With the current release of Xduino v0.11 for ARM Cortex-M3 STM32 and also future releases of other ARM mcu as well as other non-ARM mcus, here is going to be what you can call ‘Blink’ example.
Before starting, you have to compile this code along with Xduino platform libraries and load it to the board you are using. Once loaded then you can disconnect the board from the computer then connect one wire of an LED to PB7 (you can change this to other Pin on your board, make sure to also change the code) and the other to ground appropriately. Hit reset on your board and the LED should blink.
/* Xduino library initialization */
int LedPin = PB7; // as labelled on your ARM Cortex-M3 board
while(1) //loop this block