reset filter stats
(model-specific) Any unique features: lights, white noise, CO₂ sensor, etc.

Label each file clearly (e.g. core300s_2.0.11_speed_app.txt).

Use Export Data in Logic 2 to export the analyzer results as a text/CSV file. A plain text file with the decoded HLA output is all that's needed — no .sal session files.

Example: See devices/levoit-sprout/uart/uart_dumps for a real Sprout dump covering boot, speed switching, light modes, and white noise — each section labelled with the action performed.