LilyGO t-call Sim800L error -2

[Bulbik1500]

Hello im using as in title lilygo t-call with build in sim800L(Firmware: Revision:1309B10SIM800L16 ) and i tried using:
https://github.com/govorox/SSLClient/blob/master/examples/Esp32-Arduino-IDE/https_gsm_SIM800/https_gsm_SIM800.ino
and im able to connet to network and get but when it comes to GET request i get Status code: -2

[RobertByrnes]

Thanks for sharing the details of your setup and the issue. The status code -2 from SSLClient typically indicates a failure during the SSL/TLS connection or the HTTP request phase. Let's break down common causes and next steps:

What Status Code -2 Means

• In SSLClient and similar Arduino libraries, status code -2 usually indicates a network or SSL handshake failure, not a standard HTTP error code.
• The error could come from:
  • Modem/network connectivity issues (but you said you can connect to the network, so less likely)
  • SIM800L not supporting certain SSL/TLS ciphers or being unable to establish a secure connection
  • Time not set correctly on the ESP32, which is required for certificate validation
  • Incorrect server address, port, or CA certificate
  • Power supply issues with the SIM800L during high current draw (e.g., during SSL handshake)

Troubleshooting Steps

1. Check Serial Output for Detailed Errors

   • Look for more verbose logs in the Serial Monitor. Sometimes libraries print additional error info before returning -2.

2. Check Time Synchronization

   • SSL/TLS certificate validation requires the correct device time.
   • Ensure you synchronize the ESP32's time via NTP or GSM before making HTTPS requests.
   • Example for setting time (before HTTP request):

     configTime(0, 0, "pool.ntp.org");
     while(time(nullptr) < SOME_REASONABLE_TIMESTAMP) { delay(100); }

3. Check CA Certificate

   • Make sure you are using the correct root CA certificate for the server you are connecting to.
   • If connecting to a public HTTPS site, extract and use the correct CA in PEM format.

4. Server and URL

   • Double-check the server URL (use https, correct port 443) and resource path.
   • Some sites (especially modern ones) require TLS 1.2 or higher, which SIM800L may not fully support.

5. Power Supply

   • SIM800L is very sensitive to voltage drops. Ensure you have a stable power supply capable of at least 2A during transmission peaks.

6. Try HTTP Instead of HTTPS

   • As a test, try switching to HTTP (if the server supports it) to see if the issue is specifically with SSL/TLS.

7. SIM800L Firmware and Support

   • SIM800L has limited and sometimes buggy SSL support. Consult the SSLClient documentation and SIM800L AT command manual for SSL limitations.

8. Check Example Code

   • Compare your code closely with the example. Sometimes a small difference (like missing CA cert, not waiting for time sync, etc.) can cause failures.

Next Steps

• Can you share the full serial log output? This will help pinpoint where the -2 is coming from.
• Confirm if you set the system time before the HTTPS request.
• What server/URL are you trying to access?
• Have you tried with HTTP (port 80) for comparison?

If you provide the serial logs and clarify the above points might be able to help narrow it down