I2C Channel Noise

[hsynklc]

Hello, I'm trying to use 12 vl53l1x(ToF) sensors with the stmf407vgt6 custom card. In addition, this board has a 5A 2 channel motor driver. I think the i2c data is getting noise during the motor start cycle. I tried to reduce the noise with filters (FIR, IIR etc.) but I haven't been able to do it yet. How can i fix this problem?

[LCE]

What's your setup, already routed PCB?
If not, use some shielded cables, keep them away from the motor supply, and improve the filter.

Keep in mind that GND is not some magic zero impedance 0V sink, but a real life return path for currents.

[hsynklc]

Should I use shielded cables for all cables? Is it enough if I use shielded sda-scl cable near the motor source? And how can i improve filter for i2c channel? Can you suggest a specific filter to reduce i2c data noise.

[LCE]

Shielded cable: trial and error... make sure the cable shield is only connected on one side, don't use it as ground connection.
So, best cable would be with 3 cores (SCL, SDA, GND) and shield (connect on one side only to "noise free GND point" - if such exists...).

Filter: I meant the motor supply... big common mode choke, big capacitors

If you want to filter I2C, try some ferrite beads (or some 22R resistors) + a few pF caps, maybe reduce I2C speed.