[LEDE-DEV] Serial data getting lost - bug or a feature?

[Valent Turkovic]

Hi,
I'm working with Lede on ar71xx platform (Carambola2 wifi module) to
gather sensor data over serial, save it and transfer it to "could".

Previous firmware was based on OpenWrt Chaos Calmer but latest one is
based upon Lede 17.01.01. I'll test it also with 17.01.03 soon.

What I have discovered is that now with using Lede sometimes there are
missing characters while reading data from serial connection.

Data is not constantly being read, but sensor device is logging data
usually for 8 hours and then data is read via serial in one big
"download". During these downloads I have never seen a character go
missing while Chaos Calmer was used.

What was even stranger is that sometimes I did get these "bad logs"
(ie ones with few missing characters) but sometimes log download went
perfectly!

After some head scratching and troubleshooting I managed to reproduce
this "bug" 100% and it was due to wifi! But only if wifi was enabled
and not being used!

So if radio was enabled, in sta mode but not connected to AP errors
would happen! It I would disable wifi or if radio was associated with
AP then there would be no errors during reading data from serial
connection.

Is there any explanation for this behaviour? Is this a bug or a
feature? Is there any change between OpenWrt CC version and Lede that
could explain this?

Thanks in advance for any insight and answers,
Valent.