GPS Modules for LoRa Nodes
GPS provides automatic position reporting for mesh mapping and navigation. Many boards include an integrated GPS; for those that don't, external GPS modules can be added via UART or I2C.
Integrated GPS vs External Module
| Approach | Boards | Pros | Cons |
|---|---|---|---|
| Integrated GPS | T-Beam, T-Echo, some RAK boards | All-in-one, no wiring | Higher cost; disabling GPS to save power depends on whether the board provides GPS power gating (some integrated boards switch GPS power via the PMIC/GPIO, others do not) |
| External UART GPS | Any board with UART pins | Flexible, replaceable, can be positioned for best sky view | Wiring required, adds bulk |
| GPS from phone via BLE | Any (Meshtastic only) | No hardware needed | Requires active phone connection; phone must remain near node |
Popular External GPS Modules
| Module | Interface | TTFF (cold) | Current Draw | Notes |
|---|---|---|---|---|
| u-blox NEO-M8N | UART | 26s | 23 mA | Excellent sensitivity; widely supported |
| Quectel L76K | UART | 30s | ~29 mA (acquisition/tracking) | Used on the LilyGO T-Echo (and some Wio Tracker L1 boards); compact. The T-Beam Supreme uses a u-blox M10-series module, not the L76K |
| u-blox MAX-M8Q | UART | 26s | 15 mA | Compact form factor; patch antenna |
| ATGM336H | UART | ~35s | ~20 mA | Inexpensive Chinese alternative; adequate for most uses (figures approximate) |
| GT-U7 (NEO-6M clone) | UART | 60s+ | ~45 mA | Very inexpensive; poor sensitivity; not recommended (figures approximate) |
TTFF = Time To First Fix from a cold start in open sky conditions.
Wiring an External UART GPS
Most GPS modules use 3.3V logic and UART at 9600 baud. Connect:
- GPS VCC → 3.3V on LoRa board
- GPS GND → GND on LoRa board
- GPS TX → UART RX pin on LoRa board
- GPS RX → UART TX pin on LoRa board (needed only if sending commands to GPS)
Configure in Meshtastic: Config → Position → GPS Mode = Enabled; GPS RX pin = RX pin number from your board's pinout.
GPS Power Management
GPS is one of the largest power consumers on a LoRa node. For battery-powered nodes:
- Disable GPS if fixed position is configured - A repeater at a known location doesn't need active GPS
- Increase GPS update interval - For slow-moving applications, a 60-300 second GPS update interval with smart beaconing works well
- GPS power gating - Some boards route GPS power through a GPIO-controlled switch. Meshtastic can be configured to power-cycle the GPS between fixes, which can substantially reduce average GPS current; the exact average depends on the module and update interval
- Almanac caching - After a successful fix, Meshtastic caches almanac data to flash and reloads it on boot, enabling faster warm starts on subsequent power-ups. Meshtastic has no internet/app-based AGPS preload feature; it does not download almanac or ephemeris over WiFi/internet