Controlling 16 LED's with two 74HC595 Shift register

[CanadaForces]

Hello,

I am trying to controll 16 LED's light using TWO 74HC595 shift registers. (see schematic in attachment).
I am trying to run a simple program in a loop that would turn all the light OFF at the same time and then turn them back on (still in unisome).

Now, when I run my program, this is the result I am getting:

The first 8 light would go off.
The next 8 would go off.
Then the first 8 light would go ON,
The next 8 lights would go ON.
And son on ....

Can anyone please tell me what I am doing wrong.

int clockPin = 11;
int latchPin = 8;
int dataPin =12;

byte LED1 = 0b1111111111111111;
byte LED2 = 0b0000000000000000;

void setup (){

  pinMode (clockPin, OUTPUT);
  pinMode (latchPin, OUTPUT);
  pinMode (dataPin, OUTPUT);
}


void loop (){

  digitalWrite (latchPin, LOW);
  shiftOut (dataPin, clockPin, MSBFIRST, LED1);
  digitalWrite (latchPin, HIGH);

  delay (1000);

  digitalWrite (latchPin, LOW);
  shiftOut (dataPin, clockPin, MSBFIRST, LED2);
  digitalWrite (latchPin, HIGH);

  delay (1000);
  
}

[guix]

Hello,

A byte is 8 bits

[guix]

Explaination of what your code is doing :

Send 11111111 to the first 595
Delay
Send 00000000 to the first 595, so the second 595 will be 11111111 (as all 8 bits of the first 595 were shifted into the second)
Delay
Send 11111111 to the first 595, so the second 595 will be 00000000 (as all 8 bits of the first 595 were shifted into the second)
etc...

Solution :

You have to change the data type to a 16 bits type (uint16_t), and call shiftOut twice, each with half the bits of your 16 bits of data

uint16_t LED1 = 0b1111111111111111;
...
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 8);
shiftOut(dataPin, clockPin, MSBFIRST, LED1);

[PieterP]

The compiler should have warned you about this. If it didn't, go to your Arduino IDE preferences right now and enable all warnings.

warning: large integer implicitly truncated to unsigned type [-Woverflow]
 byte LED1 = 0b1111111111111111;
             ^~~~~~~~~~~~~~~~~~

Pieter

[CanadaForces]

PieterP:
The compiler should have warned you about this. If it didn't, go to your Arduino IDE preferences right now and enable all warnings.

warning: large integer implicitly truncated to unsigned type [-Woverflow]

byte LED1 = 0b1111111111111111;
            ^~~~~~~~~~~~~~~~~~

Pieter

Hello Pieter,

Actually, I got that warning.
But after changing the code, I am getting this error:

exit status 1
'unit16_t' does not name a type

[guix]

Not unit16_t but uint16_t, as in unsigned integer of 16 bits

You may want to try this little library: GitHub - bildr-org/Shift-Register-8-Bit-74HC595: Arduino code to control the 74HC595 8-bit Shift-Register

[CanadaForces]

guix:
Not unit16_t but uint16_t, as in unsigned integer of 16 bits

You may want to try this little library: GitHub - bildr-org/Shift-Register-8-Bit-74HC595: Arduino code to control the 74HC595 8-bit Shift-Register

You are the best.
Thank you so much

[CanadaForces]

guix:
Explaination of what your code is doing :

Send 11111111 to the first 595
Delay
Send 00000000 to the first 595, so the second 595 will be 11111111 (as all 8 bits of the first 595 were shifted into the second)
Delay
Send 11111111 to the first 595, so the second 595 will be 00000000 (as all 8 bits of the first 595 were shifted into the second)
etc...

Solution :

You have to change the data type to a 16 bits type (uint16_t), and call shiftOut twice, each with half the bits of your 16 bits of data

uint16_t LED1 = 0b1111111111111111;

...
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 8);
shiftOut(dataPin, clockPin, MSBFIRST, LED1);

Hello Quix
If I added a third 74HC595 to control an additional 8 LEDs to make it 24 LEDs in total, can I modify the code as below:

uint32_t LED1 = 0b1111111111111111;
...
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 8);
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 8);
shiftOut(dataPin, clockPin, MSBFIRST, LED1);

[anon73444976]

Check the lengths of your right shifts.

[guix]

As AWOL said (but you probably didn't understand), you have to right shift ( >> ) the correct amount of bits

//                XWVUTSRQPONMLKJIHGFEDCBA
uint32_t LED1 = 0b111111111111111111111111;
...
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 16); // send bits X-Q
shiftOut(dataPin, clockPin, MSBFIRST, LED1 >> 8);  // send bits P-I
shiftOut(dataPin, clockPin, MSBFIRST, LED1);       // send bits H-A

[CrossRoads]

Add 0.1uF caps from the '595 VCC pins to Gnd.
I don't see pin 9 from one chip going to 14 on the other, that is needed to pass the data from device to device.