Basic relay control ash script

RelayAndGPIOModules/USBRelayAndGPIOModules/sh/usbrelay1_2_4_8/numato.sh

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+#!/bin/sh
+#
+# This code is published and shared under GNU LGPL
+# license with the hope that it may be useful. Read complete license at
+# http://www.gnu.org/licenses/lgpl.html or write to Free Software Foundation,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
+#
+# Simplicity and understandability is the primary philosophy followed while
+# writing this code. Sometimes at the expense of standard coding practices and
+# best practices. It is your responsibility to independantly assess and implement
+# coding practices that will satisfy safety and security necessary for your final
+# application.
+#
+# This demo code demonstrates how to turn on/off a relay
+#
+
+VID=2a19
+PID=0c05
+
+help() {
+	echo "Usage: numato.sh <relay number> <on|off>"
+	echo example: ./numato.sh 0 on
+	exit 1
+}
+
+# find tty relating to given pid and vid
+# return after first tty device found
+findtty() {
+	local TTY=
+	local idVendor=$1
+	local idProduct=$2
+	local usb_devs="$(grep -l $idVendor /sys/bus/usb/devices/*/idVendor)"
+
+	for usbdev in $usb_devs
+	do
+		usbdev=$(dirname $usbdev)
+		if [ "$(cat $usbdev/idProduct)" = "$idProduct" ]
+		then
+			TTY=/dev/$(basename $usbdev/*1.0/tty/*)
+			[ -n $TTY ] && echo $TTY && return
+		fi
+	done
+}
+
+ret=1
+response='\n'
+file="/tmp/numato.$$"
+
+[ "$1" = "" ] && help
+num=$1
+
+[ "$2" = "" ] && help
+cmd=$2
+
+case "$cmd" in
+on) cmd=on ;;
+off) cmd=off ;;
+*) help ;; 
+esac
+
+TTY=$(findtty $VID $PID)
+[ -z "$TTY" ] && echo "Could not find TTY" && exit 1
+
+stty -F $TTY 19200 -echo -echoe -echok -opost -icanon -inlcr
+chat -V -t 1 "" "relay ${cmd} ${num}\r\n" "$response" < "$TTY" > "$TTY" 2> $file
+
+[ -s $file ] && ret=0
+rm -rf $file
+
+if [ $ret = 0 ]; then
+	echo "Powered relay ${num} ${cmd}"
+else
+	echo "Failed to set relay ${num} ${cmd}"
+fi
+
+exit $ret
+