A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('S')

[jfornech]

Hardware:

Board: ?Widora Air V6?
Core Installation/update date: ?20/mar/2018?
IDE name: ?Arduino IDE?
Flash Frequency: ?40Mhz?
Upload Speed: ?115200?

Description:

When i try to connect my ESP32, i got this error "A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('S')". I tried to change upload speed or the flash frequency, but nothing work.
What can i do ?
Thanks

Sketch:

*
 *  This sketch demonstrates how to scan WiFi networks.
 *  The API is almost the same as with the WiFi Shield library,
 *  the most obvious difference being the different file you need to include:
 */
#include "WiFi.h"

void setup()
{
    Serial.begin(115200);

    // Set WiFi to station mode and disconnect from an AP if it was previously connected
    WiFi.mode(WIFI_STA);
    WiFi.disconnect();
    delay(100);

    Serial.println("Setup done");
}

void loop()
{
    Serial.println("scan start");

    // WiFi.scanNetworks will return the number of networks found
    int n = WiFi.scanNetworks();
    Serial.println("scan done");
    if (n == 0) {
        Serial.println("no networks found");
    } else {
        Serial.print(n);
        Serial.println(" networks found");
        for (int i = 0; i < n; ++i) {
            // Print SSID and RSSI for each network found
            Serial.print(i + 1);
            Serial.print(": ");
            Serial.print(WiFi.SSID(i));
            Serial.print(" (");
            Serial.print(WiFi.RSSI(i));
            Serial.print(")");
            Serial.println((WiFi.encryptionType(i) == WIFI_AUTH_OPEN)?" ":"*");
            delay(10);
        }
    }
    Serial.println("");

    // Wait a bit before scanning again
    delay(5000);
}

Debug Messages:

Connecting........_____....._____....._____....._____....._____....._____....._____....._____....._____....._____
A fatal error occurred: Failed to connect to ESP32: Invalid head of packet ('S')

[beegee-tokyo]

Looks like your computer cannot see the ESP32

• Are you on MAC? Check Wiki
• Do you have the proper USB driver installed? CP2104 is the driver you need to look for Silabs drivers
• Did you try different USB cable or different USB port?

[glkeeney1951]

I got the same error with and Espressif ESP32-WROOM-32. Device Manager shows the Silicon Labs CP210x USB to UART Bridge (Com15) for my port.
The sketch verifies, but does not Upload to the board. Changing the USB port to 4 gets different error.

[jfornech]

Hello,
I fixed it by pressing "Load" button before switch the ESP32 on. The Rx/Tx leds stop to blink, so the serial port was no more use by the ESP. I tried to launch a connection, and it works .

[tlvlp]

Hi,

Although the issue is closed and the workaround works for me as well the problem still persists and I think that it could be related to writing to the Serial when the upload starts.

eg. in the above example "Invalid head of packet ('S')" might be coming from:

void setup() {
   ...
    Serial.println("Setup done");
}

In my case the message is "Invalid head of packet ('{')" and I'm using the aREST library that sends a standard json resposne to every serial input and it starts with '{'

Hopefully someone more knowledgeable than me can find a permanent solution.

[Speshal]

Hi,

Although the issue is closed and the workaround works for me as well the problem still persists and I think that it could be related to writing to the Serial when the upload starts.

eg. in the above example "Invalid head of packet ('S')" might be coming from:

void setup() {
   ...
    Serial.println("Setup done");
}

In my case the message is "Invalid head of packet ('{')" and I'm using the aREST library that sends a standard json resposne to every serial input and it starts with '{'

Hopefully someone more knowledgeable than me can find a permanent solution.

I just got my first ESP32 (ESP32 Dev board), had the same issue, held down the boot button and my sketch uploaded fine.

[Huong-nt]

ESP32-lyrat board: I fixed by press buttons while upload mode:
https://docs.espressif.com/projects/esp-adf/en/latest/get-started/index.html#upload

[tlvlp]

Yes as I've mentioned this method works for me as well but it makes it impossible to use OTA update with the device as you have to be physically present, pressing the button for the update to be able to run..

[sharatkanthi]

Press the "Boot" button on your ESP, Start uploading your code from Arduino IDE and keep "Boot" pressed till upload completes.

[tlvlp]

yes that's what the workaround is mentioned many times before, but in case the OTA (Over The Air) updates you can not physically access the device.. that is the whole point of it..

[programonauta]

Hi,, I had the same problem. I really spent a bunch of time to realize that the problem was I didn't close the serial monitor. I'm using Platform.IO, but I imagine the problem could be similar.

[lukile]

Hello there!
I had the same problem and I just found out it was because my upload speed (which is in "Tools") was set on 921600 instead of 115200.
Hope it would help :)

[Ghaith111]

hello everyone,
im an interne at a lab and i m new to programing. my tutor game me the M5stack to work on with the arduino IDE. i saw in a video that i have to install the m5stack libraries which i did.
when i go to "examples" to lunch "factory test" to be able to use the other examples on the arduino, i had a problem :
A fatal error occurred: Invalid head of packet (0xF0)
Can someone pls help ?
thank you !

[ToOpenSky]

Hello,
I fixed it by pressing "Load" button before switch the ESP32 on. The Rx/Tx leds stop to blink, so the serial port was no more use by the ESP. I tried to launch a connection, and it works .

@jfornech 👍 Thank you so much. It works now.

[cskang510]

I had the same issue with ESP WROOM32.
Thanks for your tip.
Holding BOOT button fixed it.