RaspberryPi3B crashes randomly

Question

I've a RaspberryPi 3 B running with Raspian on buster (10).

Hardware:

• Power: Official 5.1 V - 2.5 A Power Supply (https://www.raspberrypi.com/products/raspberry-pi-universal-power-supply/)
• Wired Ethernet Connection
• No WiFi, no Bluetooth in use
• USB FlashDrive
• USB ConBee II Zigbee Adapter
• Headless setup with node-red, ziigbee2mqtt, pi-hole and some other services

With that configuration, the system has worked well for several years (!) without any issues apart from 2 SD-card errors.

Some weeks ago, I've added an adaptor with realtek rtl2832u to fetch 433 MHz data. Therefore, I've installed rtl_sdr which pushes 433-Mhz weather-station data to zigbee. In general, this works well, but now, I'm facing sudden crashes of the Raspi.

Crash means:

• Device can be ping'ed
• no ssh connection (timeout)
• no other server connection
• no zigbee communicaton
• a connection via hdmi doesn't show anything

Only solution is to unplugg power supply.

I've checked

• dmesg
• /var/log/kern.log
• /var/log/messages
• /var/log/syslog

Without finding anything. Additionally I can't find any sign of undervoltage, in particular:

pi@raspberrypi:~ $ vcgencmd get_throttled
throttled=0x0

The crash happens after some hours or a week. When unplugging the rtl2832u, everything runs smoothly again.

How shall I investigate this further?

• Powered USB-hub? (Which devices to be connected to this, which directly to the Raspi?, USB 3.0 recommended?)
• other power supply?
• moving zigbee stick and rtl-stick further away (~10 cm)
• anything else?

Update 2022-03-22

With open housing systems runs now for 26 h without any issue. Temperature is mostly between 50 and 60 deg celcius with rare spikes up to 62 deg.

Memory

pi@raspberrypi:~ $ free -m
              total        used        free      shared  buff/cache   available
Mem:            923         387          71           3         463         479
Swap:         59330         335       58995

Is there anything bad with theses numbers?

Update 2022-04-02

I've added an active usb hub to power the sdr-device. Unfortunately, the crash happend again after 3 days. :-(

Now, I'm wondering whether the issue has actually no causality with adding the stick but with re-arranging my devices (power adaptors, network switch, raspi) within a cable box. Therefore, I've removed the switch from the box (which was the case before adding the sdr-stick) as well as the sdr-stick and the active usb hub. In other words, it's almost the same setup as before.

Now, I'll see if it crashes again. If not, I'll add the sdr stick once again.

Update 2022-04-07 After 5 days of operation I see this memory usage

pi@raspberrypi:~ $ free -m
              total        used        free      shared  buff/cache   available
Mem:            923         460         115          38         347         376
Swap:            99          99           0

I don't get why total swap changes from last check. available mem slightly decreased.

I've logged temperature and cpu load in node-red:

Now, I've plugged the sdr-stick into the pi, without starting any further software and will monitor this for several days.

Update 2022-04-08

I didn't change anything on swap.

pi@raspberrypi:~ $ cat /proc/swaps
Filename                                Type            Size            Used            Priority
/var/swap                               file            102396          102296          -2

This matches to the configuration in /etc/dphys-swapfile which contains

CONF_SWAPSIZE=100

Answer 1

Update 2022-04-16

After 4 days with complete setup including sdr-stick, I've seen no crash anymore. My guess is, that the crash was an EMC issue, which has been solved by moving a network switch including power supply from the raspi.

Memory as of today:

pi@raspberrypi:~ $ free -h
              total        used        free      shared  buff/cache   available
Mem:          923Mi       495Mi        70Mi        54Mi       357Mi       319Mi
Swap:          99Mi        99Mi       0.0Ki

I've seen values between 300 and 400 MiB when checking.

Thanks for all comments which helped me on that way.