Exercise $11\mathrm{.}0$

The state machine shown in "state$\_$machine$\_$tut$11.$png$"$ implements a

serial command parser with the following functionality:

Start character: $\text{'}$a$\text{'}$

Escape character: $\text{'}$b$\text{'}$

Commands :

$\text{'}$c$\text{'}$ turn on display

$\text{'}$d$\text{'}$ turn off display

$\text{'}$e$\text{'}$ display payload byte in hexadecimal

Command $\text{'}$e$\text{'}$ is followed by a payload byte of one character and a

checksum byte which should be equal to the payload byte plus one.

On receipt of a valid command, the command parser responds with

"ACK

$".$

On receipt of an invalid command $($including a failed checksum$)$ the

command parser responds with "NACK

$".$

TASK: Complete the implementation of this serial command parser below.

You can use the following stdio functions to access the serial

interface:

getchar$()$

printf$()$

The following functions provided by "qutyio.h$"$ can be used to control

the display:

display$\_$on$()$

display$\_$off$()$

display$\_$hex$()$