1

enter image description hereI try to connect a Sensirion SPS30 Particle Sensor to my Raspberry Pi 3B via I2C. There are other sensors on the I2C Bus - and they work without any problems, but I fail to detect the SPS30.

What I have tried:

  • The SPS30 is connected to 5V, Pins 4 & 5 are connected to GND
  • I use a splitter (3K/2K) to connect SDA/SCL, and the I2C lines are all pulled-up to 3V (it doesn't work without any pull-up/pull down resistors, I think I tried many possible combinations)
  • I've set the baudrate to 100,000 (dtparam=i2c_arm=on,i2c_arm_baudrate=100000)

None of this seems to work.

Does anyone have any suggestions what else to try?

uname -a
Linux raspberrypi 5.10.17-v7+ #1403 SMP Mon Feb 22 11:29:51 GMT 2021 armv7l GNU/Linux
Improve this question
2
  • Clear photos showing the connections may help.
    – joan
    Commented Apr 19, 2021 at 12:23
  • I've added the circuit - thanks!
    – Gux
    Commented Apr 19, 2021 at 13:01

1 Answer 1

Reset to default
1

It is unclear what you are trying to do but this is certainly not the way to do it.

The Pi has pull-ups on I²C lines so none are needed.

The series resistors will effectively prevent anything from working; I²C uses open drain circuitry.

Most I²C devices will work at 3.3V if there are no pullups to 5V, occasional devices need higher voltages and require a level converter.

See rPi3 I2C-LCD, do i need a logic level converter?

Improve this answer
4
  • The resistors are to get from 5V to 3.3V on SDA/SCL - I've noticed that the pull-up resistors don't do anything. Bu even when I connect the SPS30 directly to SDA/SCL I can't detect it (e.g. with i2cdetect)
    – Gux
    Commented Apr 19, 2021 at 13:24
  • You obviously don't understand how the circuit works and the bus is bi-directional. You need NO pull-ups on the devices BUT if they have pull-ups you need a level converter.
    – Milliways
    Commented Apr 19, 2021 at 13:28
  • Thanks - this explains a lot! I'm sorry, this is my first excursion into this type of electronics, I used to stay away from hardware if possible.
    – Gux
    Commented Apr 19, 2021 at 13:35
  • I have added a Level Converter - but still without success unfortunately. It is connected to 5V on HV and 3.3 V on LV - and SDA and SCL are both passed through.
    – Gux
    Commented Apr 20, 2021 at 15:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.