Modify the PWM motor control code so that motor RPM changes smoothly between $100\%$ and $50\%$ and back. You can modify the case statement and add a subroutine to set the PWM through OCR$1$ register.

$1-$main.cpp

$2-$short explanation of how your code works.

#include

#define PWM$\_100255$

#define PWM$\_90230$

#define PWM$\_50128$

#define PWM$\_00$

uint$32\_$t uMsCnt, start$\_$time, current$\_$time;

void setup$()$

$\{$

$//$ Leds: RED Uno #$7($PD$7),$ GREEN Uno #$6($PD$6)$

DDRD $|=(1<<$ PD$6)$; $//$ GREEN output $($Uno #$6)<=>$ DDRD

DDRD $|=(1<<$ PD$7)$; $/*$ TBD $*///$ RED output $($Uno #$7)<=>$ DDRD

PORTD $|=(1<<$ PD$6)$; $//$ GREEN off

PORTD $|=(1<<$ PD$7)$; $//$ RED off...

$//$ Timer$1$ setup$($PWM output$)$

DDRB $|=(1<<$ PB$1)$; $//$ PWM output on pinOC$1$A $($Uno #$9)$

TCCR$1$A $=(1<<$ COM$1$A$1)|(1<<$ WGM$10)$; $//$ toggle OC$1$A on compare match, $8-$bit phase corrected PWM

OCR$1$A $=$ PWM$\_0$; $//$ start with PWM duty cycle $0\%($output low$)$

TCCR$1$B $=(1<<$ CS$11)$; $//$ prescaler$=8($PWM $16$MHz$/8*(2*255)=3,9$ kHz$,$ T$=255$ us$),$ starttimer

uMsCnt $=0$; $//$ reset ms counter

start$\_$time $=$ millis$()$; $//$ reset ms counter start$\_$time

$\}$

void loop$()$

$\{$

$//$ put your main code here, to run repeatedly:

switch $($uMsCnt$)$

$\{$

$//$ uMsCnt goesfrom $0$ to $7500$ ms$,$ to be reset on maxvalue

case $0$:

OCR$1$A $=$ PWM$\_100$; $//$ PWM $100\%$

$//$ OCR$1$A $=$ PWM$\_90$; $//$ PWM $90\%$

PORTD $|=(1<<$ PD$6)$; $//$ GREEN off

PORTD &$=$ ~$(1<<$ PD$7)$; $//$ RED on

break;

case $2500$:

OCR$1$A $=$ PWM$\_50$; $//$ PWM $50\%$

PORTD &$=$ ~$(1<<$ PD$6)$; $//$ GREEN on

PORTD $|=(1<<$ PD$7)$; $//$ RED off

break;

case $7500$: $//$ after $7\mathrm{.}5$ s back to beginning$($PWM $100\%)$

uMsCnt $=0$; $//$ reset ms counter

start$\_$time $=$ millis$()$; $//$ reset ms counter start$\_$time

break;

default:

break;

$\}//$ endswitch$()$

current$\_$time $=$ millis$()$; $//$ get current time in ms

if $($current$\_$time $>$ start$\_$time$)$

$\{$

$//$ if start$\_$time or more ms passed

uMsCnt $+=($current$\_$time $-$ start$\_$time$)$;

$//$ update ms count

start$\_$time $=$ current$\_$time; $//$ reset start$\_$time

$\}$

$\}$