Aim: Using interrupts to cycle through LEDs and control their brightness using PWM$.$

For this experiment, you will need to consult the usual reference documents:

LPC$824$ user manual

LPC$82$x datasheet

Alakart schematic diagram

Write the code using the peripheral support libraries $($Xpressso SDK$).$

In this experiment, we will keep the three LED configuration, but only one external switch. The three LEDs will be turned ON sequentially using a timer INT and their brightness will be cycled by pressing the external button. The external button will be connected through a pin interrupt $($PINT$).$

The main loop of the program must not do anything. It must be completely empty.

PART I

Construct a circuit consisting of three LEDs of any color you like and one external button.

Make sure that the processor system clock is configured to $30$ MHz $($you may copy the clock configuration code provided in the class example projects$)$

Configure the MRT timer such that it generates an INT every $10$ ms $.$

Write an ISR for the MRT$.$ The ISR must have a counter that counts to $50,$ turns off the current LED and turns on the next LED.

At this stage, you should get a sequencer that changes to the next LED every $500$ ms $.$

Use a chronometer to check that you really get the correct timing. $($Time $10$ complete sequences and make sure it is close to $15s=1030\mathrm{.}5s)$

Note: The clock input of the MRT is the "system clock" which is set to $30$ MHz $.$ See Appendix $1$ and also "Fig. $49$ MRT clocking" of the user manual.

Write in your report:

What values must be written to which registers so that the desired INT frequency of $10$ms can be accomplished.

Store the code for this part in a folder named $"$EX$2\_$PART$1".$

PART II

In PART I, we built a LED light sequencer. Now we will add LED brightness functionality to the light sequencer by using PWM$.$ Keep the code in PART I and add the following to it:

Connect the LEDs to the outputs of the SCT using the SWM peripheral.

Configure the SCT to generate a PWM signal such that the brightness of the LEDs can be changed.

Configure the PWM frequency to be $1$ kHz $.$

The MRT INT should still be active, and still served by the ISR as in PART I.

Every $500$ ms $,$ change the PWM duty ratio of the currently ON LED to $0\%,$ and the next LED to $60\%.($You can use more or less PWM duty ratio to get a visually pleasing brightness.$)$

As a result, we should be getting the same effect as in PART I, but the LEDs should be dimmer.

Write in your report:

How the SWM is configured so that the LEDs are now connected as PWM outputs of SCT$.$ What values must be written to which registers?

How the SCT is configured to produce $3$ PWM outputs. What values must be written to which registers?

Store the code for this part in a folder named $"$EX$2\_$PART$2".$

I want a part $2$ code.