journal-cron.sh
The cron + short-script pair is Linux' universal scheduler: every minute, CPU load and temperature are appended to a CSV with built-in rotation. Zero dependencies, zero daemons, survives reboots on its own.
Hardware
An Orange Pi 5 Plus (Rockchip RK3588, 4 Cortex-A76 + 4 Cortex-A55, up to 16 GB RAM) running Armbian/Debian, 40-pin GPIO header and dual gigabit Ethernet. None: readings come from the board itself.
Wiring
No wiring. Check cron (or cronie) is installed and running on the distribution you use.
How it works
cron runs the script on schedule; the script reads /proc and sysfs, appends a CSV line then truncates past 100,000 lines to bound storage.
Running it
Flash Armbian for RK3588, then sudo apt install python3-gpiod gpiod. Find the chip with gpiodetect and pins with gpioinfo, adapt the script and run it (python3 or ./script.sh).
Variants
Push the CSV to a server (curl -T), or replace cron with a systemd timer (OnUnitActiveSec=60) for integrated journalctl logs.
journal-cron.sh
#!/bin/bash
# Mesure ponctuelle appelee par cron (ici toutes les minutes).
# Installation :
# sudo cp journal-cron.sh /usr/local/bin/mesure-cart.sh
# sudo chmod +x /usr/local/bin/mesure-cart.sh
# (crontab -e) puis : * * * * * /usr/local/bin/mesure-cart.sh
JOURNAL="/var/log/mesure-cart.csv"
[ -f "$JOURNAL" ] || echo "horodatage,charge,temp_c" > "$JOURNAL"
# 1) Charge moyenne (1 minute) depuis /proc/loadavg
CHARGE=$(awk '{print $1}' /proc/loadavg)
# 2) Temperature SoC (tolere l'absence du capteur)
TEMP="NA"
for z in /sys/class/thermal/thermal_zone*/temp; do
[ -r "$z" ] && TEMP=$(( $(cat "$z") / 1000 )) && break
done
# 3) Ligne CSV horodatee, append atomique
echo "$(date -Is),$CHARGE,$TEMP" >> "$JOURNAL"
# 4) Rotation maison : garder ~100 000 lignes (~70 jours a la minute)
if [ "$(wc -l < "$JOURNAL")" -gt 100000 ]; then
tail -n 50000 "$JOURNAL" > "$JOURNAL.tmp" && mv "$JOURNAL.tmp" "$JOURNAL"
fi