[JetKVM][ATX Power Extension] shell script to power on PC

atx_power_on.sh

#!/usr/bin/env sh

# ATX Power Control Extension Board Peripheral
SERIAL_DEV=/dev/ttyS3

# Since the extension board provides power to the jetkvm,
# we can assume the extension is connected over serial.

check_atx_status() {
    ATX_STATUS=$((2#$(head -n1 $SERIAL_DEV)))
    # Evaluate each bit to active-high state
    HDD_LED_STATE=$((($ATX_STATUS & 2#1000) == 0))
    PWR_LED_STATE=$((($ATX_STATUS & 2#0100) == 0))
    RST_BTN_STATE=$((($ATX_STATUS & 2#0010) > 0))
    PWR_BTN_STATE=$((($ATX_STATUS & 2#0001) > 0))
    #echo "atx_status=$ATX_STATUS"
}

check_atx_status

if [ $PWR_LED_STATE -eq 0 ]; then
    # Release power/reset buttons
    printf 'BTN_RST_OFF\n\n' > $SERIAL_DEV
    printf 'BTN_PWR_OFF\n\n' > $SERIAL_DEV
    sleep 1
    check_atx_status

    echo "Turning PC on..."
    printf 'BTN_PWR_ON\n\n' > $SERIAL_DEV
    sleep 1.5
    printf 'BTN_PWR_OFF\n\n' > $SERIAL_DEV

    # check power status
    sleep 1.5
    check_atx_status

    # return 0 if PC is on and 1 otherwise
    return $((!$PWR_LED_STATE))
fi

echo "PC already on"
return 0