Linked from: https://karma-laboratory.com/petridish/2005/04/wp_part_vii_bs2.html.

'{$STAMP BS2sx}
'{$PBASIC 2.5}

'Author: Pearl Chen (pearl at karma-laboratory.com)
'Date: Mar 8, 2004
'Revisions: put SERIN in the loop (using a counter now instead of FOR...NEXT)
'           which replaces PAUSE so the animation will refresh more often


'***** PINS *****
'Columns (negative / anode) 1 through 8 are pins 8 through 15 respectively
'Rows (positive / cathode) A through H are pins 0 through 7


'***** CONSTANTS ******
P            CON      2        'Pause length for how long a row stays lit up
Baudmode     CON      0        'Baudmode for BS2sx @ 125000 bps
SerialPin    CON      16       'Pin 16 is the dedicated serial I/O pin on my Stamp


'***** VARIABLES *******
col     VAR        Byte(8)     'col will be a decimal number coming in from Processing to turn on pins 0-7
row     VAR        Byte        'row will be used as a counter to turn on the pins 8-15

'***** INIT *******
Init:
  DIRS = %1111111111111111       'Set the direction of all pins to output
  OUTS = %0000000000000000       'Init all pins to LOW (off)

  row = 0                        'Start off at 0

'***** FUNCTIONS ******

RowScan1:
'RowScan1 is the first half of a routine to handle the appearance of all the LEDs lit up at once
  HIGH row                  'turn on row
    OUTH = col(row)         'turn on relevant columns all at once (target pins 8-15 by using OUTH)

      'Wait for data from Processing via the serial port
      'Give it a window of approx. 7ms, otherwise keep on row scanning with current data
      SERIN SerialPin, Baudmode, 7, RowScan2, [WAIT("A"), STR col\8]

      'If data was received, respond back to Processing with a "1"
      SEROUT SerialPin, Baudmode, ["1"]


RowScan2:
'RowScan2 is the second half of a routine to handle the appearance of all the LEDs lit up at once

    OUTH = 0                  'turn off all the columns
  LOW row                     'turn off row

  row = row + 1               'increment row, if we're at 8, we need to start back at 0
  IF (row = 8) THEN row = 0

GOTO RowScan1