Is node-red causing this i2c problem

General
1

Hi - I wonder if anyone can offer any insight into this problem?

Pi 4B, Raspbian 10 (buster)
From a fresh reboot
i2cdetect -y 1 (see pic)
Start Node-Red (and do nothing else - I don't have any i2c nodes installed)
i2cdetect - y 1 (second half of the pic)

image
image947×763 207 KB

It seems Node-Red is ? corrupting the bus maybe

I have a python scrip that interacts with the i2c bus - works before I start Node-Red but won't work afterwards.

I'm also unable to stop Node-Red from the command line
node-red-stop
Just sits there having made no apparent change (browser page still works)

Likewise
node-red-log doesn't do anything either.

I've been unable to get the i2c nodes to work at all in Node_Red

I suspect I have stuffed up the node-red installation somewhere.

Any advice appreciated.

2

Some ideas here:

3

How did you install node-red? The recommended method is described at https://nodered.org/docs/getting-started/raspberrypi. If you did not do that then I recommend running the script, it will ensure you have a consistent set of tools. It should not be necessary to uninstall anything first (assuming you have not done anything too unusual) and it should not overwrite your existing flows, though if they are important then no doubt you have a backup anyway.

If you did do that how are you starting node-red?
Also what do you see in the terminal if you run

node-red-stop
node-red-start

Use the </> button to paste the text in.

4

Ok - good progress. I started with a completely fresh SD card (buster)
updated everything as standard
ran i2cdetect and found all 4 parts
started node-red
ran i2cdetect again - same 4 parts found (this is where is went wrong origionally)
ran the browser with a simple i2cscan node

and that produced the expected results
All I need to do now is figure out how to actually communicate with these parts :slight_smile:

Thanks for your help - I'll post my progress for future reference in case anyone else runs into the same problem.

5

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