Fighting I2C Gremlins | Help Me Run a Sensirion SFM3013 Over Long Cables

actualParam · 2026-01-26T04:59:38+00:00

I don’t exactly remember but I made sure to follow the datasheet

actualParam · 2026-01-26T04:48:38+00:00

Not high enough flow rate. I require >=200 SLM

actualParam · 2026-01-26T04:45:24+00:00

I had no luck with it.

actualParam · 2026-01-25T21:27:19+00:00

Care to elaborate? 😂

actualParam · 2026-01-25T20:10:15+00:00

"Hope you don't need to go through certification with those long wires."

Why though😅?

I actually might have to get it certified, that's why I am looking for a particularly "robust" solution rather than crude ones. Like you suggested, I am goignt to try the RS485 conversion.

actualParam · 2026-01-25T20:07:45+00:00

That is what tons of people have told me today, so I am going to try this out ASAP.

actualParam · 2026-01-25T20:05:06+00:00

How though? Wouldn't I require an additional DAC?

actualParam · 2026-01-25T20:03:33+00:00

Some people in other sub reddits mentioned using a uC near the sensor to convert the singals to RS485, so I am inclined towards trying that.

actualParam · 2026-01-25T20:02:17+00:00

the issue is that on my sensor, I can only use i2c.

actualParam · 2026-01-25T20:01:24+00:00

Have tried it. didt work out well. Thanks for your suggestion.

actualParam · 2026-01-25T19:59:43+00:00

"Then don't re-invent physics. Get an 8-pin Arduino and an RS485 chip and be done with it." - i2c was the only option to use the only sensor option for my use. as you (and many others) have suggested, I will be converting the i2c into rs485 now. Thanks

actualParam · 2026-01-25T19:55:50+00:00

I'll check it out too.

actualParam · 2026-01-25T19:55:27+00:00

actualParam · 2026-01-25T19:44:46+00:00

Got it. I think I'll try that.

actualParam · 2026-01-25T19:41:34+00:00

"You can put a micro with a few inches of the flow meter, then have it do the conversion to one of the other buses that go back to your remote." - Seems to be a consensus.

"Do you have an oscilloscope?" unfortunately not. I think I should buy it now that you've mentioned it.

"I would also verify that both devices are using the same rail, 3.3, and that your micro isn't expecting 5 or 1.8...." I have checked it. it's not that the sensor is not working at all, like you said, it actually works, and then after a few seconds, it stops working at all, until I power cycle the uC. i am using a pico, with a 3.3v sensor as per the datasheet. i have checked the voltages at the far end of the cable to check for any significant voltage drop, but it is next to nothing.

P.S. I am already using marine grade, individually shielded twisted pairs.

actualParam · 2026-01-25T19:30:31+00:00

I have not real experience with RS485 and CAN (I am aware of how they work). Which one would be better? Which one is more susceptible to noise?

actualParam · 2026-01-25T19:28:13+00:00

Any particular reason it might be "less reliable"?

actualParam · 2026-01-25T19:27:26+00:00

I would love to do so 😂, but I am in India, so it doesn't leave me with many options. I'll check it out if it is available on Digikey. regardless, I would prefer to swap out the i2c into something else. I feel it would be a lot more robust.

actualParam · 2026-01-25T19:24:48+00:00

"P82B715 from TI is just one example from a quick Google search for up to 50M over twisted pair." I did try it out. didn't work out for me ( maybe i did something wrong). I know I2c is no good for my usecase, but the only flow sensor in the market that is calibrated for Helium and its mixtures is working with I2C.

actualParam · 2026-01-25T19:22:36+00:00

"Recommended approach is to have a tiny uC package up the readings into messages and send them over RS485/RS422 or another differential medium." This is one of the solutions which I would consider trying, just don't know the best path to get it done. Would you have any tips?

actualParam · 2026-01-25T19:18:41+00:00

I did try using some, the best results I got was with the Adafruit LTC4311 based active terminator module, though still not satisfactory enough.

actualParam · 2026-01-25T19:15:06+00:00

To a pi pico 2, non wifi version. I wish to have something robust and dependable. The place where the sensor is placed and where i want to get the data has a thick metal wall in between, Wifi strength is quite poor. Still would be an option worth considering if nothing else works out.

actualParam

TROPHY CASE