Updated Elro TXP script

#!/bin/bash
set -euo pipefail

#######################################
# Builds a TXP string from the given arguments
# Globals:
#   None
# Arguments:
#   $masterCode $slaveCode $stateCode
# Returns:
#   $msgStr
#######################################
build_elro_txp() {
  local masterCode=$1
  local slaveCode=$2
  local stateCode=$3

  local sA=0
  local sG=0
  local sRepeat=15
  local sPause=5600
  local sTune=350
  local sBaud=25
  local sSpeed=16

  local headStr="TXP:$sA,$sG,$sRepeat,$sPause,$sTune,$sBaud,"
  local tailStr=",1,1,$sSpeed,;"
  local onStr="1,3,1,3,3"
  local offStr="3,1,1,3,1"

  local bitLow=1
  local bitHgh=3

  local seqLow="$bitHgh,$bitHgh,$bitLow,$bitLow,"
  local seqHgh="$bitHgh,$bitLow,$bitHgh,$bitLow,"

  local msg=""
  local bits=$masterCode$slaveCode
  for (( i=0; i<${#bits}; i++ ))
  do
    local bit=${bits:$i:1}

    if [ "$bit" == "0" ]; then
      local msg=$msg$seqLow
    else
      local msg=$msg$seqHgh
    fi
  done


  if [ "${stateCode,,}" == "on" ]; then
    local stateCode=$onStr
  fi
  if [ "${stateCode,,}" == "off" ]; then
    local stateCode=$offStr
  fi

  local msgStr=$headStr$bitLow","$msg$bitHgh","$stateCode$tailStr
  echo "$msgStr"
}

err() {
  echo -e "[$(date +'%Y-%m-%dT%H:%M:%S%z')]: $*" >&2
  exit 1
}

# main
if [ "$#" -lt 3 ]; then
  err "Wrong number of arguments $# ($*).\nUsage: $0 <masterdip> <slavedip> on|off"
fi

masterCode=$1
slaveCode=$2
stateCode=$3

if [ "${#masterCode}" -ne 5 ]; then
    err "Master code has to contain 5 digits."
fi
if [ "${#slaveCode}" -ne 5 ]; then
    err "Slave code has to contain 5 digits."
fi
if [[ "$masterCode" = *[^0-1]* ]] || [[ "$slaveCode" = *[^0-1]* ]]; then
    err "Master and slave code can only contain 0 and 1."
fi
if [ "${stateCode,,}" != "on" ] && [ "${stateCode,,}" != "off" ]; then
    err "Unknown state ${stateCode}."
fi

string=$(build_elro_txp "$masterCode" "$slaveCode" "$stateCode")
echo "$string"
exit