Build Guide — Sigma Iota GPS NAV

STEP

01

HARDWARE

BUY THE HARDWARE

The GPS NAV runs on the M5Stack Tab5. You will also need a compatible GPS module, a 128GB MicroSD card, and a USB-C cable for flashing.

M5Stack Tab5 — the main device
GPS/BDS Unit V1.1 (AT6668) — attaches via the Tab5 Grove port
128GB MicroSD card — for map data and documents
USB-C cable — data capable (not charge-only)

Tab5 units labelled ST7121 (April 2026 revision) can use the optional ST7121 test firmware in step 3. Display and touch support is awaiting testing on a physical ST7121 device.

BUY TAB5 → BUY GPS MODULE →

STEP

02

FIRMWARE

GET THE FIRMWARE

Purchase firmware access. One payment licenses a single physical device with free updates for life. No subscriptions.

Secure checkout via Stripe

ALREADY PURCHASED?

STEP

03

FLASH

FLASH THE FIRMWARE

REQUIRES FIRMWARE PURCHASE

Complete step 2 to unlock the web flasher.

Connect your Tab5 via USB-C, then click Connect & Flash. Your browser will ask you to select the serial port — choose the ESP32 device.

Requires Chrome or Edge (Web Serial API). The device's chip ID will be read before flashing and linked to your account.

Firmware version Regular firmware For ILI9881C and ST7123 displays. Includes the moon calendar. ST7121 test firmware — test 1 Adds April 2026 display and touch support. Awaiting hardware verification; includes the moon calendar.

Testing ST7121? Please check cold startup, touch at the corners and centre, brightness, and restarting. Report your results to contact@sigmaiota.uk, mentioning ST7121 test 1 and the controller printed on your Tab5 label.

Update firmware flashes app only — preserves your waypoints Full install erases everything — use for new devices or factory reset

✓ FLASH COMPLETE

Your GPS NAV is initialising. The device will restart automatically. Proceed to step 4 to write the map data to your MicroSD card.

STEP

04

SD CARD

PREPARE THE SD CARD

REQUIRES FIRMWARE PURCHASE

Complete step 2 to unlock the SD card writer.

BUILD YOUR GPS NAV

BUY THE HARDWARE

GET THE FIRMWARE

FLASH THE FIRMWARE

✓ FLASH COMPLETE

PREPARE THE SD CARD

✓ SD CARD READY