When /node/ has step count /c/ {
  if {[expr {int($c) % 1000}] == 0} {
    set currentTimeMillis [clock milliseconds]
    set millisSinceMinuteStart [expr {$currentTimeMillis % 60000}]
    set fillValue [expr {$millisSinceMinuteStart * 64 / 60000}]

    set matrixportaloutput ""
    for {set y 0} {$y < 32} {incr y} {
      for {set x 0} {$x < 64} {incr x} {
        if {$x < $fillValue} {
          set matrixportaloutput "9$matrixportaloutput"
        } else {
          set matrixportaloutput "0$matrixportaloutput"
        }
      }
    }
    set c [clock milliseconds]
    Wish MQTT publish "$matrixportaloutput" on topic /home/matrixportal at timestamp $currentTimeMillis
  }
}