#!/bin/sh
# i2c_keepalive.sh — X6200 AXP PMU keepalive
#
# The X6200 uses an AXP PMU on I2C bus 0, address 0x72.
# Without periodic I2C traffic the unit powers off after ~180s.
# This script sends a combined write+read transaction every second.
#
# Requires: i2c-tools (i2ctransfer)

BUS=0
ADDR=0x72
INTERVAL=1

# Only allow one instance
if pidof -x "$(basename "$0")" >/dev/null 2>&1; then
    COUNT="$(pidof -x "$(basename "$0")" | wc -w)"
    [ "$COUNT" -gt 1 ] && { echo "[keepalive] already running"; exit 0; }
fi

trap 'exit 0' INT TERM

# One-time kick at startup
i2ctransfer -y "$BUS" w4@"$ADDR" 0xFF 0xFE 0x02 0x80 >/dev/null 2>&1
i2ctransfer -y "$BUS" w4@"$ADDR" 0xFF 0xFE 0x03 0x80 >/dev/null 2>&1

# Main keepalive loop
while :; do
    i2ctransfer -y "$BUS" w2@"$ADDR" 0x20 0x00 r1@"$ADDR" >/dev/null 2>&1
    sleep "$INTERVAL"
done