Print raw steno output from a serial input device

steno_raw.sh

#!/bin/bash
set -e

declare -a RAW_OUTPUT=()
declare -A STENO_HEX=(
   ['a00000000000']='#,1'
   ['900000000000']='#,1'
   ['800000000020']='#,1'
   ['840000000000']='#,1'

   ['804000000000']='S,2'
   ['802000000000']='S,2'
   ['801000000000']='T,3' 
   ['800800000000']='K,4' 
   ['800400000000']='P,5' 
   ['800200000000']='W,6' 
   ['800100000000']='H,7' 
   ['800040000000']='R,8' 

   ['800020000000']='A,9' 
   ['800010000000']='O,10' 

   ['800008000000']='*,11'
   ['800004000000']='*,11'
   ['800000200000']='*,11'
   ['800000100000']='*,11'

   ['800000080000']='E,12' 
   ['800000040000']='U,13' 

   ['800000020000']='F,14' 
   ['800000010000']='R,15' 
   ['800000004000']='P,16' 
   ['800000002000']='B,17' 
   ['800000001000']='L,18' 
   ['800000000800']='G,19' 
   ['800000000400']='T,20' 
   ['800000000200']='S,21' 
   ['800000000100']='D,22' 
   ['800000000001']='Z,23' 
)

stty -F /dev/ttyACM0 9600
stty -F /dev/ttyACM0 raw

stdbuf --output=0 \
   xxd -ps -c6 /dev/ttyACM0 \
| while read -r input ; do
   if (( (0x$input & 0x800000000000) != 0x800000000000 )) ; then
      printf '(UNEXPECTED MSB: %s)\n' "$input"
      exit 1
   fi

   for i in {1..23} ; do
      RAW_OUTPUT[i]=" "
   done

   declare -i match=0
   for letter in "${!STENO_HEX[@]}" ; do
      if (( (0x$input & 0x$letter) == 0x$letter )) ; then
         IFS=, read -r output position <<< "${STENO_HEX[$letter]}"
         RAW_OUTPUT[position]="$output"
         match=1
      fi
   done

   if (( match )) ; then
      printf '%s' "${RAW_OUTPUT[@]}"
      printf '\n'
   else
      printf '(NO MATCH: %s)\n' "$input"
   fi
done