Hi all, I’m currently pursuing a project where I want to connect three VEML 7700 light sensors to a Raspberry Pi over a long distance (approx. 5 meters). For this purpose, I plan on using two PCA 9615 endpoints, but I’m unsure if I can handle the power supply through the CAT cable (though as far as I understood, it should work without any jumpers cut). I’m also worried about voltage drop across the cable length.
I created a crude wiring diagram for how I’m planning to do this. If someone would be so nice and check if it would work as planned, that would be greatly appreciated!
That should be fine (If I remember right we test much longer distances without issue), though I’d note you’ll need to disable any pull-up resistors on the VEML’s and that mux if they have them
Thanks for the reply. The mux and VEML’s do have pullups on the I2C lines but no jumpers to disable them unfortunately. Might I get away with enabling the internal pullups of the Raspberry Pi?
I’ve used these line-drivers (end-points) in many of my designs without much issue. I’m not sure what my max distance has been, but I think your 5 meters will be fine. Remember, you can always adjust the differential resistors to ‘tune’ your distance.
On a sidenote, I also run 12V and its GND through the extra pair over the RJ45/CAT5. However, hotswapping can easily damage devices. Not sure if hotswapping with a normal setup causes damage or not either, but I would power down just to be safe.
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Maybe, you’d have to test it in-hand…you might also have to sever the pull-ups if there isn’t an easier way to disable them