Controlling a 240V battery charger with a TS-7670 MODBUS 24V switch

mains-ctl.sh

#!/bin/sh

# Controlling the 24V power MOSFETs in the TS-7670
# for 240V solid-state relay control.
#
# © 2025 Stuart Longland VK4MSL

# GPIOs for the various control lines.
# References:
# - https://cdn.embeddedts.com/resource-attachments/ts-7670-schematic.pdf
# - https://github.com/vrtsystems/linux/blob/12f2b9e7ba1014341ea3661939ba220b9d3e05f4/arch/arm/boot/dts/imx28-pinfunc.h
GPIO_3V3=47
GPIO_FAULT=46
GPIO_24V=45

# Battery sensor and thresholds in µV
BATT_VOLTAGE=/sys/class/power_supply/ts-psu/voltage_now
BATT_HIGH=14200000
BATT_LOW=11800000

# To prevent wearing out flash, mount ramfs on /mnt/pwrstatus!
BATT_CHARGED_FILE=/mnt/pwrstatus/fullcharge
BATT_CHARGED_DURATION=300

# The paths to the various sysfs interfaces for GPIO
SYSFS_GPIO_BASE=/sys/class/gpio
SYSFS_GPIO_EXPORT=${SYSFS_GPIO_BASE}/export
SYSFS_GPIO_UNEXPORT=${SYSFS_GPIO_BASE}/unexport
SYSFS_GPIO_3V3_BASE=/sys/class/gpio/gpio${GPIO_3V3}
SYSFS_GPIO_FAULT_BASE=/sys/class/gpio/gpio${GPIO_FAULT}
SYSFS_GPIO_24V_BASE=/sys/class/gpio/gpio${GPIO_24V}

# Initialise GPIOs if not already done
gpio_init() {
	for gpio in \
		${GPIO_3V3} \
		${GPIO_FAULT} \
		${GPIO_24V} ; \
	do
		if [ ! -d ${SYSFS_GPIO_BASE}/gpio${gpio} ]; then
			echo -n ${gpio} > ${SYSFS_GPIO_EXPORT}
			case "${gpio}" in
			${GPIO_3V3})	echo -n out > ${SYSFS_GPIO_3V3_BASE}/direction
					echo -n 1 >  ${SYSFS_GPIO_3V3_BASE}/value
					;;
			${GPIO_24V})	echo -n out > ${SYSFS_GPIO_24V_BASE}/direction
					echo -n 0 >  ${SYSFS_GPIO_24V_BASE}/value
					;;
			${GPIO_FAULT})	echo -n in > ${SYSFS_GPIO_FAULT_BASE}/direction
					;;
			esac
		fi
	done
}

# Read the status of the GPIO pins
read_status() {
	if [ "$( cat "${SYSFS_GPIO_FAULT_BASE}/value" )" != 0 ]; then
		echo fault
	elif [ "$( cat "${SYSFS_GPIO_24V_BASE}/value" )" != 0 ]; then
		echo on
	else
		echo off
	fi
}

# Power everything off
power_off() {
	echo -n 0 > ${SYSFS_GPIO_24V_BASE}/value
	echo -n 1 > ${SYSFS_GPIO_3V3_BASE}/value
}

# Safely power on
power_on() {
	case "$( read_status )" in
	on)	return 0
		;;
	fault)
		return 1
		;;
	esac
	echo -n 0 > ${SYSFS_GPIO_3V3_BASE}/value
	sleep 0.1
	case "$( read_status )" in
	on)	return 0
		;;
	fault)
		power_off
		return 1
		;;
	esac
	echo -n 1 > ${SYSFS_GPIO_24V_BASE}/value
	sleep 1
	case "$( read_status )" in
	on)	return 0
		;;
	*)
		power_off
		return 1
		;;
	esac
}

# Read the raw battery voltage in µV
read_voltage_raw() {
	cat ${BATT_VOLTAGE}
}

# Scale the battery voltage to volts with 3 decimals
scale_voltage() {
	mvolts=$(( ${1} / 1000 ))
	volts=$(( ${mvolts} / 1000 ))
	mvolts=$(( ${mvolts} % 1000 ))
	printf "%d.%03d\n" ${volts} ${mvolts}
}

# Report the battery voltage, scaled to volts
read_voltage_scaled() {
	scale_voltage $( read_voltage_raw )
}

# Return the current time (Unix time)
now() {
	date +%s
}

# Read the time the battery reached charged state
read_charged_time() {
	if [ -f "${BATT_CHARGED_FILE}" ]; then
		cat "${BATT_CHARGED_FILE}"
	else
		echo 0
	fi
}

# Mark the battery as charged now
mark_charged_time() {
	now > "${BATT_CHARGED_FILE}"
}

# Unmark the battery as being charged
unmark_charged_time() {
	rm -f "${BATT_CHARGED_FILE}"
}

# Decide whether mains should be on or not
power_switch_auto() {
	v=$( read_voltage_raw )
	if [ ${v} -gt ${BATT_HIGH} ]; then
		batt_charged=$( read_charged_time )
		if [ "${batt_charged}" = 0 ]; then
			# Just reached charge
			mark_charged_time
			echo "Battery charged, waiting ${BATT_CHARGED_DURATION} seconds"
			scale_voltage ${v}
			return 0
		else
			# Been on long enough.
			case "$( read_status )" in
			on)
				echo "Battery charged, turning mains off"
				scale_voltage ${v}
				power_off
				;;
			fault)
				echo "24V bus fault!!!"
				power_off
				;;
			esac
		fi
	elif [ ${v} -lt ${BATT_LOW} ]; then
		unmark_charged_time
		case "$( read_status )" in
		off)
			echo "Battery low, turning mains on"
			scale_voltage ${v}
			power_on
			;;
		fault)
			echo "24V bus fault!!!"
			power_off
			;;
		esac
	fi
}

# Initialise GPIOs
gpio_init

# Process the command-line argument
case "$1" in
	on)	power_on
		exit $?
		;;
	off)
		power_off
		exit $?
		;;
	auto)
		power_switch_auto
		exit $?
		;;
	*)	read_status
		read_voltage_scaled
		;;
esac