Using MPLAB $-$ ADC$\_$Controlled$\_$Pulse

Description:$-$ This program reads the Analog voltage from the potentiometer on input $"$AN$0($RA$0)"$ as a $10-$bit value and turns $"$ON$"$ the LED connected to pin $"$RB$0"$ with an on$-$time proportional to the ADC value using a For Loop. As you adjust the potentiometer $($i$.$e$.$ ADC value$)$ this will vary the ON Vs OFF time of the LED which is used to implement a variable brightness on the LED. This is effectively a PWM $($Pulse Width Modulated$)$ waveform.

Instructions:$-$

$1.$ Create a macro name for the LED:$-$

E$.$g$.\backslash$#define LED RB$0$

$2.$ Create a macro name for ON and OFF :$-$

E$.$g$.\backslash$#define ON $1$

$\backslash$#define OFF $0$

$3.$ Use the macros listed above in your program.

$4.$ Setup RB$0$ pin as a Digital Output.

$5.$ Setup AN$0/$RA$0$ pin as an Analog input.

$6.$ Setup the ADC as follows $($see ADCON$0\backslash$& ADCON$1$ registers on pages $114/115$ of the PIC$16$F$188$ Datasheet$)$:$-$

ADCON$0$

$-$ Setup "ADCS $\backslash (<mn>1</mn>$: $0>\backslash )"$ bits to select the internal RC oscillator

$-$ Setup $"$CHS$<mn>2</mn>$:$0>"$ to select Channel $0($i$.$e$.$ RA$0/$AN$0)$

$-$ Setup "ADON" bit to turn on A$/$D module

ADCON$1$

$-$ Setup "ADFM" bit to select Right Justified result

$-$ Setup "ADCS$2"$ bit as disabled

$-$ Setup $"$VCFG $\backslash (<mn>1</mn>$: $0>\backslash )"$ bits to use AVDD and AVss

$7.$ Create a $16-$bit variable called "adc$\_$val", to store the $10-$bit adc result.

$8.$ Inside a continuous loop, start an $\backslash ($ A $\backslash$bar$\{$D$\}$ C $\backslash )$ conversion by writing to the $"$GO$\_$DONE" bit.

$9.$ Wait until the ADC conversion has completed.

$10.$ Align the $10$bit adc value from ADRESL $\backslash$& ADSREH inside the variable "adc$\_$val".

$11.$ Use a FOR loop, that counts from $0$ to $1023,$ to turn on the LED connected to RB$0$ when the value of the For Loop iteration count value $($e$.$g$.$ i$)$ is less than the ADC value, and turn it off when value of the For Loop iteration counter is greater than the ADC value. This is in effect produces a variable on$-$time that is proportional to the ADC value and implements a of implementing Pulse Width Modulation $($PWM$).$ This produces a variable brightness on the LED.

$12.$ The PWM waveform can be viewed by double clicking the Oscilliscope while running a simulation. The waveforms shown below illustrate a Low$-$Duty cycle PWM cycle with low brigthness on the LED, while the Analog Input voltage is close to $0$ V $.$ Also, shown is a High$-$Duty cycle PWM waveform with an Analog Input Voltage close to $5$V$.$

$13.$ Add comments to your code $($marks lost for no comments$).$

$14.$ Ensure all code is properly indented $($i$.$e$.$ marks lost for no indentation$).$

Inputs:$-1($i$.$e$.$ AN$0($RA$0))$

Outputs:$-1($i$.$e RB$0)$