1 files changed, 67 insertions, 0 deletions
diff --git a/misc/relayctl b/misc/relayctl
new file mode 100755
index 0000000..b356031
--- /dev/null
+++ b/misc/relayctl
@@ -0,0 +1,67 @@
+#!/bin/sh
+
+# setup
+set -e
+die() { echo "usage: $0 [-r relay] [-s state] [-ght] [device]" && exit $1 ; }
+
+getstate() {
+	tty=$1
+	relay=${2:-1}
+
+	# write 0xFF for status
+	printf '\377' > $tty
+
+	# read status response for selected relay
+	while read r; do case "$r" in "CH${relay}: "*) echo "$r" && return ;; esac; done < $tty
+}
+
+genbytes() {
+	# the relay is controled by a fixed 4 byte command as follows:
+	start=160  # always 0xA0
+	relay=$1   # relay id (counts from 1)
+	state=$2   # whether to energize 1 or 0
+	checksum=$(( start + relay + state ))  # checksum is just a sum
+
+	# generate the octal sequence with printf, then convert to bytes with printf again
+	printf "$(printf '\\%03o\\%03o\\%03o\\%03o' $start $relay $state $checksum)"
+}
+
+# args
+relay=1
+state=1
+
+while getopts 'r:s:ght' opt; do
+	case "$opt" in
+		r) relay="$OPTARG" ;;
+		s) state="$OPTARG" ;;
+		g) get=1 ;;
+		t) get=1 && toggle=1 ;;
+		h) die 0 ;;
+		\?) die 1 ;;
+	esac
+done
+
+shift $((OPTIND - 1))  # shift to final arg
+tty="${1:-/dev/stdout}"  # output to stdout as fallback
+
+# validate
+case $relay in [1-9]|[1-9][0-9]*) ;; *) die 1 ;; esac
+case $state in [01]) ;; *) die 1 ;; esac
+[ -n "$get" ] && [ "$tty" = "/dev/stdout" ] && die 1
+
+# handle get commands
+if [ -n "$get" ]; then
+	s=$(getstate "$tty" $relay) || die 1
+
+	if [ -z "$toggle" ]; then
+		echo "$s" && exit 0 # exit when no toggle
+	else
+		case "$s" in
+			*ON)  state=0 ;;
+			*OFF) state=1 ;;
+		esac
+	fi
+fi
+
+# go
+genbytes $relay $state > "$tty"