ESP32, SD_Test.ino writing to SD

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1

I am programming SPARTKFUN VROOM Thing Plus C for use with the SD card and I am struggling with how to write a int to the SD card.

The sample code works fine with characters or text, i.e “Hello” but the FS.h code uses pointers which are not my strong point.

The SD_Test code uses appendFile(SD, “/LOW_2”, “World!\n”); to send text (“World!”) but how would I sens a integer ; replacing World! with my integer(count) does not work.

I am incrementing the integer count and I want to write it to the SD card but I am stuck. Following is my complete code

/*************
4/20/2023- STARTED WITH SPARKFUN WIFI EAMPLE CODE"SPARKFUN_WIFI.ino"
ADDED SD_Test.ino, removed un-needed code and added counter code without RTC

***********/
#include <WiFi.h>

// WiFi network name and password:
const char * networkName = "xxxxxxx";
const char * networkPswd = "yyyyyyyyyy";

#include "FS.h"
#include "SD.h"
#include "SPI.h"

const int sd_cs = 5; //Thing Plus C

int targetPin = 33;  //INCREMENT TARGETS COUNT, SEND TO SD CARD
int target;
int count;
int counter;
int counterPin = 32;  //RESET COUNTER TO ZERO

const int LED_PIN = 13;

void setup()
{
  // Initilize hardware:
  Serial.begin(115200);
  pinMode(LED_PIN,OUTPUT);
  pinMode(targetPin,INPUT);
  pinMode(counterPin,INPUT);   


  // Connect to the WiFi network (see function below loop)
  connectToWiFi(networkName, networkPswd);
  digitalWrite(LED_PIN, LOW);   //BLUE LED OFF

  Serial.println("SD test");
  if (!SD.begin(sd_cs)) {
      Serial.println("Card Mount Failed");
      return;
      }
  uint8_t cardType = SD.cardType();

  if (cardType == CARD_NONE) {
    Serial.println("No SD card attached");
    return;
  }

  Serial.print("SD Card Type: ");
  if (cardType == CARD_MMC) {
    Serial.println("MMC");
  } else if (cardType == CARD_SD) {
    Serial.println("SDSC");
  } else if (cardType == CARD_SDHC) {
    Serial.println("SDHC");
  } else {
    Serial.println("UNKNOWN");
  }

  uint64_t cardSize = SD.cardSize() / (1024 * 1024);
  Serial.printf("SD Card Size: %lluMB\n", cardSize);
/****************
  listDir(SD, "/", 0);
  createDir(SD, "/mydir");
  listDir(SD, "/", 0);
  removeDir(SD, "/mydir");
  listDir(SD, "/", 2);
  writeFile(SD, "/hello.txt", "Hello ");
  ************/
  //appendFile(SD, "/LOW_2", "World!\n");       
  //                          `readFile(SD, "/hello.txt");
/*******************
  deleteFile(SD, "/foo.txt");
  renameFile(SD, "/hello.txt", "/foo.txt");
  readFile(SD, "/foo.txt");
  testFileIO(SD, "/test.txt");
  Serial.printf("Total space: %lluMB\n", SD.totalBytes() / (1024 * 1024));
  Serial.printf("Used space: %lluMB\n", SD.usedBytes() / (1024 * 1024));
*******************/
Serial.println("FILE NAME = SPARKFUN_WIFI_SD_cleaned_code");
}

void loop()
{
  counter = digitalRead(counterPin);

  if (counter == HIGH)
  {
    Serial.println("counter == HIGH");
    count = 0;
  }

target = digitalRead(targetPin);

  if (target == HIGH)
    {   
      Serial.println("target == HIGH");
      //DateTime now = rtc.now();      
      count = count + 1;
      Serial.print("Count = ");
      Serial.println(count);     

      Serial.println("opening data fiLe");
      appendFile(SD,"/LOW_2", "count\n");

      delay(500);
    }   
}

void connectToWiFi(const char * ssid, const char * pwd)
{
  int ledState = 0;

  Serial.println("Connecting to WiFi network: " + String(ssid));

  WiFi.begin(ssid, pwd);

  while (WiFi.status() != WL_CONNECTED) 
  {
    // Blink LED while we're connecting:
    digitalWrite(LED_PIN, ledState);
    ledState = (ledState + 1) % 2; // Flip ledState
    delay(500);
    Serial.print(".");
  }

  Serial.println();
  Serial.println("WiFi connected!");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
}

void appendFile(fs::FS &fs, const char * path, const char* message) {
  Serial.printf("Appending to file: %s\n", path);

  File file = fs.open(path, FILE_APPEND);
  if (!file) {
    Serial.println("Failed to open file for appending");
    return;
  }
  if (file.print(message)) {
    Serial.println("Message appended");
  } else {
    Serial.println("Append failed");
  }
  file.close();
}

void readFile(fs::FS &fs, const char * path) {
  Serial.printf("Reading file: %s\n", path);

  File file = fs.open(path);
  if (!file) {
    Serial.println("Failed to open file for reading");
    return;
  }

  Serial.print("Read from file: ");
  while (file.available()) {
    Serial.write(file.read());
  }
  file.close();
}
2

I am not familiar with the library that you’re using. You are saying that you can send texts without any issue, but facing problems with sending int. So, I guess, the functions that you are using are only capable of accepting strings, not integers. I request you to look inside the .cpp file of the library. Thus you can check if there is any function for integers. If not, you will need to perform an integer to ASCII conversion.

3

The libraries are the ones used in the example program in your tutorial for the SPARKFUN VROOM thing plus C. The example sketch is SD_Test.ino.

Please review the SPARKFUN examples and let me know if you can think of a solution.

4

Try converting your line to a string with sprintf first, then writing to the SD card.

Here’s some discussion on how: https://www.programmingelectronics.com/sprintf-arduino/

Edit… take a closer look at the functions here.

#include <string.h>

#include <stdlib.h>