Multiple I2C pullups?

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usaotearoa
 
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Joined: Tue May 23, 2023 2:27 am

Multiple I2C pullups?

Post by usaotearoa »

Hi there,
I have recently purchased the following components from your store!
Thank you for intl shipping, as a hobbyist getting components was so much simpler in the US.

1x BNO085
3x VL53L1CX

I intend to connect all of them to the same I2C bus on a raspberry pi.
Further I do have a custom made PCB, which breaks out the GPIO of the Raspberry pi. On this custom PCB I included
4.7k pull-up resistors, as they are close to the SBCs pins. Further there is a small smd header to plug-in an OLED display, also I2C.

The idea behind the custom PCB was, I can simply add the pull-ups close to source and than I wouldn't need to include them with any of the other I2C bus devices.

However, just realized that the components I bought all include their own I2C resistors.

Question: Do I need to de-solder the "supplementary" pull-up resistors, or not bother and just connect them all up?

Thanks

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adafruit_support_bill
 
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Joined: Sat Feb 07, 2009 10:11 am

Re: Multiple I2C pullups?

Post by adafruit_support_bill »

The pullups on most of our i2c boards are 10K. In most cases, that relatively 'weak' pullup allows you to have several on the same bus without the combined pullup strength causing issues.

With 4 sets of 10K pullups plus the 4.7K, your effective pullup resistance is about 1.6K which is on the strong side. I'd give it a try, you may be OK. If the Pi has trouble driving that, you can remove the 4.7Ks.

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