This information was partially found at http://gathering.tweakers.net/forum/list_message/29939964#29939964

more discussion on http://www.circuitsonline.net/forum/view/60243/1/dot+matrix+baco

J1: data input

J2: data output (for connecting a second board → this will effectually make one large shift register per row. Connecting two boards yields horizontal shift registers of 64 bits.

Bovenste helft en onderste helft hebben aparte data ingangen (LDAT en UDAT)

while(1) {
 for y=0 to 8 {
  for x=0 to 32 {
   maak LDAT hoog als je op (x,y+8) een pixel wilt weergeven
   maak UDAT hoog als je op (x,y) een pixel wilt weergeven
   maak CLK laag
   maak CLK hoog
  }
  maak OE hoog (dit zet alle LEDs tijdelijk uit)
  maak STROBE laag
  maak STROBE hoog
  zet [A2..0] naar y
  maak OE laag
  wacht een tijd, afhankelijk van de gewenste refreshrate
 }
}

Is working!

The code is written for WinAVR. Also the AVRlib.zip libraries by Pascal Stang have been used. You can download them from here

//*****************************************************************************
// File Name	: main.c
// 
// Titel		: Display controller
// Revisie		: 1.0
//
// Revision History:
// When			Who			Description of change
// -----------	-----------	-----------------------
// 05-Mrt-2007  e13		generic Mublock Source
// 29-Dec-2008  e13             adapted for display
//*****************************************************************************


//----- Include Files ---------------------------------------------------------
#include <avr/io.h>		// include I/O definitions (port names, pin names, etc)
#include <avr/interrupt.h>	// include interrupt support

#include "global.h"		// include our global settings
#include "uart.h"		// include uart function library
#include "rprintf.h"	// include printf function library
#include "a2d.h"		// include A/D converter function library
#include "timer.h"		// include timer function library (timing, PWM, etc)
#include "vt100.h"		// include VT100 terminal library
#include "pic.h"

#define limit(number,boundary) ( ((number)>(boundary))?(boundary):( ((number)<(-boundary))?(-boundary):(number)) )

#define GRAYINC (1<<3)

#define CLK PC7
#define A0 PC4
#define A1 PC5
#define A2 PC6
#define UDAT PB1
#define LDAT PB0
#define STROBE PB3
#define OE PB2

unsigned char dispmem[512];

void Timer0Overflow(void);
volatile int fastcount;
volatile char hzflag;

void flashGreen(void);
void flashRed(void);

int main(void)				// hoofdprogramma
{
	int x,y,n;
	outb(DDRB,0x0F);
	outb(PORTB,0x0F);
	outb(PORTA,0xF0); //pullup on 1 and 2
	outb(DDRA,0x00);
	outb(DDRC,0xF0);
	outb(PORTC,0xF0);
	// initialize our libraries
	// initialize the UART (serial port)
	uartInit();
	// set the baud rate of the UART for our debug/reporting output
	uartSetBaudRate(9600);
	// set uartSendByte as the output for all rprintf statements
	rprintfInit(uartSendByte);
	// initialize the timer system
	timerInit();
	// initialize vt100 library
	vt100Init();
	// initialize cmdline system
	// turn on and initialize A/D converter
	a2dInit();
	// set the a2d prescaler (clock division ratio)
	// - a lower prescale setting will make the a2d converter go faster
	// - a higher setting will make it go slower but the measurements
	//   will be more accurate
	// - other allowed prescale values can be found in a2d.h
	a2dSetPrescaler(ADC_PRESCALE_DIV32);
	// set the a2d reference
	// - the reference is the voltage against which a2d measurements are made
	// - other allowed reference values can be found in a2d.h
	a2dSetReference(ADC_REFERENCE_AVCC);
	// use a2dConvert8bit(channel#) to get an 8bit a2d reading
	// use a2dConvert10bit(channel#) to get a 10bit a2d reading
	timer0SetPrescaler(TIMER_CLK_DIV8);	
	TCNT0=0x83; //16000Hz @ 8 - 16MHz
	timerAttach(TIMER0OVERFLOW_INT, Timer0Overflow);
	
	for (x=0; x<512; x++) dispmem[x]=picture[x];
	
	
	sei();
	
	while(1)
	{

	}
	return 0;
}


void Timer0Overflow(void)
{
	static char rowno; //number of the row we're at now
    static short pos; //position in display memory
    static unsigned char comp; //compare-value for grayscales
    char x;
	TCNT0=0x83;	//16000 hz
    //Send next line    
    PORTB&=~(1<<STROBE); //disable strobe in advance
    for (x=0; x<32; x++) 
	{ //for each pixel:
		PORTB&=~((1<<UDAT)|(1<<LDAT)); //clear data inputs
		PORTC&=~(1<<CLK); //reset clock in advance
		if (dispmem[pos]>comp) PORTB|=(1<<UDAT); //if pixel should be shown, set output
		if (dispmem[pos+(32*8)]>comp) PORTB|=(1<<LDAT); //same for the lower 8 rows
		pos++; //next memory position
		PORTC|=(1<<CLK); //clock in the bits
		comp+=128; //invert phase of pwm every pixel
	}
    comp+=128; //invert phase of pwm every row too
    PORTB|=(1<<STROBE); //latch in the led values


    PORTB|=(1<<OE); //disable led output
    //select correct row
    PORTC&=~((1<<A0)|(1<<A1)|(1<<A2));
    if (rowno&1) PORTC|=(1<<A0);
    if (rowno&2) PORTC|=(1<<A1);
    if (rowno&4) PORTC|=(1<<A2);
    PORTB&=~(1<<OE); //enable led output
    rowno++; //Ok, this row is done.
    if (rowno>7) 
	{ //Frame done?
		rowno=0; //reset row count
		pos=0; //reset memory pos
		comp+=128+GRAYINC; //invert phase of pwm and increase
    }
}

void flashRed(void){ if (PORTB & 0x01) cbi(PORTB,0); else sbi(PORTB,0);}
void flashGreen(void){ if (PORTB & 0x02) cbi(PORTB,1); else sbi(PORTB,1);}

And ofcourse the image file:

//pic.h 
//Size: 32 16
const char picture[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,25,0,25,0,0,25,0,0,25,25,0,0,25,25,0,0,25,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,25,0,25,0,25,0,25,0,25,0,25,0,25,0,25,0,25,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,25,25,25,0,25,25,25,0,25,25,0,0,25,25,0,0,25,25,25,0,0,0,0,0,0,0,0,0,0,0,0,0,25,0,25,0,25,0,25,0,25,0,0,0,25,0,0,0,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,0,25,0,25,0,25,0,25,0,25,0,0,0,25,0,0,0,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,25,25,25,0,25,25,25,0,25,0,0,0,25,0,0,25,0,25,0,25,25,25,0,0,25,0,0,25,25,0,0,0,25,0,25,0,25,0,0,0,25,0,0,0,25,0,0,25,0,25,0,25,0,0,0,25,0,25,0,25,0,25,0,0,25,0,25,0,25,25,0,0,25,0,0,0,25,0,0,25,25,25,0,25,25,0,0,25,25,25,0,25,25,0,0,0,25,0,25,0,25,0,0,0,25,0,25,0,25,0,0,0,25,0,0,25,0,0,0,25,0,25,0,25,0,25,0,0,25,0,25,0,25,25,25,0,0,25,0,25,0,0,0,0,25,0,0,25,25,25,0,25,0,25,0,25,0,25,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

Generated with the following Processing file:

/**
 * Pixel Print
 *
 * Print brightness values for pixels 
 */
 
PImage a;
int[] aPixels;
int direction = 1;
boolean onetime = true;
float signal;

void setup() 
{
  size(32, 16);
  aPixels = new int[width*height];
  a = loadImage("test.bmp");
  for(int i=0; i<width*height; i++) {
    aPixels[i] = a.pixels[i];
    print((int)brightness(aPixels[i])/10);
    print(',');
  }
}

void draw() 
{
}