#!/bin/bash
# Sends a Set Target command to a Pololu Maestro servo controller
#
# O L D Doc:
#
# Usage: maestro-set-target.sh DEVICE CHANNEL TARGET
# Linux example: bash maestro-set-target.sh /dev/ttyACM0 0 6000
# Mac OS X example: bash maestro-set-target.sh /dev/cu.usbmodem00234567 0 6000
# Windows example: bash maestro-set-target.sh '\\.\USBSER000' 0 6000
# Windows example: bash maestro-set-target.sh '\\.\COM6' 0 6000
# CHANNEL is the channel number
# TARGET is the target in units of quarter microseconds.
# The Maestro must be configured to be in USB Dual Port mode.
#
# N E W Doc:
#
# ./stepper_moto.sh /dev/ttyACM0 0
#
DEVICE=$1
CHANNEL=$2
DIRECTION=$(echo $RANDOM % 2 + 1 | bc)
let DIRECTION=$DIRECTION-1
byte() {
  printf "\\x$(printf "%x" $1)"
}
i=4
if [ "${DIRECTION}" -eq 0 ]; then
    TARGET=4000
else
    TARGET=9000
fi
COUNT=$(echo $RANDOM % 4 + 1 | bc)
while [ "$COUNT" -gt 0 ]
do
	{
	byte 0x84
	byte $CHANNEL
	byte $((TARGET & 0x7F))
	byte $((TARGET >> 7 & 0x7F))
	} > $DEVICE
	if [ "${DIRECTION}" -eq 0 ]; then
		TARGET=$(($TARGET+1000))
	else
		TARGET=$(($TARGET-1000))
	fi
	COUNT=$(($COUNT-1))
	sleep 1
	echo " COUNT $COUNT DIRECTION $DIRECTION TARGET $TARGET "
done