.Modelica_DeviceDrivers.EmbeddedTargets.STM32F4.Examples.STM32F4_Discovery.BlinkGPIO_EXTI .Modelica_DeviceDrivers.EmbeddedTargets.STM32F4.Examples.STM32F4_Discovery.BlinkGPIO_EXTIBlinkGPIO_EXTI is a model configuring interrupt on falling edge on GPIO Line 0. Since Modelica is not able to generate code for the callback function, the user has to edit code here manually. In the callback function all User LEDs (port D pin 12 - 15) are toggled. As a result, the LEDs are toggled when the blue user button is released. Use this model to see if your Modelica tool can export code for STM32F4 MCUs..
STM digital pins 12 - 15 on port D corresponds to digital pin D12 - D15 on the STM32F4-Discovery. If desired, you can connect an external LEDs to this PINs, with a suitable resistor in-between (perhaps 220Ω). Connect the other PIN on the LED to ground.