Resolve TLS Issue for GPS Transmission -Fixing HTTP payload - 05/03/2026 03:11 EST
Budget: £10 – £20 GBP
I’m working on a project using the AVR-IoT Cellular Mini (Sequans Monarch 2 modem) where I customized the Arduino-based firmware myself to periodically send GPS latitude and longitude data to my backend (BE) over HTTPS.
The goal is to push GPS data (lat/long + timestamp) to a REST API endpoint within a specific time interval and verify that the data is successfully received and visible on the backend.
However, I’m currently blocked by a TLS issue when trying to configure the CA certificate for HTTPS. When I attempt to add the root CA certificate (ISRG Root X1 – Let’s Encrypt) into the device/modem,
I receive an error stating: “CA certificate input too long”
Because of this: The TLS handshake fails. The HTTPS request does not complete. The endpoint is never reached. No GPS payload appears in the backend.
What I have done so far: Generated and included the ISRG Root X1 certificate in PEM format. Attempted to load it into the modem for server verification. Built my own HTTP POST payload in Arduino to send JSON data (latitude, longitude, timestamp). Confirmed that the payload structure itself is correct. The issue appears specifically during certificate loading / TLS configuration. What I need to resolve: The correct way to store or upload the CA certificate into the Sequans modem (considering size limitations).
Whether the certificate must be converted from PEM to DER format. How to properly configure TLS so the endpoint can be reached.
Ensure the HTTPS POST successfully delivers the GPS data to the backend. Ultimately, I need the HTTPS endpoint issue resolved so that I can verify my custom Arduino firmware correctly transmits GPS data to the backend within the required time frame. Any guidance on handling CA certificate size limitations or proper TLS configuration on the AVR-IoT Cellular Mini would be greatly appreciated.
The goal is to push GPS data (lat/long + timestamp) to a REST API endpoint within a specific time interval and verify that the data is successfully received and visible on the backend.
However, I’m currently blocked by a TLS issue when trying to configure the CA certificate for HTTPS. When I attempt to add the root CA certificate (ISRG Root X1 – Let’s Encrypt) into the device/modem,
I receive an error stating: “CA certificate input too long”
Because of this: The TLS handshake fails. The HTTPS request does not complete. The endpoint is never reached. No GPS payload appears in the backend.
What I have done so far: Generated and included the ISRG Root X1 certificate in PEM format. Attempted to load it into the modem for server verification. Built my own HTTP POST payload in Arduino to send JSON data (latitude, longitude, timestamp). Confirmed that the payload structure itself is correct. The issue appears specifically during certificate loading / TLS configuration. What I need to resolve: The correct way to store or upload the CA certificate into the Sequans modem (considering size limitations).
Whether the certificate must be converted from PEM to DER format. How to properly configure TLS so the endpoint can be reached.
Ensure the HTTPS POST successfully delivers the GPS data to the backend. Ultimately, I need the HTTPS endpoint issue resolved so that I can verify my custom Arduino firmware correctly transmits GPS data to the backend within the required time frame. Any guidance on handling CA certificate size limitations or proper TLS configuration on the AVR-IoT Cellular Mini would be greatly appreciated.
Related categories:
Linux
Electronics
Microcontroller
GPS
Arduino
JSON
Backend Development
Network Security
API Integration
REST API