Hello Gijs,
Basically, there is not much that you can do about this in simulink. The more data that has to be transferred in external mode (=more scopes) results in slower update rates. If it is possible at all, i would recommend using target scopes. This shows the information directly on a display connected to the target PC.
If there is no display available on your target device, you can choose to log your signals or to send the data via UDP to a UDP listener model that you can create in a secondary simulink model or another program (e.g., labview) if you want to use the data interactivly.
Logging signals in real-time is different than normal (to workspace blocks don't work), you can instead connect an out block (those from submodels) to your signal on the highest simulink model level. This will add your data to the tg.OutputLog structure field. You can set the amount of data collected in the simulation options under code generation tab.
Hope this helps,
Dennie
