ds1307.py

if __name__ == "__main__":
    from datetime import datetime, timedelta
    from smbus import SMBus
    from sys import argv
    from time import sleep

    argc = len(argv)
    bus = SMBus(1 if argc < 2 else int(argv[1]))
    rop = "r" if argc < 3 else argv[2].lower()[0:1]

    bcd2bin = lambda n: n - 6 * (n >> 4)

    if rop == "r":
        print(bus.read_i2c_block_data(0x68, 0x00, 7))

    if rop == "w":
        now = datetime.utcnow()
        print(now)
        sleep(1 - now.microsecond / 1e6)  # TODO: review!!!
        now += timedelta(0, 1)
        print(now)
        bus.write_i2c_block_data(
            0x68,
            0x00,
            [
                n + 6 * (n // 10)
                for n in (
                    now.second,
                    now.minute,
                    now.hour,
                    now.isoweekday(),
                    now.day,
                    now.month,
                    now.year - 2000,
                )
            ],
        )

ds1307.sh

#!/bin/sh

# shellcheck enable=all disable=SC2046,SC2086,SC2250

do_read() {
	! res=$(i2cget -y $bus 0x68 0x00 i 7 2>/dev/null) && exit 2
	set -- $(for v in $res; do printf '%d ' $((v - 6 * (v >> 4))); done)
	fmt='%F %T %z'
	date --date="$6/$5/20$7 $3:$2:$1 Z" +"$fmt" # TODO: don't assume 2k
	date +"$fmt"
}

do_write() {
	# TODO: wait until next second
	res=$(date -u +'%-S %-M %-H %u %-d %-m %-y' 2>/dev/null) # TODO: avoid GNU
	set -- $(for v in $res; do printf '0x%02x ' $((v + 6 * (v / 10))); done)
	! i2cset -y $bus 0x68 0x00 $1 $2 $3 $4 $5 $6 $7 i 2>/dev/null && exit 3
}

do_sync() {
	do_write
	do_read
}

main() {
	bus=${1:-1}
	case ${2:-r} in
	r*) do_read ;;
	w*) do_write ;;
	s*) do_sync ;;
	*) exit 1 ;;
	esac
}

main "$@"