Led with shift register 74hc595 doesn't work by SPI

[kentforth]

Hello Pieter!

My board is Arduino Leonardo

I connected a led to shift register SN74HC595N by SPI. It doesn't work. Led blinks fast even if I change a code. It seems it work incorrectly. But if I connect a led in a regular way(digital pins instead of iscp header pins) with a sketch for regular connection it works fine

Did I make wrong wiring?

Here is i connected all the stuff:

Here is my sketch:

`#include // Include the Control Surface library.

using namespace ExtIO; // Bring the ExtIO pin functions into your sketch

// Instantiate a shift register with the SPI slave select pin as latch pin, most // significant bit first, and a total of 8 outputs. SPIShiftRegisterOut<8> sreg = {10, MSBFIRST};

const pin_t ledPin = sreg.pin(1); // first pin of the shift register

void setup() { sreg.begin(); // Initialize the shift registers pinMode(ledPin, OUTPUT); // You don't even need this line, since // shift registers are always outputs }

void loop() { // Toggle the state of the LED every 1/2 second digitalWrite(ledPin, HIGH); delay(700); digitalWrite(ledPin, LOW); delay(700); }`

[tttapa]

Master Reset and Output Enable are floating, and the bypass capacitor is missing. See this page: https://www.arduino.cc/en/tutorial/ShiftOut

[kentforth]

It is strange that author of this article made two different pinouts for a one shift register pinouts are different.

I don't understand what pinout is the correct one. Can you show me the picture how you connected leds by SPI with shift register when you tested leds?

[tttapa]

The second one is not a pinout, it's just the schematic, the pins have been rearranged to make routing of the wires easier. The first one is the actual pinout.

[kentforth]

Here is how I connected Arduino Leonardo to shift register by SPI. It works! Thank you Pieter!

[tttapa]

I just noticed that the breadboard view on the Arduino page is wrong. The bypass capacitor should be between Vcc and ground, as close to the chip as possible. The breadboard (and your diagram above) shows it between ST_CP and ground, which is completely wrong.

[kentforth]

I checked your suggestion, it works

[kentforth]

What if I want to connect leds to another shifter register. Can you show me a simple sketch with one led on one shift register and one led on the second shift register?

[tttapa]

#include <Control_Surface.h> // Include the Control Surface library.

using namespace ExtIO; // Bring the ExtIO pin functions into your sketch

// Instantiate a chain of shift registers with the SPI slave select pin as 
// latch pin, most significant bit first, and a total of 16 outputs.
SPIShiftRegisterOut<16> sreg = {SS, MSBFIRST};

const pin_t ledPinA = sreg.pin(0); // first pin of the first shift register
const pin_t ledPinB = sreg.pin(8); // first pin of the second shift register

void setup() {
  sreg.begin();             // Initialize the shift registers
  pinMode(ledPinA, OUTPUT); // You don't even need these lines, since
  pinMode(ledPinB, OUTPUT); // shift registers are always outputs
}

void loop() {
  // Toggle the state of the LEDs every 1/2 second
  digitalWrite(ledPinA, HIGH);
  digitalWrite(ledPinB, LOW);
  delay(500);
  digitalWrite(ledPinA, LOW);
  digitalWrite(ledPinB, HIGH);
  delay(500);
}

Change the latch pin from SS to pin 10 if you're using a Leonardo.

[kentforth]

Thank you! I appreciate your work!