ESP32 + SX1276 gateway that receives RTCM3 corrections over a 433 MHz LoRa link, reassembles them, and re-serves them to nearby GNSS rovers through a local NTRIP caster on its own WiFi access point. Built around a commodity LoRa development board (no custom PCB), so this BOM lists ready-made modules and the few external parts that complete the build.
| Qty | Part | Description | Notes | Est. USD |
|---|---|---|---|---|
| 1 | LoRa dev board: TTGO LoRa32 V2.1 | ESP32 + SX1276 (433 MHz) + SSD1306 OLED | Firmware env ttgo-lora32-v21 |
18–28 |
| 1 | 433 MHz LoRa antenna | SMA dipole; yagi/directional for range | Must be 433 MHz, not 868/915 | 3–10 |
| 1 | Passive buzzer | Audible pulse on every valid RTCM frame | Driven from GPIO4 | <1 |
| 1 | 18650 Li-ion cell (3.7 V) or USB-C supply | Field power | LoRa32 V2.1 has an 18650 holder | 5–9 |
| 1 | USB-C cable | Programming / power | — | 2–4 |
| Qty | Part | Description | Est. USD |
|---|---|---|---|
| 1 | SSD1306 128x64 OLED | Only if board variant lacks the onboard display | 3–5 |
| 1 | Enclosure (weatherproof if outdoor) | Field deployment | 5–20 |
| 1 | SMA pigtail / extension | Mount antenna externally | 2–5 |
Indicative total: ~$30–50 (LoRa32 V2.1 + 433 MHz antenna + buzzer + battery).
NSS → GPIO18 MOSI → GPIO27 MISO → GPIO19
SCK → GPIO5 RST → GPIO14 DIO0 → GPIO26
I2C: SDA → GPIO21, SCL → GPIO22, RST → GPIO16
Signal → GPIO4 (non-blocking pulse on valid RTCM frame)
| Parameter | Value |
|---|---|
| Frequency | 433.7 MHz (433700000) |
| Spreading factor | 7 |
| Bandwidth | 500 kHz |
| Coding rate | 4/5 |
| TX power | 20 dBm |
| Sync word | 0x12 |
⚠️ These radio parameters must be identical to the transmitter or the link fails silently.