Simulink Code Generation with External C Code

Hi,

I use Simulink code generation for C2000 systems. I have developed my model in simulink to control power flows using basic power converters.

I want now to send some data to a cloud using GPRS data. To do so, I created a C code with different AT commands. Everything works well.

I am now trying to integrate power flows control loops with the GPRS data sender into one system. Unfortunately, as soon as I start executing loop with external C code (for GPRS), I start having problems. I use System Update block for this. As soon as my system starts executing this C code, other processes (ADC reading, PWM control) stop working for as long as the external C code execution is terminated (sometimes few seconds). Within this period all my voltages collapse.

Does anyone know how to obtain parallelisation with external C code? Such that my voltage control tasks have higher priority than external C code?