SD Card and 74HC595

In my previous blog, I explained usage of Shift register using Node MCU and shown how to extend the additional digital input and output pins using 74HC595 and CD4021B shift register. In this blog we will use 74HC595 along with SD card and Node MCU.

74HC595: This is serial to parallel shift out register. You can use 8 digital output.This works in synchronous serial communication.

SD Card: SD Card will be used to store the data.

SD Card and 74HC595 Schematic

PIN Connections:

SD Card	Node MCU	74HC595N
MISO	D6 (GPIO12)
SCK	D5 (GPIO14)	SCK/SRCLK/SH_CP (PIN: 11) CLOCK PIN
	D3 (GPIO0)	RCK/SH_CP/RCKL (PIN: 12) LATCH
MOSI	D7 (GPIO13)	SER/DS (PIN: 14) DATA
CS/SS	D8 (GPIO15)
GND	GND	G/OE
	VCC (3.3V)	SCL/MR/SRCLR
VCC	VU (5V)

Once connection is made, you can use Arduino IDE to program the device. First thing is to initialise the Output pins as below,

pinMode(LATCHOUT_PIN, OUTPUT);

pinMode(CLOCK_PIN, OUTPUT);

SD Card Initialisation can be done as below,

pinMode(CHIPSELECT_PIN, OUTPUT);

// see if the card is present and can be initialized:

if (!SD.begin(CHIPSELECT_PIN)) {

// don't do anything more:

Serial.println("Card failed, or not present");

return false;

} else {

if (!isBaseDirAvailable()) {

createDirectory();

}

return true;

}

Serial.println("card initialized.");

Once initialisation is complete, then call the write and read method of the SD card to read or write on SD card device. Also in parallel you can set the digital output pin as per requirement.

Reading the file:

File readFile = SD.open(ROOT_DIRECTORY);

readFile.rewindDirectory();

dataReader(readFile, 0);

readFile.flush();

readFile.close();

Here if you are reading the files in loop then make sure that you rewind directory.

Writing the file:

if (!checkSpace(MINIMUM_SDCARD_SIZE)) {

deleteFile();

}

//SdFile::dateTimeCallback(TimeRecorder::dateTime);

File dataFile = SD.open(filename, FILE_WRITE);

uint32_t fileSize = dataFile.size();

fileSize /= 1024;

// if the file is available, write to it:

if (dataFile) {

dataFile.println(output);

// print to the serial port too:

//Serial.println(output);

} else {

Serial.println("Error in reading/opening file " + filename);

//dataFile.clearWriteError();

//Serial.print("Write Error: ");

}

dataFile.flush();

dataFile.close();

In above code before writting multiple files, we are checking the space. Also, if you are using Real Time Clock then you may want current timestamp while writting the file. This can be acheived as below,

SdFile::dateTimeCallback(TimeRecorder::dateTime); //TimeRecorder is your RTC setup class

dateTime callback method can be as below,

static void dateTime(uint16_t* date, uint16_t* time) {

static RTC_DS1307 RTCCall;

DateTime now = RTCCall.now();

// return date using FAT_DATE macro to format fields

*date = FAT_DATE(now.year(), now.month(), now.day());

// return time using FAT_TIME macro to format fields

*time = FAT_TIME(now.hour(), now.minute(), now.second());

}

Please find complete program as below,

	#include "Arduino.h"
	#include <SPI.h>
	#include <SD.h>
	#define CHIPSELECT_PIN 15
	#define MINIMUM_SDCARD_SIZE 100
	//Pin connected to ST_CP of 74HC595
	//D3
	#define LATCHOUT_PIN 0
	//Pin connected to SH_CP of 74HC595
	//D5
	#define CLOCK_PIN 14
	////Pin connected to DS of 74HC595
	//D7
	#define DATAOUT_PIN 13
	byte dataOut = 0xFF;
	int fileCounter = 0;
	String ROOT_DIRECTORY = "/gtlog";
	boolean baseDir = false;
	void setup() {
	Serial.begin(115200);
	cardInitialization();
	initializeDigitalPIN();
	}
	// The loop function is called in an endless loop
	void loop() {
	String filename = getNextFileName();
	writeFile(filename, "Test String");
	delay(2000);
	readFileFromRoot();
	delay(2000);
	setDigitalPINOut(dataOut);
	}
	String getNextFileName() {
	//String filename = String("log") + (fileCounter++) + String(".txt");
	String filename = ROOT_DIRECTORY + "/" + (fileCounter++) + String(".txt");
	Serial.print("Filename is ");
	Serial.println(filename);
	return filename;
	}
	boolean cardInitialization() {
	pinMode(CHIPSELECT_PIN, OUTPUT);
	// see if the card is present and can be initialized:
	if (!SD.begin(CHIPSELECT_PIN)) {
	// don't do anything more:
	Serial.println("Card failed, or not present");
	return false;
	} else {
	if (!isBaseDirAvailable()) {
	createDirectory();
	}
	return true;
	}
	Serial.println("card initialized.");
	}
	void readFileFromRoot() {
	File readFile = SD.open(ROOT_DIRECTORY);
	readFile.rewindDirectory();
	dataReader(readFile, 0);
	readFile.flush();
	readFile.close();
	}
	void dataReader(File root, int numTabs) {
	Serial.println("*****Reading file*****");
	while (true) {
	File entry = root.openNextFile();
	if (!entry) {
	Serial.println("No more files");
	// no more files
	break;
	}
	for (uint8_t i = 0; i < numTabs; i++) {
	Serial.print('\t');
	}
	Serial.println(entry.name());
	if (entry.isDirectory()) {
	Serial.println("/");
	dataReader(entry, numTabs + 1);
	} else {
	// files have sizes, directories do not
	Serial.print("\t\t");
	String fileName = entry.name();
	Serial.print(fileName);
	String line;
	while (entry.available()) {
	line = entry.readStringUntil('\n');
	}
	if (SD.exists(fileName)) {
	Serial.println("Deleting the file " + fileName);
	SD.remove(fileName);
	Serial.print("File deleted");
	}
	//Serial.println(entry.size(), DEC);
	//Serial.println(line);
	}
	entry.close();
	}
	}
	void writeFile(String filename, String output) {
	Serial.print("CustomSDCard::writeFile: ");
	Serial.println(filename);
	if (!checkSpace(MINIMUM_SDCARD_SIZE)) {
	deleteFile();
	}
	//SdFile::dateTimeCallback(TimeRecorder::dateTime);
	File dataFile = SD.open(filename, FILE_WRITE);
	uint32_t fileSize = dataFile.size();
	fileSize /= 1024;
	// if the file is available, write to it:
	if (dataFile) {
	dataFile.println(output);
	// print to the serial port too:
	//Serial.println(output);
	} else {
	Serial.println("Error in reading/opening file " + filename);
	//dataFile.clearWriteError();
	//Serial.print("Write Error: ");
	}
	dataFile.flush();
	dataFile.close();
	}
	boolean isBaseDirAvailable() {
	return baseDir;
	}
	void deleteFile() {
	File deleteFile = SD.open(ROOT_DIRECTORY);
	deleteFile.rewindDirectory();
	deleteEachFile(deleteFile, 0);
	deleteFile.flush();
	deleteFile.close();
	}
	void createDirectory() {
	if (!SD.exists(ROOT_DIRECTORY)) {
	SD.mkdir(ROOT_DIRECTORY);
	}
	baseDir = true;
	}
	void deleteEachFile(File root, int numTabs) {
	while (true) {
	File entry = root.openNextFile();
	if (!entry) {
	Serial.println("No more files");
	// no more files
	break;
	}
	for (uint8_t i = 0; i < numTabs; i++) {
	Serial.print('\t');
	}
	Serial.println(entry.name());
	if (entry.isDirectory()) {
	Serial.println("/");
	dataReader(entry, numTabs + 1);
	} else {
	// files have sizes, directories do not
	Serial.print("\t\t");
	String fileName = entry.name();
	if (SD.exists(fileName)) {
	Serial.println("Deleting the file " + fileName);
	SD.remove(fileName);
	Serial.print("File deleted");
	}
	//Serial.println(entry.size(), DEC);
	//Serial.println(line);
	}
	entry.close();
	}
	}
	bool checkSpace(uint32_t fileSize) {
	Sd2Card card;
	SdVolume volume;
	if (!card.init(SPI_HALF_SPEED, CHIPSELECT_PIN) && !volume.init(card)) {
	Serial.println("initialization failed. Things to check:");
	Serial.println("* is a card inserted?");
	Serial.println("* is your wiring correct?");
	Serial.println(
	"* did you change the chipSelect pin to match your shield or module?");
	Serial.println(
	"Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");
	return false;
	} else {
	uint32_t volumesize;
	Serial.print("\nVolume type is FAT");
	Serial.println(volume.fatType(), DEC);
	Serial.println();
	volumesize = volume.blocksPerCluster(); // clusters are collections of blocks
	volumesize *= volume.clusterCount(); // we'll have a lot of clusters
	volumesize *= 512; // SD card blocks are always 512 bytes
	Serial.print("Volume size (bytes): ");
	Serial.println(volumesize);
	Serial.print("Volume size (Kbytes): ");
	volumesize /= 1024;
	if (volumesize > fileSize) {
	return true;
	} else {
	return false;
	}
	}
	}
	void initializeDigitalPIN() {
	//set pins to output because they are addressed in the main loop
	pinMode(LATCHOUT_PIN, OUTPUT);
	pinMode(CLOCK_PIN, OUTPUT);
	}
	void setDigitalPINOut(byte variableData) {
	digitalWrite(CLOCK_PIN, LOW);
	digitalWrite(LATCHOUT_PIN, LOW);
	shiftOut(DATAOUT_PIN, CLOCK_PIN, variableData);
	digitalWrite(LATCHOUT_PIN, HIGH);
	}
	/*
	* Sample from arduino tutorial website
	*/
	void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {
	// This shifts 8 bits out MSB first,
	//on the rising edge of the clock,
	//clock idles low
	/*Serial.print("Data Before: ");
	Serial.println(myDataPin);*/
	//internal function setup
	int i = 0;
	int pinState;
	pinMode(myClockPin, OUTPUT);
	pinMode(myDataPin, OUTPUT);
	//clear everything out just in case to
	//prepare shift register for bit shifting
	digitalWrite(myDataPin, 0);
	digitalWrite(myClockPin, 0);
	//for each bit in the byte myDataOut�
	//NOTICE THAT WE ARE COUNTING DOWN in our for loop
	//This means that %00000001 or "1" will go through such
	//that it will be pin Q0 that lights.
	for (i = 7; i >= 0; i--) {
	digitalWrite(myClockPin, 0);
	//if the value passed to myDataOut and a bitmask result
	// true then... so if we are at i=6 and our value is
	// %11010100 it would the code compares it to %01000000
	// and proceeds to set pinState to 1.
	if (myDataOut & (1 << i)) {
	pinState = 1;
	} else {
	pinState = 0;
	}
	//Sets the pin to HIGH or LOW depending on pinState
	digitalWrite(myDataPin, pinState);
	//register shifts bits on upstroke of clock pin
	digitalWrite(myClockPin, 1);
	//zero the data pin after shift to prevent bleed through
	digitalWrite(myDataPin, 0);
	}
	//stop shifting
	digitalWrite(myClockPin, 0);
	}

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