Here is one I found using google "Arduino MM5450". It uses software SPI rather then the AVR's built in SPI hardware, but it might be useful to pick apart as it seems to be very well commented.
// Program..: stairway_v.1_code.pde
// Author...: l.e. hughes
// Date.....: 27 May 2011
// Notes....: Basic, simple example of using shift registers to control the MM5450/5451
// LED driver. This program was specifically written for the 5450, but should
// also work with the 5451 and be easily modified for others. The 5450/5451
// is latching and requires 36 signal databits to send all of the information
// to control the LEDs (34 for the 5450; 35 for the 5451). There are minor
// differences in the chip between the manufacturers, please read the appropriate
// datasheet(s) before connecting power.
//
#define BITSB 8 // number of bits per byte, used for code clarity
#define DATABITS 36 // what we must send to the chip in order to control the lights
#define STARTBIT 1 // value of the starting bit;
const int clockPin = 3; // connect Arduino pin 3 to clock pin (21) on the 5450
const int dataPin = 6; // connect Arduino pin 6 to data pin (22) on the 5450
const int delayTime = 200; // delay between lights
// The following line just computes the number of bytes we will need in the ledArray to hold all of
// bits of data for the signal; it could be declared statically.
//
const int arrayLen = (int)((DATABITS-1)/BITSB) + 1;
// This is the actual array that will hold the signal bits. This program, for the 5450/5451, will
// need 5 bytes for a total of 40 bits.
//
byte ledArray[arrayLen]; // for this chip, length is 5 and that could hold 40 values
typedef enum { // this exists primarily for code clarity
OFF, ON
} ledState;
// Start program -------------------------------------------------------------------------------------
//
void setup() {
pinMode(clockPin, OUTPUT); // we don't need a latch pin since the 5450/5451 latched after
pinMode(dataPin, OUTPUT); // receiving the 36 databits
allOff(); // start with all lights off
}
void loop() {
allOn(); // turn all lights on
sendDatabits();
delay(delayTime);
allOff(); // turn all lights off
sendDatabits();
delay(delayTime);
for(int i = 1; i < DATABITS; i++) { // turn all lights on, in numerical order, starting with light 1
setLight(i,ON);
sendDatabits();
delay(delayTime);
}
for(int i = (DATABITS-1); i > 0; i--) {
setLight(i,OFF); // turn all lights off, in reverse numerical order, starting
sendDatabits(); // with the last light
delay(delayTime);
}
for(int i = (DATABITS-1); i > 0; i--) {
setLight(i,ON); // turn all lights on, in reverse numerical order, starting
sendDatabits(); // with the last light
delay(delayTime);
}
for(int i = 1; i < DATABITS; i++) { // turn all lights off, in numerical order, starting with light 1
setLight(i,OFF);
sendDatabits();
delay(delayTime);
}
for(int i = 0; i < 3; i++) { // flash the lights 3 times
allOn();
sendDatabits();
allOff();
sendDatabits();
delay(100);
}
delay(5000); // wait 5 seconds before starting loop over
// Other examples:
//
// setLight(1,ON); // This would turn light 1 on
// sendDatabits();
// toggleLight(1); // This would turn it off
// sendDatabits();
// setLight(2,ON); // Turn on lights 2 and 4
// setLight(4,ON);
// sendDatabits();
}
// Subroutine that sends all of the DATABITS to the chip. It begins by first sending the startbit, then it
// uses the Arduino shiftOut function to send the bits in each byte of the ledArray. I could have put the
// STARTBIT into the ledArray but decided that I liked it better outside of the array. Any time you want
// to turn lights on or off, this routine must be called after setting the appropriate bits in the ledArray.
//
void sendDatabits() {
digitalWrite(clockPin, LOW);
delay(2);
digitalWrite(dataPin, STARTBIT);
delay(2);
digitalWrite(clockPin, HIGH);
delay(5);
digitalWrite(clockPin, LOW);
delay(2);
for(int i = 0; i < arrayLen; i++) {
shiftOut(dataPin, clockPin, LSBFIRST, ledArray[i]);
}
}
// Subroutine that takes a light (output pin) as a sole argument and sets the bit value for that pin
// to the opposite of its current setting (toggle).
//
void toggleLight(int pin) {
byte arrayElem = int((pin-1)/BITSB); // which element of the ledArray is pin in
byte byteElem = (pin - (arrayElem * BITSB)) - 1; // and which bit in that byte is the pin
ledArray[arrayElem] ^= (1 << byteElem); // toggle byteElem
}
// Subroutine that takes a light (output pin) and an additional argument and sets the bit value
// for that pin appropriately
//
void setLight(int pin, byte val) {
byte arrayElem = int((pin-1)/BITSB); // which element of the ledArray is pin in
byte byteElem = (pin - (arrayElem * BITSB)) - 1; // and which bit in that byte is the pin
ledArray[arrayElem] |= (val << byteElem); // zero vals require a two-step process,
if(val == 0) { // first we set them to a one and then
ledArray[arrayElem] ^= (1 << byteElem); // toggle them
}
}
// Subroutine that turns all lights on. Because the STARTBIT is 1 or ON, we don't want to set any
// bits above 35 to ON, lest it be interpreted as the start of another set of databits. Better error
// checking would be to make sure that no bit > 35 was ever set to 1.
//
void allOn() {
for(int i = 1; i < DATABITS; i++) {
setLight(i, ON);
}
}
// Subroutine that turns all lights off
//
void allOff() {
for(int i = 0; i < arrayLen; i++) {
ledArray[i] = 0;
}
}
