C28335 Controller External mode communication keeps 'freezing'

Hi All,

I am using C28335 Experiment kit and Matlab Simulink R2015a and CCSv5.5 to control dual stage converter (boost converter at fsw 20kHz and inverter at fsw 4 kHz). When I test just a boost converter, everything works fine in External mode. No problem there.

But when I test boost converter and inverter combined, at certain voltage level (e.g. Vdc inverter > 100 V) External mode and Simulink stops responding. I cannot even stop communication and I have to unplug USB to stop it.

What can be the source of this? A noise from the inverter, ADC channels, poor LC filter characteristics, etc. A serial communication should be robust enough. But are there any options/settings to make serial communication more robust... If I assume nose is the problem.

Update: I changed inverter switching frequency to 6 kHz and still controller disconnects