# Photon Test Breakout Board

**URL:** <https://community.particle.io/t/photon-test-breakout-board/33222>\
**Category:** Hardware\
**Created:** [May 28, 2017, 7:54am UTC](https://community.particle.io/t/photon-test-breakout-board/33222 "2017-05-28T07:54:28Z")\
**Posts on this page:** 1\
**Showing post:** 16

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**Author:** ![rocksetta](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/rocksetta/32/5099_2.png) [@rocksetta](https://community.particle.io/u/rocksetta)\
**Post date:** [June 7, 2017, 5:32pm UTC](https://community.particle.io/t/photon-test-breakout-board/33222/16 "2017-06-07T17:32:35Z")

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@bko in this post:

[[solved] Particle Photon not receiving i2c transmission](https://community.particle.io/t/solved-particle-photon-not-receiving-i2c-transmission/30704/7)

You have a very simple I2C Photon to Photon setup. I know the connections are:

```
// Photon I2C setup
// GND master to GND slave
// D0 (SDA = data) on master to D0 on slave
// D1 (SCL = clock) on Master to D1 on slave

```

but I am not sure about pullups when both Master and Slave are Photons both pullup to 5V or can both be pulled up to 3V3?. Any suggestions?

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