Is there a limit to the length of a string when it is uploaded to the RTDB?

[ProyectoOVO]

Hello, im using the Firebase-ESP-Client lib, but before i was using the FirebaseESP32.h, the thing is that with the other library i was able to upload a VGA image (in base64) to the RTDB, but now i cannot, it doesnt arrive to firebase (the esp-32cam has no problem encrypting in base64 a vga image), but with the same function i can upload a QVGA image, so the function works. I was wondering if is there a limitation on the bytes or length when using strings? Because is strange, i dont think is a firebase console limitation because as i said i was able to upload the string without problem with the other lib.

[mobizt]

Conversion large image data to base64 string in this low memory device is not efficient and may limited due to Heap fragmentation.

I recommend Blob and Files that already implemented in this library.

The BLOB and File will be converted to base64 encoded string on the fly when you store (upload) data to RTDB database and converted back from base64 string to BLOB and File when restore (download) data from RTDB database.

In your case, you can use send image data directly via Blob function or save it to file and send it later via File functions.

The base64 string stores in the RTDB database using Blob and File functions will be prepended with 12 bytes of blob signature blob,base64, and 12 bytes of file signature i.e., file,base64, for no padding and File,base64, for 1 padding and fIle,base64, for 2 padding.

The padding of file signature is for decoded size calculation. The padding is not included in blob signature as the base64 string will be converted back to dynamic array data without decoded size calculation.

If you want to read this signature prepended base64 string from RTDB database manually instead of using Blob and File functions, you need to remove the first 12 bytes signature from the data before decoding.

[mobizt]

Both FirebaseESP32 and Firebase-ESP-Client libraries use the same source code for RTDB functions.

The limitation is not because the library limit but Heap fragmentation I mentioned above.

[ThaiLe-gt]

Hello @mobizt. I have the same problem uploading long strings or blobs as you suggested. My data in Firebase always lacked a lot of data. Could you help me to solve it?

By Blob

    String photoPath = "/iot/esp32cam/photo";
    // json.set("photo",Photo2Base64());
    camera_fb_t * fb = NULL;

    fb = esp_camera_fb_get();  
    if(!fb) {
      Serial.println("Camera capture failed");
    }
    uint8_t* file = fb->buf;

    if (Firebase.setBlob(fbdo, photoPath, file,sizeof(file))) {
      Serial.println("push data successfully");
    } else {
      Serial.println(fbdo.errorReason());
    }
     esp_camera_fb_return(fb);

[mobizt]

@ThaiLe-gt

You cannot use sizeof with pointer (uint8_t*).

It will always return the size of pointer (4).

You should use fb->len to get the image size instead.

From image you posted above, the decrypt data is only four bytes long i.e., 0xff 0xd8 0xff 0xe0.

[ThaiLe-gt]

oh. it works 👯‍♂️
Thanks, @mobizt so much!

[samgonzaga]

Good sir, @ThaiLe-gt sorry to open up this thread discussion again when it was answered already by the owner. I just wanted to ask how were you able to connect your ESP32 Camera to Firebase RTDB? I'm trying to connect my ESP32 Cam to firebase and retrieve data from it but I am getting errors such as "'class FirebaseData' has no member named 'to.' So far I have not been able a source of fix for it.

Is it possible to see the code on how you connected it? Thank you.