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# TMP36 Temperature Sensor with an ESP32 DevKit V1

On the ESP32 DevKit V1 the TMP36 takes its power from 3V3, well inside its 2.7 V to 5.5 V supply range, and its VOUT goes to GPIO33, an ADC1 input that keeps sampling while Wi-Fi is on. The sketch reads that pin with analogReadMilliVolts() instead of scaling raw counts, because the ESP32's 12-bit ADC is not linear and the calibration ESP-IDF finds in the chip's eFuses corrects it.

## Wiring

| TMP36 Temperature Sensor | ESP32 DevKit V1 | Note |
| --- | --- | --- |
| VCC | 3V3 |  |
| VOUT | GPIO33 (D33) |  |
| GND | GND |  |

## What to know on the ESP32 DevKit V1

- GPIO33 is ADC1_CH5. The ADC2 pins are shared with the Wi-Fi driver and stop giving readings once it starts, so a thermometer that reports over the network belongs on GPIO32 to GPIO39. (Espressif ESP32 Series Datasheet v5.3, pp. 14, 46; ESP-IDF Programming Guide, ADC Oneshot Mode Driver)
- The sketch puts GPIO33 at 11 dB attenuation, which arduino-esp32 rates from 150 mV to 2450 mV on the ESP32. The TMP36 gives 100 mV at -40 °C and 1.75 V at 125 °C, so only readings colder than about -35 °C fall under that floor. (arduino-esp32 2.0.17 ADC API documentation, analogSetAttenuation(); ADI TMP35/36/37 datasheet Rev. F, pp. 3, 8)
- analogReadMilliVolts() follows the attenuation set on the pin, so ADC_6db (150 mV to 1750 mV) is a valid swap if you want finer steps: it still covers -35 °C to 125 °C, and the (V - 0.5) x 100 conversion stays the same. (arduino-esp32 2.0.17, cores/esp32/esp32-hal-adc.c, __analogReadMilliVolts(); ADI TMP35/36/37 datasheet Rev. F, p. 8)
- Espressif gives the ADC a differential nonlinearity of up to ±7 LSB and recommends filtering or averaging several samples, which is why the loop adds eight millivolt readings before converting. (Espressif ESP32 Series Datasheet v5.3, p. 43)
- The sensor's output can supply only 50 µA, so GPIO33 should be the only thing on VOUT; ADI's decoupling is a 0.1 µF ceramic from +VS to GND right at the sensor. (ADI TMP35/36/37 datasheet Rev. F, pp. 3, 10)

## Code

```cpp
// TMP36 Temperature Sensor on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/tmp36/esp32
const int VOUT_PIN = 33;          // TMP36 VOUT on GPIO33 (ADC1)

void setup() {
  Serial.begin(9600);
  analogSetPinAttenuation(VOUT_PIN, ADC_11db);   // 11 dB, the widest range: Espressif rates it accurate to about 2.45 V
}

void loop() {
  // analogReadMilliVolts() applies the chip's own ADC calibration: the ESP32's
  // 12-bit analogRead() is not linear, so raw counts * 3.3 / 4095 reads off
  uint32_t mv = 0;
  for (int i = 0; i < 8; i++) mv += analogReadMilliVolts(VOUT_PIN);
  float volts = mv / 8.0 / 1000.0;
  float tempC = (volts - 0.5) * 100.0;      // 0.5 V at 0 °C, 10 mV per °C
  float tempF = tempC * 9.0 / 5.0 + 32.0;
  Serial.print("Temperature: ");
  Serial.print(tempC, 1);
  Serial.print(" C  ");
  Serial.print(tempF, 1);
  Serial.println(" F");
  delay(1000);
}
```

Compiled for esp32:esp32:esp32 on 2026-10-30.

## Questions

### Why is my TMP36 reading wrong on the ESP32 with analogRead()?

Raw counts times 3.3 / 4095 assume a linear ADC with a 3.3 V full scale, and the ESP32 has neither at 11 dB. Use analogReadMilliVolts() as the sketch does, then subtract 500 mV and divide by 10 mV per degree.

### Which ESP32 pins can read a TMP36?

Any ADC1 pin, GPIO32 to GPIO39 (ESP32 datasheet, p. 46). GPIO33 is used here; avoid ADC2 pins if the project uses Wi-Fi (ESP-IDF ADC documentation).

### Can the TMP36 be powered from 5 V on an ESP32 board?

It tolerates 5 V and its output does not depend on the supply (ADI datasheet, pp. 3, 8), so VOUT stays under 2 V either way. 3V3 is simply the shorter wire and keeps every signal at the ESP32's own level.

## More

- [TMP36 Temperature Sensor reference](https://www.tinkered.ai/components/tmp36.md): pinout, specs, rules and common mistakes

## Try it

Tinkered simulates the TMP36 Temperature Sensor on the ESP32 DevKit V1 in the browser, with this wiring and code, free: https://www.tinkered.ai/components/tmp36/esp32