HOW-TOs

Convert a MAC Address to Motorola S-Records

on June 2, 2008

If you do embedded programming you're probably familiar with Motorola S-Records. This following script takes a MAC Address and outputs S-Record data.

Given a MAC Address the script outputs S-Record data:

  # sh macid.sh 00:11:22:33:44:55
  S00D0000333737382D322E746D703B
  S1090000001122334455F7
  S9030000FC

Optionally, you can specify an address for re-basing the S-Record data and an output file name to write the S-Records to:

  # sh macid.sh --address 0xffff0000 --output ma 00:11:22:33:44:55
  # cat ma
  S00D0000333733302D322E746D7047
  S30BFFFF0000001122334455F7
  S705FFFF0000FC

The script follows:

#!/bin/bash

mac_addr_pattern='^[0-9a-fA-F]{2}[-:]'
mac_addr_pattern+='[0-9a-fA-F]{2}[-:]'
mac_addr_pattern+='[0-9a-fA-F]{2}[-:]'
mac_addr_pattern+='[0-9a-fA-F]{2}[-:]'
mac_addr_pattern+='[0-9a-fA-F]{2}[-:]'
mac_addr_pattern+='[0-9a-fA-F]{2}'

address_pattern='^(0x)?[0-9a-fA-F]{8}$'


######################################################################
function usage()
{
    if [[ "$*" ]]; then echo $* >&2; fi
    cat >&2 <<EOU
Usage: $0 OPTIONS MAC-ADDRESS
  --address ADDRESS              Address in FLASH of serial number or MAC Id.
  --output FILE                  Output file.
EOU
    exit 1
}


######################################################################
trap "rm -f $$-?.tmp" EXIT

output_file=

while [[ "$1" ]]
do
    case "$1" in
    --address)
        shift
        if [[ ! "$1" ]]; then usage "Missing address"; fi
        address=$1
        if ! grep --silent -P "$address_pattern" <<<$address; then
            usage "Invalid address: $address"
        fi
        ;;
    --output)
        shift
        if [[ ! "$1" ]]; then usage "Missing output file name"; fi
        output_file=$1
        ;;
    *)
        mac_addr=$1
        shift
        if [[ "$1" ]]; then usage "Unexpected argument: $1"; fi
        if ! grep --silent -P "$mac_addr_pattern" <<<$mac_addr; then
            usage "Invalid mac address: $mac_addr"
        fi
        ;;
    esac
    shift
done

if [[ ! "$mac_addr" ]]; then usage "Missing mac address"; fi

mac_addr=${mac_addr/:/ }
mac_addr=${mac_addr/-/ }
echo "0000: $mac_addr" | xxd -r >$$-1.tmp
opt=
if [[ "$address" ]]; then opt="--change-addresses $address"; fi
objcopy $opt -I binary -O srec $$-1.tmp $$-2.tmp
if [[ "$output_file" ]]; then
    mv $$-2.tmp $output_file
else
    cat $$-2.tmp
fi

# vim: tabstop=4: shiftwidth=4: noexpandtab:
# kate: tab-width 4; indent-width 4; replace-tabs false;

Mitch Frazier is an embedded systems programmer at Emerson Electric Co. Mitch has been a contributor to and a friend of Linux Journal since the early 2000s.

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HOW-TOs

Convert a MAC Address to Motorola S-Records

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