Copy/Paste the code below into an empty arduino sketch. Then compile and upload it to your metro.
/* --------------------------------------------------------- * | Arduino Experimentation Kit Example Code | * | CIRC-05 .: 8 More LEDs :. (74HC595 Shift Register) | * --------------------------------------------------------- * * We have already controlled 8 LEDs however this does it in a slightly * different manner. Rather than using 8 pins we will use just three * and an additional chip. * * */ //Pin Definitions //Pin Definitions //The 74HC595 uses a serial communication //link which has three pins int data = 2; int clock = 3; int latch = 4; //Used for single LED manipulation int ledState = 0; const int ON = HIGH; const int OFF = LOW; /* * setup() - this function runs once when you turn your Arduino on * We set the three control pins to outputs */ void setup() { pinMode(data, OUTPUT); pinMode(clock, OUTPUT); pinMode(latch, OUTPUT); } /* * loop() - this function will start after setup finishes and then repeat * we set which LEDs we want on then call a routine which sends the states to the 74HC595 */ void loop() // run over and over again { int delayTime = 100; //the number of milliseconds to delay between LED updates for(int i = 0; i < 256; i++){ updateLEDs(i); delay(delayTime); } } /* * updateLEDs() - sends the LED states set in ledStates to the 74HC595 * sequence */ void updateLEDs(int value){ digitalWrite(latch, LOW); //Pulls the chips latch low shiftOut(data, clock, MSBFIRST, value); //Shifts out the 8 bits to the shift register digitalWrite(latch, HIGH); //Pulls the latch high displaying the data } /* * updateLEDsLong() - sends the LED states set in ledStates to the 74HC595 * sequence. Same as updateLEDs except the shifting out is done in software * so you can see what is happening. */ void updateLEDsLong(int value){ digitalWrite(latch, LOW); //Pulls the chips latch low for(int i = 0; i < 8; i++){ //Will repeat 8 times (once for each bit) int bit = value & B10000000; //We use a "bitmask" to select only the eighth //bit in our number (the one we are addressing this time through value = value << 1; //we move our number up one bit value so next time bit 7 will be //bit 8 and we will do our math on it if(bit == 128){digitalWrite(data, HIGH);} //if bit 8 is set then set our data pin high else{digitalWrite(data, LOW);} //if bit 8 is unset then set the data pin low digitalWrite(clock, HIGH); //the next three lines pulse the clock pin delay(1); digitalWrite(clock, LOW); } digitalWrite(latch, HIGH); //pulls the latch high shifting our data into being displayed } //These are used in the bitwise math that we use to change individual LEDs //For more details http://en.wikipedia.org/wiki/Bitwise_operation int bits[] = {B00000001, B00000010, B00000100, B00001000, B00010000, B00100000, B01000000, B10000000}; int masks[] = {B11111110, B11111101, B11111011, B11110111, B11101111, B11011111, B10111111, B01111111}; /* * changeLED(int led, int state) - changes an individual LED * LEDs are 0 to 7 and state is either 0 - OFF or 1 - ON */ void changeLED(int led, int state){ ledState = ledState & masks[led]; //clears ledState of the bit we are addressing if(state == ON){ledState = ledState | bits[led];} //if the bit is on we will add it to ledState updateLEDs(ledState); //send the new LED state to the shift register }
The Metro's Power LED goes out
The chip is inserted backwards. Turn off the power to your Metro, then rotate the chip such that the half-moon cutout on the chip faces the top of the breadboard.
Still not working?
Sorry to sound like a broken record, but make absolutely sure your wiring is correct. If you're unsure: pull everything out and start fresh.
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