watch futurama on an 8x8 pixel screen

Step 7 Draw a frame

the data is stored in arrays of unsigned chars, which are 8 bit numbers. PROGMEM forces the data to be stored in program memory, rather than allowing the avr to copy all of the data to ram. the purpose here is to reduce the number of steps involved and to maximize the amount of info that can be stored and quickly retrieved.

unsigned char green_vals[][8] PROGMEM = { { 0x01, 0xff, 0x80, 0xff, etc...unsigned char red_vals[][8] PROGMEM = { { 0x01, 0x02, 0x03, 0x04, etc...

remember that the matrix is only 8 leds across, meaning that each entry in those arrays corresponds to a complete description of an entire row. so looping through 8 of them in succession is a frame...

for (i=0; i<8; i++){  set_frame( red_vals[ 0 ][ i ], green_vals[ 0 ][ i ], (1<<i) );  show_frame( TIME_TO_SHOW_LINE );}

except that won't work, because of PROGMEM up there... just call pgm_read_byte() on red_vals and green_vals to fix it.

set_frame( pgm_read_byte( &red_vals[ 0 ][ i ] ), pgm_read_byte( &green_vals[ 0 ][ i ] ), (1<<i) );

the set_frame() function is pretty simple:

/* send frame line data to shift registers and set appropriate grounder pin */void set_frame ( unsigned char red, unsigned char green, unsigned char gnd ){	/* just a loop variable */	unsigned char i = 0;		/* set up red, loop through all 8 bits */	for (i=0; i<8; i++)	{		if ( red & (1<<i) ) PORTB |= red_ser;	// if it's a one then serial pin hi		else PORTB &= ~red_ser;			// otherwise make sure it's low		if ( green & (1<<i) )  PORTB |= green_ser;   // if it's a one then pin hi		else  PORTB &= ~green_ser; 	// otherwise make sure it's low		PORTB |= ser_sck;	// clock up		PORTB &= ~ser_sck;	// clock down         }        PORTB &= ~red_ser;		// be sure to leave red's ser line low	PORTB &= ~green_ser;		// leave green serial pin low	/* set the grounder pin for this frame line to low */	PORTD = ~gnd;		// upsidedown logic... }