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Revise I2C sensor wiring and notes for boards

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Updated wiring instructions for I2C sensors on various boards, including Heltec v3, T114, RAK4631, Xiao NRF52, and Xiao S3. Added notes for BME280 and BME680 sensors regarding I2C addresses and wiring requirements.
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2025-12-27 13:38:41 +07:00
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@@ -7,38 +7,38 @@ This is the instruction to add sensors to repeaters:
## 1. Quick Wiring
| Board | Wiring for I2C sensors | Notes |
| ------------- | ------------- | ------------- |
| Heltec v3 / v4 / WSL3 | 3.3v => 3.3v <br> GND => GND <br> 17 => SDA <br> 18 => SCL <br> GND => SDO | On Heltec v3, the GPIO17 and 18 are tiny pads in the middle of the board bottom. |
| Heltec T114 | 3.3v => 3.3v <br> GND => GND <br> **41** => SDA <br> **42** => SCL <br> 3.3v => SDO | [Not tested yet] PowerSaving should work with GPIO 41,42 |
| RAK4631 | 3.3v => 3.3v <br> GND => GND <br> SDA => SDA <br> SCL => SCL <br> 3.3v => SDO | Both firmwares work <br> PowerSaving has additional features |
| Xiao NRF52 | 3.3v => 3.3v <br> GND => GND <br> D7 => SDA <br> D6 => SCL <br> 3.3v => SDO | Both firmwares work <br> PowerSaving has additional features |
| Xiao S3 | 3.3v => 3.3v <br> GND => GND <br> D4 => SDA <br> D5 => SCL <br> 3.3v => SDO | Both firmwares work <br> PowerSaving has additional features |
| Heltec v3 / v4 / WSL3 | 3.3v => 3.3v <br> GND => GND <br> 17 => SDA <br> 18 => SCL <br><br> GND => SDO (BME280/680) | On Heltec v3, the GPIO17 and 18 are tiny pads in the middle of the board bottom. |
| Heltec T114 | 3.3v => 3.3v <br> GND => GND <br> **0.16** => SDA <br> **0.13** => SCL <br><br> GND => SDO (BME280/680)| Not tested yet |
| RAK4631 | 3.3v => 3.3v <br> GND => GND <br> SDA => SDA <br> SCL => SCL <br><br> GND => SDO (BME280/680) | Both firmwares work <br> PowerSaving has additional features |
| Xiao NRF52 | 3.3v => 3.3v <br> GND => GND <br> D7 => SDA <br> D6 => SCL <br><br> GND => SDO (BME280/680) | Both firmwares work <br> PowerSaving has additional features |
| Xiao S3 | 3.3v => 3.3v <br> GND => GND <br> D4 => SDA <br> D5 => SCL <br><br> GND => SDO (BME280/680) | Both firmwares work <br> PowerSaving has additional features |
## 2. Boards
This section is for boards with some notes.
## 2. Notes for Boards
### Heltec v3
On Heltec v3, the GPIO17 and 18 are tiny pads in the middle of the board bottom.
- It is small. So solder with care.
<img height="384" alt="image" src="https://github.com/user-attachments/assets/deb1808f-db8e-4134-bf51-b42ed2a308bc" />
## 3. Notes for I2C Sensors
## 3. I2C Sensors
This section will be updated to include all supported sensors.
### BME280
The BME280 is a compact environmental sensor by Bosch that measures temperature, humidity, and barometric pressure.
* Heltec v3 and v4 does not officially expose GPIO17 and 18. Therefore, we decided to use GPIO 41 and 42 for I2C sensor.
* The default I2C address for Adafruit BME280 is 0x77. You do not need to wire 3.3v to SDO
* For other BME280 boards, you are strongly recommended to wire 3.3v to SDO to force to use address 0x77. Else, the I2C address may jump either 0x76 and 0x77.
* MeshCore requires I2C address **0x76** for BME280
* For Adafruit BME280, you need to solder the Addr pad to use I2C address 0x76
* For other BME280 boards, you are strongly recommended to wire **GND to SDO** to force to use address 0x77. Else, the I2C address may jump either 0x76 and 0x77.
<img height="384" alt="image" src="https://github.com/user-attachments/assets/aef17a8b-994c-4090-84de-97d00e6d106c" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/488d290b-212e-4331-ac1a-e92bc1a964e5" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/c2f4bbce-9958-4203-a9aa-0a34634bf1f7" />
<img height="384" alt="image" src="https://github.com/user-attachments/assets/aef17a8b-994c-4090-84de-97d00e6d106c" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/488d290b-212e-4331-ac1a-e92bc1a964e5" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/d25c808f-5e58-4a0f-89ea-56e70fef6efb" />
### BME680
The BME680 is a compact environmental sensor by Bosch that measures temperature, humidity, barometric pressure, and air quality (gas/VOC).
* Note: As of 20 Dec 2025, MeshCore app can not show the Gas telemetry properly.
* Heltec v3 and v4 does not officially expose GPIO17 and 18. Therefore, we decided to use GPIO 41 and 42 for I2C sensor.
* The default I2C address for Adafruit BME280 is 0x77. You do not need to wire 3.3v to SDO
* For other BME680 boards, you are strongly recommended to wire 3.3v to SDO to force to use address 0x77. Else, the I2C address may jump either 0x76 and 0x77.
* Note: As of 20 Dec 2025, MeshCore app can not show the Gas telemetry properly in Channel 1 or 2.
* MeshCore requires I2C address **0x76** for BME680
* For Adafruit BME280, you need to solder the Addr pad to use I2C address 0x76.
* For other BME280 boards, you are strongly recommended to wire **GND to SDO** to force to use address 0x77. Else, the I2C address may jump either 0x76 and 0x77.
<img height="384" alt="image" src="https://github.com/user-attachments/assets/3dbdafc2-af58-4304-b5b6-221cc1817ce3" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/84393dbe-8ac5-4824-9a39-0a390db8c115" /> <img height="192" alt="image" src="https://github.com/user-attachments/assets/01494234-047b-49ee-96a0-3877ed307bd9" />