more extensive APIs for additional peripherals and board features, but are
usually less generic and vendor-specific.
+=== accessing registers under CMSIS
+When you use CMSIS, you don't need to know the address of any register. That implies that
+you don't need to use `#define` directive to give names for the registers as in experiment-1.
+All the definitions are in _lpc17xx.h_ which is included at the beginning of your source file when
+a new CMSIS project is opened.
+You need to know two names to access a register:
+. the name of pointer to the structure instance.
+. The element of structure element:
+For GPIO, the name of pointer to the structure instance is:
+You can access different registers for each GPIO.
+The three registers used in experiment-1 are (regardless whether your pin is in port0,1,2,3 or 4):
+To control the direction of pins in port-2, you should use the following:
+To set pins in port-1, you should use the following:
+=== Connecting external LEDs
+.What is the maximum voltage it can tolerate.
+.If the output voltage is higher than the LED max voltage, what you can do?
+.It should be connected to an output GPIO pin.
+GPIO is available in all of the I/O pins. A GPIO is pin that can be used as a digital input or digital output pin.
+Clearly you need a command to choose the direction of the pin (whether it is used as input or output).
+In this experiment we will choose the direction to make the required pin GPO (general purpose output).
+In this case (GPO), you need a command to set this output pin to HIGH (1) and a command to Clear it to LOW (0).
-=== Import CMSIS Libraries
+. Connect the LEDs using a proper current limiting resistor.
+==== Import CMSIS Libraries
. Run LPCXpresso IDE. Choose a new workspace, e.g. `cmsis_workspace`.
. Keep both projects selected: `CMSIS_CORE_LPC17xx` and
`CMSIS_DSPLIB_CM3`, and click _Finish_.
Blink 4 External LEDs
+in the source file of your project write a code to make it looks like that a light is scrolling through your 4 LEDs.
+You can achieve that by turning LEDs ON sequentially.