SPI Data Transfer to 74HC595 [closed]

Question

I want to send data to my 74HC595 via SPI (in Arduino). But I could not manage to blink my LEDs. My code is in below.

#include <SPI.h>

int clock_pin = 13; // SCLK
int data_pin = 11;  // MOSI
int latch_pin = 10; // SS

uint8_t led ;
void setup() {
  pinMode(latch_pin, OUTPUT); // enable pin 10 as latch pin
  
  // SPI Setup
  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV8); 
  SPI.setBitOrder(LSBFIRST);  
  digitalWrite(latch_pin, HIGH);
}

void loop() {
  led = 0b10101111;
  put_Register(led);
  delay(500);  
  led = 0b10101101;
  put_Register(led);
  delay(5000);                  
}

void put_Register(byte led) {
  digitalWrite(latch_pin, LOW);
  SPI.transfer(led);       
  digitalWrite(latch_pin, HIGH);
}

Answer 1

Your latch signal timing is wrong. Is is low during a serial transfer and needs a short positive pulse to transfer the shift register content to the output register.

Do not forget to set the output enable pin /OE to low and master reset /MR to high.

void setup() {
  //.... 
  pinMode(latch_pin, OUTPUT);
  digitalWrite(latch_pin, LOW);  // initial low
}


void put_Register(byte led) {
  SPI.transfer(led);       
  digitalWrite(latch_pin, HIGH);  // short high pulse on STCP
  digitalWrite(latch_pin, LOW);
}