Hi,
I'm using the Asset Tracker V2 program, running on my nRF9160DK with nRF Connect SDK v2.4.1.
I've modified the program to read in a UART packet, which is passed to various modules before being encoded in json and sent to the nRF Cloud via MQTT. The data flow is very similar to the UI module, which sends data immediately on a button press detection, provided there is a cloud connection.
The program works well for small MQTT messages of around 200bytes of json data. However I need to send more information in these messages, which increases the data size to around 400bytes. When I try to send messages of this size, I get a hard fault on my system with the error USAGE FAULT, unaligned memory access and zephyr fatal error. Sometimes I don't get a fault at all and the system just hangs until the watchdog resets it.
I'm not familiar with what the fault relates to: is it a lack of memory? I've trying allocating more memory to the data, cloud and modem modules, but the problem remains.
Could anyone provide some insight into what I should be doing to send larger MQTT messages? Am I running out of memory? Should I be freeing up memory? Is there a MQTT message size limit for the drivers developed that anyone is aware of?
Appreciate your help!
Chris
