spiffs_write_byte.cpp

Go to the documentation of this file.

/**
 * ESP32 S3: write a single 8-bit integer to SPIFFS (root).
 * Standalone .cpp — no PlatformIO project; add to your build as needed.
 */
 
#include <Arduino.h>
#include <SPIFFS.h>
 
static const char* FILE_PATH = "/value.bin";
static const uint8_t VALUE_TO_WRITE = 31;  // change as needed
bool success;
 
void setup() {
    Serial.begin(115200);
    delay(500);
    // Wait for serial (USB CDC) so output and user are ready before burning
    while (!Serial) {
        delay(10);
    }
    delay(500);
 
    if (!SPIFFS.begin(true)) {
        Serial.println("SPIFFS mount failed");
        return;
    }
 
    File f = SPIFFS.open(FILE_PATH, "w");
    if (!f) {
        Serial.println("Failed to open file for writing");
        SPIFFS.end();
        return;
    }
 
    size_t written = f.write(&VALUE_TO_WRITE, 1);
    f.close();
 
    if (written != 1) {
        Serial.println("Write failed");
        SPIFFS.end();
        return;
    }
    Serial.printf("Wrote byte %u to %s\n", (unsigned)VALUE_TO_WRITE, FILE_PATH);
 
    // Read back to verify
    File fr = SPIFFS.open(FILE_PATH, "r");
    if (!fr || fr.size() < 1) {
        Serial.println("Read-back failed: could not open or empty file");
        SPIFFS.end();
        return;
    }
    uint8_t readBack = 0;
    size_t n = fr.read(&readBack, 1);
    fr.close();
    SPIFFS.end();
 
    if (n == 1 && readBack == VALUE_TO_WRITE) {
        Serial.printf("Read-back OK: %s contains %u\n", FILE_PATH,
                      (unsigned)readBack);
        success = true;
    } else {
        Serial.printf("Read-back FAIL: got %u (expected %u)\n",
                      (unsigned)readBack, (unsigned)VALUE_TO_WRITE);
        success = false;
    }
}
 
void loop() {
    if (success) {
        Serial.printf("Burn in succeeded: ID %u\n", (unsigned)VALUE_TO_WRITE);
    } else {
        Serial.println("Burn in failed");
    }
    delay(500);
}