Hardware bring-up

This build targets the official K151 StackChan. A similarly named DIY robot can have different servos, PSRAM, power hardware, and GPIO assignments. Do not assume compatibility.

See the GPS presets, baud finder, compatibility table, and DIY ATGM336H wiring guide. Custom RX supports only the six exposed Grove signal pins.

The GPS Unit and stackable GPS Module/Module GPS v2 are different products. Verify the actual model, cable orientation, UART voltage, baud, and switch/pin routing. The default profile is for an external UART unit connected through Port C. Never connect RS-232 voltage levels directly to ESP32 GPIO. GPS settings cannot be changed during an active recording session.

Before installing:

1. Identify the USB port by unplugging/reconnecting just StackChan. Close M5Burner and serial monitors using it.
2. Enter download mode using the bottom RST button held for around three seconds, then released at the green LED, according to the K151 documentation. The side power button held for six seconds turns it off instead.
3. Read the chip identity and flash size with esptool. Save a full 16 MB flash backup outside Git (the ignored backups/ directory is suitable). Factory backups may contain Wi-Fi credentials and pairing data; do not publish them.
4. Build, then flash only the verified port. The partition layout reserves 5 MB per app slot. This is not an OTA-compatible update to the factory application.
5. Confirm the display, touches, SD mount, speaker, and GPS NMEA byte counter. Wait outdoors for a fix. Validate a saved CSV before relying on a drive.
6. Check mechanical clearance and enable Motion. Avoid pulling on the head. If calibration is wrong, switch Motion off and restore/calibrate with the official firmware before retesting.

Example with an installed esptool (replace the port):

esptool --chip esp32s3 --port YOUR_PORT flash-id
esptool --chip esp32s3 --port YOUR_PORT read-flash 0 ALL backups/factory.bin

Esptool 4 uses underscore command names (flash_id, read_flash). Restoring a complete verified backup overwrites the current firmware and settings. M5Burner also offers the factory firmware; follow M5Stack's restoration instructions.

Use the packaged split-image instructions with DIO bootloader flash mode. The QIO/QSPI Arduino memory profile enables runtime Quad flash/PSRAM access; forcing a QIO bootloader header caused a watchdog reset loop on the tested K151. Preserve the NVS sectors and factory servo calibration. LCD rotation 1 provides the 320 × 240 landscape interface.

The project carries a scoped Espressif SD-driver backport for card initialization and completed writes. Shared Arduino/PlatformIO package files are not modified. SD mount starts at 4 MHz and retries at 1 MHz if needed.

USB maintenance commands are supported by tools/device.py --port YOUR_PORT COMMAND: STATUS, SCREEN, TAP x y, START, STOP, GPS FIND, GPS CANCEL, and CHECK LOG. STATUS includes NMEA checksum counters, mounted SD capacity, food progress, and storage errors. After stopping, CHECK LOG reopens the latest session and checks its WiGLE header and file size.

SOUND TEST plays a short diagnostic tone and reports the playback configuration and amplifier registers; SOUND STATUS reads those diagnostics without playing anything. The explicit tone test can sound even if normal companion sounds are set to Quiet.

The destructive command FORMAT SD <exact_bytes> performs a FAT32 quick format of the inserted card, removing all its files. It refuses while recording or if the supplied capacity does not match. For a card without a mountable FAT filesystem, it initializes the physical card and reads its capacity again before writing anything. Use only when intentionally erasing that card; this is not secure data erasure. Large cards can take several minutes; keep power connected until FORMAT OK or a failure response arrives. Normal boot and SD retry never format a card.

Official references: StackChan pin map/download mode, SD example, servo BSP.