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Docs Onboarding Common Beginner Mistakes

Common Beginner Mistakes

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The ten mistakes that cause the most forum posts, and how to avoid each one before it costs you a weekend.

Common Beginner Mistakes

These are the failure modes seen over and over again in first builds. Read this page before you solder anything.

1. Not wiring the BUSY pin

The SX1262 BUSY pin (GPIO 21) is mandatory. If it is not connected, the firmware hangs on the first radio call and the beacon appears dead. This is the single most common cause of “my beacon does nothing”.

2. Feeding 5 V to a 3.3 V part

The E22 radio, the OLED, and the GPS all run at 3.3 V (the GPS tolerates 3.3-5 V, but the radio does not). Use the ESP32’s 3V3 rail, never VBUS.

3. Reversing the battery polarity

The TP4056 BAT+ output and the 18650 holder can be wired backwards. Check polarity twice; a reversed cell can destroy the ESP32.

4. Using an I2C OLED

The firmware drives a 7-pin SPI SSD1309. A 4-pin I2C SSD1306 will not work without firmware changes. Buy the SPI panel.

5. Charge-only USB cable

Flashing fails mysteriously with a cable that carries power but no data. Test the cable on any other device first.

6. Wrong GPIO for GPS RX

GPS TX (the module’s output) connects to GPIO 22 (a valid input). The module’s RX pin stays unconnected — the firmware never sends to the GPS. Wiring the module RX to anything and leaving its TX floating produces no fix and confusing serial output.

7. Antenna not actually connected

The E22 has an SMA connector. If you use a bare wire instead, or the SMA nut is loose, range collapses to meters. Verify continuity between the antenna base and ground plane.

8. Missing pull-ups on input-only pins

GPIO 34 and 35 (UP and DN buttons) have no internal pull-ups. Without external 10 kΩ pull-ups the buttons read random values.

9. Forgetting the antenna rule for tests

Transmitting with no antenna at all can damage the PA over time. Use a dummy load or a real antenna even for quick tests.

10. Skipping the battery divider check

The 100 kΩ/100 kΩ divider halves the battery voltage. If you use different values, the ADC reads wrong percentages. Measure with a multimeter: full cell should read about 2.1 V at the GPIO 36 midpoint.