SHT40¶
Temperature and humidity over I2C, at address 0x44. Power first, then the two data wires.
Before you start
Checkpoint 2 passed. USB unplugged while you seat jumpers.
Warning
Power from 3V3 only. After wiring, check for heat and, if you have a meter, about 3.3 V on the supply pin.
The power pin may be printed VIN, VCC or VN. They all go to the 3V3 rail.
1. Power¶
| From | To | |
|---|---|---|
+ rail (3V3) |
SHT40 VIN / VCC / VN | |
− rail (GND) |
SHT40 GND |
Leave SDA and SCL open for now. Plug into COM and check that the module is cool. If you have a meter, expect about 3.3 V on the supply pin (optional):
Unplug before adding the data wires.
2. I2C¶
| ESP32 | SHT40 | |
|---|---|---|
| GPIO8 | SDA | |
| GPIO18 | SCL |
Both wires or neither. One alone will fail the later scan at 0x44.
Keep the buses apart
Do not join these to the display's SDA and SCL pins. Those are SPI.
If it fails¶
| Symptom | Fix |
|---|---|
| Module warm | Unplug. Check that VIN isn't on 5V and GND is on the − rail |
| Meter doesn't read about 3.3 V | Confirm the ESP32 still feeds the + rail (checkpoint 2) |
Flashing later shows no 0x44 |
Come back here. Check SDA and SCL aren't swapped, reseat both data jumpers, and shorten the wires |
Checkpoint 3¶
- SHT40 power is on 3V3 and GND only, taken from the breadboard rails (not daisy-chained off the display)
- GPIO8 to SDA and GPIO18 to SCL, both seated
- The module stays cool with COM plugged in (and about 3.3 V on the supply pin, if metered)
- No wires on the display yet
Stop here until every box is ticked.
Next: Display