Weird output from chained 74HC595 shift registers

Question

EDIT 4/2/18: The Arduino tutorial schematics have been corrected! See https://github.com/arduino/Arduino/issues/6433 for that issue.

I have a project where I am trying to load a 16-bit number onto an EEPROM using an Arduino hooked up to two 74HC595 Shift registers.

I'm loosely following this Arduino tutorial: https://www.arduino.cc/en/Tutorial/ShiftOut, but I'm getting unexpected outputs depending on the number I try to load into the register. I've reduced everything to as simple a setup as I can, and have spent several hours trying to figure out what the heck is going wrong... obviously to no avail.

Here is the schematic - with the exception that I moved the capacitor off of ST_CP (why would they put that in the tutorial?) to between power and ground:

Here is my code:

#define SHIFT_DATA 2
#define SHIFT_CLK 3
#define SHIFT_LATCH 4

void setup() {
  pinMode(SHIFT_DATA, OUTPUT);
  pinMode(SHIFT_CLK, OUTPUT);
  pinMode(SHIFT_LATCH, OUTPUT);

  int address = 0b1111111111111111;  // Case 1
//int address = 0b0000000000000000;  // Case 2
//int address = 0b0101010101010101;  // Case 3
//int address = 0b1010101010101010;  // Case 4
//int address = 0b0101100110101110;  // Case 5

  shiftOut(SHIFT_DATA, SHIFT_CLK, MSBFIRST, (address >> 8)); // Load first 8 bits
  shiftOut(SHIFT_DATA, SHIFT_CLK, MSBFIRST, address);        // Load second 8 bits

  digitalWrite(SHIFT_LATCH, LOW);
  digitalWrite(SHIFT_LATCH, HIGH);
  digitalWrite(SHIFT_LATCH, LOW);
}

void loop() {
  // none
}

Here is a picture of my breadboard setup with Case 1 loaded:

And here follows my test cases.

1. All 1's (1111111111111111). Looks good.
2. All 0's (0000000000000000). Looks good.
3. Repeated 01's (0101010101010101). Looks good.
4. Repeated 10's (1010101010101010). Output: 1010101000000000. First 8 bits match, last 8 are zeros. Huh?
5. Random sequence (0101100110101110). Output: all over the place. Initially the first 8 bits match as in Case 4, but on repeated resets of the Arduino the output changes, with some weird momentary flickering going on for some of the LEDs. If I press it enough times I can get it back to the initial output, but never what I expect. I am completely stumped. Here is an animated gif of this behavior running on the breadboard: http://i.imgur.com/KEwpSXe.gifv.

What could my problem be? I assume it's something very simple and I'm being an idiot.

Answer 1

You should change your capacitors.

You only have 0.1µF instead of 1µF for the bulk capacitor (which really wants to be 10µF). In addition you should add 0.1µF (100nF) capacitors directly across the power pins of each chip:

Answer 2

I have forum post about the 595 chip and a question and answer about SPI.

You can use SPI to do the transfer. This is faster and simpler than shiftOut. Also you need to bring the latch low before transferring the data.

Simple example sketch:

#include <SPI.h>

const byte LATCH = 10;

void setup ()
{
  SPI.begin ();
}  // end of setup

byte c;
void loop ()
{
  c++;
  digitalWrite (LATCH, LOW);
  SPI.transfer (c);
  digitalWrite (LATCH, HIGH);
  delay (20);
}  // end of loop