ESP32-S3 + SIM7672G: SSL connection takes too long using SSLClient library (over 1 minute)

Wireless and IoT RF and Wireless
1

Hello,

I’m working on a project using an ESP32-S3 connected to an LTE modem (SIM7672G). I’m using the SSLClient library to establish an SSL connection for MQTT communication.

However, I’m facing an issue:

The SSL connection takes about 1 minute to establish when using the SIM7672G modem.

Interestingly, when I switch to another modem, the SIMCOM A7672G, using the exact same code and setup, the SSL connection is established almost instantly.

Details:

  • Both modems (SIM7672G and A7672G) are similar in specs.
  • I’m not using AT commands for SSL or MQTT — the ESP32 handles the SSL stack directly via the SSLClient library.
  • I did test AT commands for SSL and MQTT as a workaround, and while it works, it’s not suitable for my project as I require MQTT to run through the ESP32 stack, not the modem.
  • The network signal and SIM card are the same in both cases.

My Questions:

  1. Why might the SIM7672G be significantly slower in establishing an SSL connection compared to the A7672G?
  2. Is there something specific in the SIM7672G that could affect TCP/SSL performance?
  3. Is there any known compatibility issue between SIM7672G and the SSLClient library or ESP32-S3?

I’d appreciate any insights or suggestions on debugging or optimizing this setup.
If needed, I can also share code snippets.

Thanks!

3

Are both these modem’s running the latest firmware?

SIM7672: SIM7672X Series

SIM7672 platform are based off Qualcomm’s 216 LTE IoT modem..

A7672G: A7672G

A7672G is based off ASR Micro: ASR1603

Regards,

2 Likes
4

Yes both running on same firmware.

This is weird because I saw same issue on SIM7670G too.

While I have A7672G, and SIM7000G modem too and both are running fine with same firmware.

As i am doing SSL through ESP32, it is not making sense to me.

Thanks,
Rushik

5

Sorry one more question, since i have SSL capabilities on LTE itself. Is there any way to do SSL configuration with AT command and other connections like mqtts and https are done on esp32?

6

Have you looked at this project in your research? GitHub - vshymanskyy/TinyGSM: A small Arduino library for GSM modules, that just works

Looking thru their git log, they do have native SSL Support for these models..

Regards,

7

Hi,

Yes I have used TinyGsm and tried to use, A7672 implementation in this library. But it doesn’t work.