Kangaroo pet - Reset Circuit; 一 Battery Monitoring; 一 Touch Panel; LED Display

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11

3.

circuit

description

(cont.)

ED

pump

battery

as

soon

as

the

pump

is

plugged

into

the

charger

base,

even

if

the

latch

v

was

not

activated

and

the

ON

switch

was

not

pushed.

Removal

of

power

to

the

microprocessor

and

the

rest

of

the

pump

circuits

is

accomplished

by

asserting

port

PCO.

This

turns

off

the

latch

and

FET

Q18,

killing

power

to

all

circuits

except

for

Q10

and

U9.

Reset

Circuit

The

microprocessor

may

receive

a

low

input

on

the

RESET

line

for

three

reasons.

The

first,

as

seen

earlier,

is

the

activation

of

the

latch

circuit.

Power

applied

to

the

pump

circuit

will

result

in

a

pulse

generated

by

R12

and

C11.

U12

is

a

watchdog

timer

and

power

monitor.

The

microprocessor

generates

a

negative

going

pulse

every

250

milliseconds.

This

pulse

train

resets

a

timer

in

U12.

If

this

timer

is

not

constantly

reset,

U12

will

generate

a

pulse

at

its

output

which

will

reset

the

microprocessor.

U12

also

monitors

its

supply

voltage.

If

its

supply

drops

below

approximately

4.5

VDC,

U12

will

generate

a

reset

pulse

to

the

microprocessor.

Diode

D9 and

capacitor

C43

somewhat

isolate

U12

power

from

the

5

VDC

buss.

Battery

Monitoring

Resistors

R5

and

R6

divide

the

battery

voltage

by

2;

this

voltage

is

then

converted

by

the

A/D converter

into

an

eight

bit

representation

of

one

half

of

the

battery

voltage.

The

eight

bits

are

read

serially

by

the

microprocessor

using

ports

PC7,

PC6,

and

PDO

every

500

milliseconds

(or

every

other

resetting

of

the

watchdog

timer

U12).

Software

in

the

microprocessor

determines

when

the

battery

needs

to

be

quick

charged.

If

quick

charging

is

necessary,

port

PC5

signals

the

charger

base

(isolated

by

optoisolator

.

U11)

to

deliver

quick

charge

current.

Så

Touch

Panel

The

touch

panel

is

connected

to

the

pump

circuit

board

with

connector

J5.

The

panel

is

arranged

in

a

3x3

matrix,

with

the

rows

being

driven

by

microprocessor

ports

PB1,

PB2

and

PB3.

Microprocessor

ports

PB4,

PB5

and

PB6

read

the

column

information.

Software

in

the

microprocessor

decodes

the

row/column

information

and

generates

a

unique

byte

to

represent

each

switch

in

the

matrix.

It

should

be

noted

that

the

ON

key

is

independent

and

not

part

of

the

matrix.

Microprocessor

ports

PB4,

PB5

and

PB6

also

read

switch

SW1

when

this

switch

is

driven

by

PBO.

Switch

SW1

is

used

to

select

the

language

for

messages

displayed

on

the

LEDs.

Diodes

D4A,

D4B,

D18A, D18B,

D12,

D13A

and

D13B

isolate

parallel

lines

from

each

other.

Switch

debouncing

is

accomplished

in

software.

LED

Display

LEDs

DP4,

DP3,

DP2

and

DP1

are

used

to

display

feeding

profile

information

and

error

messages.

Microprocessor

ports

PB3,

PB2,

PB1

and

PBO

drive

FETs

Q16,

Q15,

Q14

and

Q13

respectively.

The

FETs

allow

a

greater

current

flow

to

the

LED

segment

common

connections

than

possible

with

the

microprocessor

I/O

ports.

Segment

information

is

driven

by

port

A

of

the

microprocessor.

These

I/O

lines

are

capable

of

sinking

enough

current

to

drive

the

display

segments.