# I2C pull-up resistors on modules and breakout boards

**URL:** <https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472>\
**Category:** Hardware\
**Tags:** boron, argon\
**Created:** [June 4, 2020, 7:06am UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472 "2020-06-04T07:06:45Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![jonamleonel](https://avatars.discourse-cdn.com/v4/letter/j/3da27b/32.png) [@jonamleonel](https://community.particle.io/u/jonamleonel)\
**Post date:** [June 4, 2020, 7:06am UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/1 "2020-06-04T07:06:45Z")

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I will use 5 different sensor for an air quality monitoring system.  
If all the 5 module sensors have l2C pull-up resistors, the 5 resistors will be in parallel.

Could I lost communication? What should I do?

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**Author:** ![ScruffR](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/scruffr/32/6952_2.png) [@ScruffR](https://community.particle.io/u/ScruffR)\
**Post date:** [June 4, 2020, 7:17am UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/2 "2020-06-04T07:17:16Z")

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Ideally you’d only have one set of pull-ups on one bus. If all your modules have their own set, try deactivating/removing them from a few boards.  
2k2 should be the lower limit of all pull-ups on one line. You may get away with lower values but this will put more strain on the devices to actually pull low and the logic level might not got low completely.

Some testing with all pull-ups in place shouldn’t hurt the devices tho.

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**Author:** ![IOTrav](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/iotrav/32/7707_2.png) [@IOTrav](https://community.particle.io/u/IOTrav)\
**Post date:** [June 4, 2020, 2:50pm UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/3 "2020-06-04T14:50:58Z")

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Most generally the I2C pull up jumpers are not necessary. The Photon will internally pull the SDA and SCL lines high. The only time pull up jumpers are necessary is if you have a very long cable run to the sensors. I would try without any of the jumpers installed to start.

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**Author:** ![ScruffR](https://sea2.discourse-cdn.com/flex026/user_avatar/community.particle.io/scruffr/32/6952_2.png) [@ScruffR](https://community.particle.io/u/ScruffR)\
**Post date:** [June 4, 2020, 3:04pm UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/4 "2020-06-04T15:04:19Z")

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> [@IOTrav](#):
>
> The Photon will internally pull the SDA and SCL lines high

Hmm, I don't think this is the case tho'

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**Author:** ![jstobaugh](https://avatars.discourse-cdn.com/v4/letter/j/e480ec/32.png) [@jstobaugh](https://community.particle.io/u/jstobaugh)\
**Post date:** [June 5, 2020, 2:52am UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/5 "2020-06-05T02:52:48Z")

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I have had devices not respond if I forgot to put the resisters on .

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**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/particle/original/3X/6/4/64635adccc35238caa19e9b553ec3e98b163d026.png) [@system](https://community.particle.io/u/system)\
**Post date:** [December 4, 2020, 2:52pm UTC](https://community.particle.io/t/i2c-pull-up-resistors-on-modules-and-breakout-boards/56472/6 "2020-12-04T14:52:49Z")

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