Micro

con

troller

A

Hitac

hi

SH  

micro

con

troller

running

at

  MHz

is

used

to

in

terface

to

a

host 

Its

   bit

arc

hitecture 

along

with

its

   bit

analog to digital

con

v

erters

and

its

lo

w

cost

mak

e

it

an

ideal

solution 

F

or

ease

of

in

tergration 

a

Hitac

hi

ev

aluation

b

oard

w

as

used 

It

con

tains

circuitry

for

all

of

the

RS    

lev

el

con

v

ersion

as

w

ell

as

the

reset 

The

I

and

Q

c

hannels

are

connected

to

the

micro

con

troller s

A D

inputs 

along

with

the

start

and

stop

phototransistor

signals

as

logic

lev

els 

Em

b

edded

Co

de

The

em

b

edded

co

de

w

as

written

in

C

for

the

SH  

micrcon

troller 

It

w

as

compiled

and

burned

in

to

an

EPR

OM 

The

co

de

is

structured

in

suc

h

a

w

a

y

as

to

utilize

man

y

of

the

functional

blo

c

ks

of

the

SH   

The

I

and

Q

c

hannels

are

digitized

b

y

con guring

the

analog to digital

con

v

erter

of

the

SH  

to

scan con

v

ert

c

hannels

one

and

t

w

o 

Once

con gured

and

started 

the

scan

con

v

erter

will

sample

at

the

fastest

sp

eed 

con

tin

ually

up

dating

the

registers

with

the

new

est

results 

Up

on

reset 

the

micro

con

troller

b

egins

scanning

the

t

w

o

analog

c

hannels 

determining

a

v

alid

scan

in

terv

al

to

b

e

b

et

w

een

the

 start 

and

 stop 

phototransistor

signals 

It

 rst

tak

es

a

calibration

scan 

a

v

eraging

all

of

the

samples

to

determine

a

baseline

for

the

signals 

It

then

sits

in

a

holding

mo

de 

w

aiting

for

the

con guration

information

from

the

host 

The

con

troller

comm

unicates

to

the

host

using

RS    

serial

proto

col 

sending

bits

without

parit

y

at

a

baud

rate 

The

angle

is

tak

en

as

the

time

on

a

   bit

timer

that

has

elapsed

since

the

 start 

phototransistor

pulse 

The

timer

is

reset

b

efore

eac

h

scan 

A

 T 

c

haracter

is

sen

t

from

the

host 

signifying

the

setting

of

the

threshold 

Tw

o

b

ytes

are

then

sen

t

for

the

threshold

v

alue 

high

b

yte

 rst 

A

 W 

c

haracter

is

sen

t

from

the

host

to

signify

that

the

follo

wing

b

ytes

determine

the

w

ait

time 

This

is

the

time

after

a

v

alid

start

signal

b

efore

data

should

b

e

considered 

This

mak

es

sure

that

the

re ection

from

the

phototransistor

housing

isn t

con

triv

ed

to

b

e

a

data

p

oin

t 

If

a

 D 

is

sen

t 

the

pro

cessor

en

ters

in

to

a

debug

mo

de 

This

will

prin

t

all

of

the