help me improve my code for controlling 64 leds with 2 74HC595N ic's

Other Hardware LEDs and Multiplexing
21

aimmet:
Daisy chain all 3 pins? How would the the Arduino know which 595 is grounded then?

OK, "daisy chaining" means that you feed the output (pin 9) of the first shift register into the input of the second. Both have the same clock and latch connection.

You now have a 16 bit shift register. You load it with two successive shiftOut operations, the first one puts the data into the first register then the second shiftOut moves that same data into the second register as it loads the new data into the first. Only after both shiftOut operations, do you strobe the latch(es - together).

We can help you with the code to do that, if you show how you have actually wired it. :grinning:

22

Paul__B:
OK, "daisy chaining" means that you feed the output (pin 9) of the first shift register into the input of the second. Both have the same clock and latch connection.

You now have a 16 bit shift register. You load it with two successive shiftOut operations, the first one puts the data into the first register then the second shiftOut moves that same data into the second register as it loads the new data into the first. Only after both shiftOut operations, do you strobe the latch(es - together).

We can help you with the code to do that, if you show how you have actually wired it. :grinning:

This is how it looks like right now with out daisy chaining, just keep in mind there not all red leds its actually Red, green, blue, white, Red, green, blue, white, repeated 8 times going down. and i could not find a capacitor unfortunately
Picture of set up

23

frankvnz:
Just a general comment on coding style: If you're representing bit patterns, do NOT write the equivalent number in decimal. Write in hex or binary (or octal, if you must). The issues with 132, 253, 147 etc that were mentioned earlier would have been more immediately apparent.

Looking at your circuit, I guess the idea is to output 0V to the negative side of an LED and 5V to the positive side; the LED will illuminate. An RGBW LED is actually 4 LEDs in one package, so you actually have 256 LEDs to control, hence you need to use all 8 bits of both shift registers. It would be helpful to know exactly what the logical arrangement of the LEDs vs shift registers is. Do you see it as 4 rows of 16 LEDs, with 4 outputs to select the colour? Or an 8x8 grid of LEDs, with a 2x2 combination to select the colour?

But, generally speaking, if you output 0x01 to the positive side of the LED matrix and 0xFE to the negative side, you should illuminate one colour of the LED at the bottom left corner of your matrix.

Beware that turning on more than one LED in a row or column may exceed the current capabilities of a shift register (35mA) and possibly destroy it. Probably you should have 8 transistors controlled by each shift register to deliver the current to the LEDs. But then you somehow need to limit the current flowing through each LED.

So, for the positive side, values you should use are one of: 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80.
For the negative side, you want one of the inverses of those: 0xFE, 0xFD, 0xFB, 0xF7, 0xEF, 0xDF, 0xBF, 0x7F.

To cycle through bits, the << operator is useful. e.g. the following (untested code!) will cycle through all your LEDs.

for (int x = 1; x < 0x100; x <<= 1) {

digitalWrite(latchPin, LOW);
 //Send x to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 1st 74595
 shiftOut(dataPin, clockPin, MSBFIRST, x);  // shifting out the bits:
 digitalWrite(latchPin, HIGH);

for (int y = 1; y < 0x100; y <<= 1) {
   digitalWrite(latchPin2, LOW);
   //Send inverse of y to Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 of 2nd 74595
   shiftOut(dataPin2, clockPin2, MSBFIRST, ~y);  // shifting out the bits NB: inverse Y
   digitalWrite(latchPin2, HIGH);
   delay(1000);
 }
}

I just used a 8 x 8 pre built matrix and your code works! Cycling through each led it cycles through all the leds but for the first 3 seconds its blank but then the top left led lights up and it starts doing down the column then goes to the next row. So can you give a little better explanation on how this works exactly? How do i match the positive and negative side to get a LED that I want? Say I want the LED from the 3rd colmn and 2nd row to light up?