# External I2C bus / NFC

## Connector pinout

| Pin | Signal  | Voltage |
| --- | ------- | ------- |
| 1   | VCC     | +5.0V   |
| 2   | I2C SCL | +3.3V   |
| 3   | I2C SDA | +3.3V   |
| 4   | NFC IO  | +3.3V   |
| 5   | GND     | GND     |

## RDDRONE-FMUK66 Rev. C schematic

![](https://1329960936-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-L9GLtb-Tz_XaKbQu-Al%2F-LVsC1W9Lh4_z_Pu846c%2F-LVsCAdwwWIyZDa3gNJh%2FC-I2C.png?alt=media\&token=a2b68ee8-52d5-421c-9fe9-36de093dda68)

## RDDRONE-FMUK66 Rev. B schematic

{% hint style="danger" %}
Rev. B (and older boards) are **not supported** anymore. This information is left for reference.
{% endhint %}

![](https://1329960936-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-L9GLtb-Tz_XaKbQu-Al%2F-LOrvCVzlhjwif35PmiG%2F-LOrtwx4_Jk6GwbZeBpb%2Fnfc-i2c.PNG?alt=media\&token=201b9fdf-b145-447f-9485-14d180afe41f)