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Troubleshooting

This page lists common issues and quick checks when using the TMP117 High-Accuracy Temperature Sensor.

  • Make sure wiring is correct:

    • 3V3 / VCC → 3.3 V (or 5 V if using onboard regulator)
    • GND → GND
    • SDA → SDA (e.g., IO21 on ESP32)
    • SCL → SCL (e.g., IO22 on ESP32)
    • ALERT → optional (any GPIO if used)

  • Default I²C address is 0x49.
    Depending on ADD0 connection, addresses can be:

    • 0x48 – ADD0 → GND
    • 0x49 – ADD0 → VCC (default)
    • 0x4A – ADD0 → SDA
    • 0x4B – ADD0 → SCL

  • Run an I²C scanner sketch to confirm the device appears on the bus.

  • Verify pull-up resistors (~10 kΩ) are present on SDA, SCL, and ALERT (they are included on the breakout).

  • This usually means the sensor did not respond or the I²C transaction failed.
  • Ensure correct wiring and that the sensor has stable power (1.7–5.5 V).
  • If using multiple sensors, check that each has a unique address.
  • Confirm your code calls tmp.init() before attempting to read.
  • Allow the sensor to thermally stabilize after power-up (~1 s).
  • Avoid touching the sensor during measurement — body heat can cause drift.
  • Verify averaging mode: use tmp.setAveraging(TMP117_AVE::AVE8) for smoother results.
  • Ensure no strong heat sources (voltage regulators, Wi-Fi chips) are close to the sensor.
  • If readings are offset by a fixed amount, use tmp.setOffsetTemperature(x) for calibration.
  • Typical conversion time is 15.5 ms per measurement (one-shot mode).
  • Continuous mode defaults to 1 Hz sampling with optional averaging.
  • The ALERT pin is open-drain and needs an external or onboard pull-up resistor (~10 kΩ).
  • By default, ALERT is active low, but it can be inverted via the POL bit in the configuration register.
  • Make sure alert thresholds are configured: 
    tmp.setHighLimit(28.0);
    tmp.setLowLimit(20.0);
    tmp.enableAlertMode();
  • Confirm the correct alert mode (therm or data ready) is selected.
  • EEPROM access requires the sensor to be idle (not converting).
    Use tmp.setConvMode(TMP117_CMODE::SHUTDOWN) before reading EEPROM.
  • EEPROM writes require about 7 ms per write cycle. Avoid power-off or I²C activity during that period.
  • Confirm correct register address if reading manually over I²C.
  • Avoid powering off the board while writing to EEPROM — incomplete writes may corrupt data.
  • Ensure solid I²C connections — intermittent SDA/SCL can cause bus lockups.
  • Avoid long jumper wires (>30 cm) without proper pull-ups.
  • If using 5 V logic (e.g., Arduino Uno), make sure to use a level shifter if the sensor runs at 3.3 V.
  • Power the sensor from a stable 3.3 V regulator; brownouts can reset communication.
  • Check that the Serial Monitor baud rate is set to 115200.
  • Make sure Serial.begin(115200) is called before printing.
  • Upload the sketch again — sometimes the board needs a full reset after connecting peripherals.