surveillance-temperature.sh
With zero dependencies, this script reads the thermal sensor exposed by the Linux kernel, logs CPU temperature and frequency to CSV and prints an alert past a threshold. Perfect to size passive cooling.
Hardware required
A BeaglePlay (TI AM625) on the official Debian image, powered by 5 V/3 A USB-C, with its mikroBUS socket, Grove connector and five user LEDs. None: the board measures its own temperature (SoC sensor).
Wiring
No wiring. Check /sys/class/thermal/thermal_zone*/temp exists (otherwise load the SoC thermal module).
How it works
The kernel exposes temperature in milli-°C in sysfs; the script converts it, compares with the threshold and appends a timestamped CSV line. The current frequency confirms thermal throttling. On Debian: the five user LEDs (USR0-4) are driven by gpio-leds with triggers (heartbeat, disk…); for raw I/O use libgpiod (gpiochip0) on a free mikroBUS line.
Going further
Add forced cooling (pwm-fan in sysfs), or push the CSV to a server with curl in the same cron.
surveillance-temperature.sh
#!/bin/bash
# Surveillance thermique : /sys/class/thermal + journalisation + alerte.
# Aucune dependance : sysfs et bash uniquement.
SEUIL_C="${SEUIL_C:-70}" # degres avant alerte (variable d'env)
INTERVALLE="${INTERVALLE:-5}" # secondes entre deux mesures
JOURNAL="${JOURNAL:-/tmp/cpu-temp.csv}"
[ -f "$JOURNAL" ] || echo "horodatage,temp_c,frequence_mhz" > "$JOURNAL"
# Premier capteur thermique expose par le noyau (varie selon la carte)
ZONE=$(ls /sys/class/thermal/ | grep ^thermal_zone | head -1)
[ -n "$ZONE" ] || { echo "aucun capteur thermique dans /sys/class/thermal"; exit 1; }
echo "Capteur : $ZONE"
while true; do
TEMP=$(($(cat /sys/class/thermal/$ZONE/temp) / 1000)) # milli-C -> C
FREQ=$(awk 'NR==1{print $1/1000}' \
/sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq 2>/dev/null || echo 0)
TS=$(date -Is)
echo "$TS,$TEMP,$FREQ" >> "$JOURNAL"
if [ "$TEMP" -ge "$SEUIL_C" ]; then
echo "$(date +%T) ALERTE : ${TEMP}C >= ${SEUIL_C}C (freq ${FREQ} MHz)"
else
echo "$(date +%T) temp ${TEMP}C freq ${FREQ}MHz"
fi
sleep "$INTERVALLE"
done