Radxa Cubie A7A hardware control scripts and systemd services (fan control, CPU LED, power button)

cpu-led.service

[Unit]
Description=CPU Activity LED
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/local/bin/cpu-led.sh
Restart=always
RestartSec=5

[Install]
WantedBy=multi-user.target

cpu-led.sh

#!/bin/bash
# Blink LED based on CPU activity - faster blinks = higher load
set -euo pipefail

LED="/sys/class/leds/radxa:blue:user/brightness"

# Verify LED device exists
if [[ ! -w "$LED" ]]; then
    echo "ERROR: LED device not found or not writable: $LED" >&2
    exit 1
fi

PREV_IDLE=0
PREV_TOTAL=0

while true; do
    # Read CPU stats
    read -r cpu user nice system idle iowait irq softirq _ < /proc/stat
    TOTAL=$((user + nice + system + idle + iowait + irq + softirq))
    IDLE=$idle

    # Calculate usage since last sample
    DIFF_IDLE=$((IDLE - PREV_IDLE))
    DIFF_TOTAL=$((TOTAL - PREV_TOTAL))

    if [ $DIFF_TOTAL -gt 0 ]; then
        USAGE=$((100 * (DIFF_TOTAL - DIFF_IDLE) / DIFF_TOTAL))
    else
        USAGE=0
    fi

    PREV_IDLE=$IDLE
    PREV_TOTAL=$TOTAL

    # Blink pattern based on load (higher load = more on time)
    if [ $USAGE -gt 5 ]; then
        echo 1 > $LED
        # On time proportional to load (10-100ms)
        sleep $(awk "BEGIN {printf \"%.2f\", $USAGE / 1000 + 0.01}")
        echo 0 > $LED
        # Off time inversely proportional (faster blinks at high load)
        sleep $(awk "BEGIN {printf \"%.2f\", (100 - $USAGE) / 1000 + 0.02}")
    else
        # Idle: LED off, slow poll
        echo 0 > $LED
        sleep 0.2
    fi
done

fan-control.service

[Unit]
Description=Fan Control Service
After=multi-user.target

[Service]
Type=simple
ExecStart=/usr/local/bin/fan-control.sh
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

fan-control.sh

#!/bin/bash
# Fan control based on maximum junction temperature across all zones
# A733 specs: Tj max recommended 115°C, absolute 125°C
set -euo pipefail

COOLING_DEVICE="/sys/class/thermal/cooling_device2/cur_state"

# Verify cooling device exists
if [[ ! -w "$COOLING_DEVICE" ]]; then
    echo "ERROR: Cooling device not found or not writable: $COOLING_DEVICE" >&2
    exit 1
fi

# Thermal zones to monitor (CPU, GPU, NPU, DDR)
ZONES=(
    "/sys/class/thermal/thermal_zone0/temp"   # cpul
    "/sys/class/thermal/thermal_zone1/temp"   # cpub
    "/sys/class/thermal/thermal_zone4/temp"   # gpu
    "/sys/class/thermal/thermal_zone5/temp"   # npu
    "/sys/class/thermal/thermal_zone6/temp"   # ddr
)

# Temperature thresholds (millidegrees Celsius)
# Kernel throttle points: 70°C (throttle), 90°C (heavy), 110°C (crit/shutdown)
# Fan curve is aggressive to prevent throttling
TEMP_OFF=45000      # Below 45°C: fan off
TEMP_LOW=55000      # 45-55°C: state 1 (low) - stay ahead of throttle
TEMP_MED=65000      # 55-65°C: state 2 (medium) - before 70°C throttle
TEMP_HIGH=75000     # 65-75°C: state 3 (high) - throttle mitigation
                    # Above 75°C: state 4 (max) - well before 90°C heavy throttle

get_max_temp() {
    local max=0
    for zone in "${ZONES[@]}"; do
        temp=$(cat "$zone" 2>/dev/null || echo 0)
        if [ "$temp" -gt "$max" ]; then
            max=$temp
        fi
    done
    echo $max
}

while true; do
    TEMP=$(get_max_temp)

    if [ "$TEMP" -lt "$TEMP_OFF" ]; then
        STATE=0
    elif [ "$TEMP" -lt "$TEMP_LOW" ]; then
        STATE=1
    elif [ "$TEMP" -lt "$TEMP_MED" ]; then
        STATE=2
    elif [ "$TEMP" -lt "$TEMP_HIGH" ]; then
        STATE=3
    else
        STATE=4
    fi

    echo $STATE > $COOLING_DEVICE
    sleep 5
done

power-button-event

event=button/power.*
action=/etc/acpi/power-button.sh %e

power-button.sh

#!/bin/bash
# Power button = graceful reboot
# For shutdown, use SSH: sudo shutdown -h now
logger "Power button pressed - rebooting"
/sbin/shutdown -r now

Radxa Cubie A7A Hardware Control Scripts.md

Radxa Cubie A7A Hardware Control Scripts

Scripts and systemd services for fan control, CPU activity LED, and power button handling on the Radxa Cubie A7A.

Fan Control

Temperature-based fan speed control monitoring CPU, GPU, NPU, and DDR thermal zones.

1. Copy files to the system:

sudo cp fan-control.sh /usr/local/bin/fan-control.sh
sudo chmod 755 /usr/local/bin/fan-control.sh
sudo cp fan-control.service /etc/systemd/system/fan-control.service

2. Enable and start:

sudo systemctl daemon-reload
sudo systemctl enable fan-control.service
sudo systemctl start fan-control.service

3. Verify:

systemctl status fan-control.service
cat /sys/class/thermal/cooling_device2/cur_state

---

CPU Activity LED

Blinks the blue user LED based on real CPU utilization (faster blinks = higher load).

1. Set LED to manual control:

sudo sh -c 'echo none > /sys/class/leds/radxa:blue:user/trigger'

2. Copy files to the system:

sudo cp cpu-led.sh /usr/local/bin/cpu-led.sh
sudo chmod 755 /usr/local/bin/cpu-led.sh
sudo cp cpu-led.service /etc/systemd/system/cpu-led.service

3. Enable and start:

sudo systemctl daemon-reload
sudo systemctl enable cpu-led.service
sudo systemctl start cpu-led.service

4. Verify:

systemctl status cpu-led.service

---

Power Button (Reboot on Press)

By default, systemd-logind handles the power button and will shut down the system. These instructions configure acpid to handle the power button instead, triggering a graceful reboot.

1. Install acpid:

sudo apt install -y acpid

2. Tell systemd-logind to ignore the power button:

sudo sed -i 's/#HandlePowerKey=.*/HandlePowerKey=ignore/' /etc/systemd/logind.conf
grep -q "^HandlePowerKey" /etc/systemd/logind.conf || echo "HandlePowerKey=ignore" | sudo tee -a /etc/systemd/logind.conf
sudo systemctl restart systemd-logind

3. Copy files to the system:

sudo cp power-button.sh /etc/acpi/power-button.sh
sudo chmod 755 /etc/acpi/power-button.sh
sudo cp power-button-event /etc/acpi/events/power-button

4. Enable and restart acpid:

sudo systemctl enable acpid
sudo systemctl restart acpid

5. Test by pressing the power button - system should reboot (not shutdown).

Note: To shutdown instead of reboot, use SSH: sudo shutdown -h now