Part $($d$)$: Write the function encode$\_$letter

encode$\_1$etter:

parameters: one byte, pushed onto the stack by the caller, pass$-$by$-$value

return value: $125$

This document began by describing a way of encoding letters as LED light patterns,

with the example of "HELLOWORLD" given. Although you're not yet ready to display the

whole message, your task for this part is to take a single upper$-$case letter and to

convert it into the correct pattern $($lights and duration$).$

Towards the bottom of a$2-$signalling$-$asn you will find the label PATTERNS,

followed by an upper$-$case alphabet $-$ one letter per line $-$ with information on

LED$/$duration encodings. For example, the first non$-$comment line below PATTERNS

is:

$.db{A}^{**},**.\mathrm{.}00..,1$

which is to be interpreted as follows:

This line is for the letter $"$A$"$;

LEDS $01,02,05$ and $06$ are off in this pattern;

LEDS $03$ and $04$ are on in this pattern;

The lighting pattern is to appear for about one second.

Right below appears this line:

$.$db $"",".$o$..$a$.",2$

which is to be interpreted as follows:

This line is for the letter $"B^2$;

LEDS $01,03,04,$ and $06$ are off in this pattern;

LEDS $02$ and $0405$ are on in this pattern;

The lighting pattern is to appear for about one$-$quarter of a second.

So on and so forth.

The only other entry that requires some special explanation is the very last. It appears

here as something which you may choose to check $-$ i$.$e$.$ if you are looking for a letter,

but find the dash $(*-")$ then something has gone wrong with the parameter value.

$($When testing your code, the evaluators will only use upper$-$case letters. However,

you cannot be sure how you yourself will accidentally test your code!$)$

Given the letter pushed onto the stack, your function is to determine the encoding for

the letter as would be given to leds$\_$with$\_$speed $($i$.$e$.$ a byte value$),$ and this returned

in register $225.($That is$,$ you are not to call leds$\_$with$\_$speed from within

encode$\_$letter$)$ Make use the functions you have written earlier in this assignment

to complete the function, as well as other operations. For example, the value returned

in $125$ for $"$A$"$ would be $0b11001100$ or excc; the value returned in $125$ for ${?}^2{B}^{*}$ would

be $$ be$1010$ or $Ex12.$

Some code is provided for you at the label test$\_$d which you may use to try out your

work after writing code for these two functions. The video described earlier in this

document shows the expected behavior of test$\_$d$.$