Switch Control and Time Delay - Keypad

2016

Lab3

SWITCH
CONTROL
AND
TIME
DELAY

ARIEL
TONATIUH
ESPINDOLA
PIZANO

1459342

Microcontroller Units Tongji University 2

Switch Control and Time Delay

1. LEDs and switches
2. Keypad and LEDs
3. Keypad and 8-segment LED

Objective

The aim of this practice is to understand how the switches, keypad-16 and 8-segment led work
with the MC9S08AW60. Use the C language and Assembly language to develop the code.

1. LEDs and switches

Write a program, with more controls of Switches/LEDs, using delay subroutine to control the
timing. Debug and run with the Lab board.

For example: Use two switches to control two LEDs
• if one of the two switches are closed, the two LEDs wink in turn
• if both switches are opened, the LEDs are always off
• if both switches are closed, the LEDs are always on

1.1 Algorithm

In order to do the wink, it is necessary to figure out how long the LEDs will stay turned on and
turned off. To do so, the first given parameter is the Bus Clock Frequency which is one-half the
CPU Clock Frequency. According to the MCU’s datasheet, the 𝑓" bus frequency is set at 4MHz
after reset. That means that it takes 0.25
µμ 𝑠 long per cycle.

Figure 1.1.1.- Debugging the C code with the Assembly component.


Time delay

The calculation of time delayed will be so that the number of machine cycles spend the time
required (e.g. 500ms). If we have a loop that spends 50 machine cycles per iteration where it
iterates from 0 to 79. In total we have 50x80=4000 machine cycles spent.

If we want to delay 1 second according to the 𝑓" = 4𝑀𝐻𝑧 means that 4000,000 machine cycles
must be spent. This can be solved by nesting the loop of 4000 cycles (80 iterations) in an outer
loop of 1000 iterations to finally get the 4M machine cycles.

Wink in turn

To alternate the blinking between two LEDs can be done by setting them as a complement each
other. For instance, if LED0 = high then LED1 = low and vice versa.

Step by step algorithm

1. Setup the PORT of MCU which is going to be used.
2. Read the PORT and get just the input pins. (AND operation suggested)
3. If two switches PTAD4 and PTAD3 are closed, then PTAD7 and PTAD6 always on.
4. If two switches PTAD4 and PTAD3 are opened, then PTAD7 and PTAD6 always off.
5. If two switches PTAD4 or PTAD3 are closed, then PTAD7 and PTAD6 wink in turn.
6. Back to the step 2.

Pseudo-code
If(inputs == ‘closed’)
Then
alwaysON();
else (inputs == ‘opened’)
Then
alwaysOFF();
else
if(input1 == ‘closed’ or input2==’closed’)
Then
Wink();
end

Figure 1.1.2.- Flow chart of the algorithm described above.

Start

Read

PORT
closed

Both
ON

opened

no

yes

Both
OFF

yes

no

Wink


Implementation in C language for the Lab3.1:

#include <hidef.h> /* for EnableInterrupts macro */
#include "derivative.h" /* include peripheral declarations */
void delay_ms(int delay){
int i,j;
for(i=0; i<delay; i++){
for(j=0; j<80; j++);
}
}
void wink(int delay){
PTAD_PTAD6 = ~PTAD_PTAD6;
PTAD_PTAD7 = ~PTAD_PTAD6;
delay_ms(delay);
}
void alwaysOn(){
PTAD_PTAD7 = 0;
PTAD_PTAD6 = PTAD_PTAD7;
}
void alwaysOff(){
PTAD_PTAD7 = 1;
PTAD_PTAD6 = PTAD_PTAD7;
}
void main(void) {
//EnableInterrupts; /* enable interrupts */
unsigned char COND = 0x00;
PTADD = 0xF0;
PTAD = 0xFF;
SOPT = 0x53;
for(;;) {
COND = 0x0F & PTAD;
switch(COND){
case 0x03: //0011
alwaysOn();
break;
case 0x0F:
alwaysOff();
break;
default:
if(COND == 0x0B || COND == 0x07)
wink(1000);
break;


}
} /* loop forever */
}

2. Keypad and LEDs

Write a program to detect key-pressing, and change LEDs’ status according to the key position.
This means that a pressed key must be detected by its coordinates and then encoded to 4 bits in
order to show the result in 4 LEDs.

2.1 Algorithms

There are two functions, one to find the coordinates of the pressed key and other to encode the
result from a combination of 16 possible keys (input) to 4 bits(output).

Row-detection

The idea is sending a logic 0 to every single pin of the PORT where is connected the Keypad in
order to detect the column as rotating the zero to the left N times, where N stands for the number
of rows.

Encoding

Once we have the coordinate of the pressed key, it must be encoded to 4 bits to the purpose of
being showed up by the LEDs. Since we are dealing with a 16-keyboard, the encoding is as
follows:
Figure 2.1.1.- This logic diagram only illustrates symbolically the encoding made by the look-up
table. The binary encoder is not actually implemented in the assembly code.
Figure 2.1.2.- Depiction of the Keypad coordinates in Hexadecimal. Image taken from Lecture 5-
2 PPT, slide 12.
0
EE
1
DE
2
BE
3
7E
4
ED
5
DD
6
BD
7
7D
8
EB
9
DB
A
BB
B
7B
C
E7
D
D7
E
B7
F
77
2/
→ 𝑛

Encode

output:
𝑛
𝑏 𝑖𝑡𝑠
input:
2/

𝑏 𝑖𝑡𝑠


Row-detection algorithm step by step:

1. Setup PORTF of the MCU
a. Higher bits as inputs (columns)
b. Lower bits as outputs (rows)
2. Initialize the port (Set the whole port to logic one 0xFF)
3. Read the PORT
4. Check for key pressed
a. Take the higher bits
b. Drop the lower bits
c. In assembly would be: CBEQA #$F0, NO_KEY_PRESSED
5. If no key pressed, then go back to step 2.
6. If key pressed, continue to step 7.
7. Rotate a logic 0 bit from PORTF0(right) to PORTF3(left)(4 rows) once.
8. Do the step 3 and 4.
9. If no key pressed, go back to step 7.
10. If key pressed detected (higher bits), the key value has been founded then return the value
of PORTF.
11. Encode
Look-up table algorithm step by step (encoding):

1. Define a table as shown in the Figure 2.1.2.
2. Initialize the H:X index register of the MCU from #$0000 (offset)
3. Take the value out from KBTABLE according to the position pointed by H:X register.
4. If the taken value is #$00, return #$FF indicating that the fetched value is not defined in
the table.
5. If the taken value is not #$00, compare it to the KBVALUE (returned by the row-detection
algorithm) which bears the coordinate of the pressed key.
6. If the value from KBTABLE is not equal to KBVALUE, increment index by two and go back
to step 3.
7. If the condition of step 6 is false, increment the index by one and load the value pointed
by.
8. Return the value loaded of step 7.

Figure 2.1.3.- Debugging the code for PORTF initialization


Flow chart for Row-Detection Algorithm

Flow chart for Look-up table algorithm

Setup

PORTF

Start
Initialize

PORTF

Read

PORTF

Key

pressed?

no

yes

Rotate
1
bit
left

of
TMPVAR

Read

PORTF

Key

pressed?

no

yes

Return

KBVALUE

END
Start
Define

KBTABLE

Initialize

H:X
Register

Load
value
pointed

by
H:X
from
KBTABLE

BEQ

Z
=
1?

Return
#$FF

(Not
found)

END
no

yes

KBTABLE
!=

KBVALUE?

(fetched)

Increment

(H:X)
by
2

Increment

(H:X)
by
1

yes

no

Load
value

pointed
by
(H:X)

Return
#$FF

(Not
found)
END


Assembly code for Lab 3.2 Keypad and LEDs:
; Include derivative-specific definitions
INCLUDE 'derivative.inc'
;
; export symbols
;
XDEF _Startup
ABSENTRY _Startup
;
; variable/data section
;
ORG Z_RAMStart ; Insert your data definition here
TMPVAR: DS.B 1
KBVALUE: DS.B 1
;-- LOOKUP TABLE---
KBTABLE:
DC.B $7E,$00,$BE,$10,$DE,$20,$EE,$30
DC.B $7D,$40,$BD,$50,$DD,$60,$ED,$70
DC.B $7B,$80,$BB,$90,$DB,$A0,$EB,$B0
DC.B $77,$C0,$B7,$D0,$D7,$E0,$E7,$F0
DC.B $00
;
; code section
;
ORG ROMStart
_Startup:
LDHX #RAMEnd+1 ; initialize the stack pointer
TXS
MOV #$FF,PTAD
MOV #$F0,PTADD
LDA #$53 ; disable watchdog
STA SOPT
PTF_INIT: LDA #$00 ; init data port F
STA PTFD ; init data direction port F
LDA #$0F ; inputs, outputs
STA PTFDD ; COL = 0, ROW = F
LDA #$F0
STA PTFPE ; PULL-UP for columns(inputs)
mainLoop:
JSR KBA
STA KBVALUE
JSR ENCODE
; DO SOMETHING
CBEQA #$FF,display
COMA
display: STA PTAD
BRA mainLoop
;----- row scan KEY-PRESSED detection-----
; variable: KBVALUE
; entry: A


KBA:
MOV #$FE,TMPVAR ;%11111110
LDX #$04 ; scan 4 rows
KB1:
LDA PTFD ; read PORTF
ORA #$0F ; %00001111 keep columns(H), SET rows(L)
AND TMPVAR
STA PTFD ; row value obtained(L)
NOP
NOP
AND #$F0 ; %11110000 keep columns(H) CLEAR rows(L)
CBEQA #$F0,KB2 ; if not key pressed, go to KB2
LDA PTFD ; if pressed, then store the value in A
BRA KB3
KB2:
SEC ; SET CARRY BIT = 1
ROL TMPVAR ; SHIFT ZERO TO LEFT means: going through the
rows
DBNZX KB1 ; go back and check if changes the PORTFD(High)
and (Low)
LDA #$FF ; if no key pressed
KB3: RTS
;----------------------------------------------
;----- KEY SYMBOLL LOOK UP -----
; input parameter: KBVALUE
; output:A = key coded
ENCODE:
LDHX #$0000
ENC1:
LDA KBTABLE,X
BEQ ENC3 ; if Z = 1
CMP KBVALUE ; if not, compare
BNE ENC2 ; if not eq, jump to ENC2
INCX
LDA KBTABLE,X
BRA RETURN
ENC2:
INCX
INCX
BRA ENC1
ENC3:
LDA #$FF; ; FF for undefined value
RETURN:
RTS
;**************************************************************
;* spurious - Spurious Interrupt Service Routine. *
;* (unwanted interrupt) *
;**************************************************************
spurious: ; placed here so that security value
NOP ; does not change all the time.
RTI
;**************************************************************
;* Interrupt Vectors *


;**************************************************************
ORG $FFFA
DC.W spurious ;
DC.W spurious ; SWI
DC.W _Startup ; Reset

3. Keypad and 8-segment LED

Write a program that detect the pressed key and change 8-segment LED’s status by showing the
corresponding number assigned to the key.

To connect the 8-segment LED is required to use another PORT than PORTA and PORTF, so
PORTB is available.

2.1 Algorithms

Same
as
Lab3.2.
Row-‐detection
and
Look-‐up
table,
the
only
difference
is
the
KBTABLE
which
now

bears
the
code
depicted
by
Table
2.3.1.

Table 2.3.1.- Decodification from 4-bit numbers to 8-bit Display respectively.

To
implement
this
program,
is
pretty
much
the
same
as
the
last
section
just
by
replacing
the

KBTABLE
by
the
Table
2.3.1.

Number h g f e d c b a Code
0 0 0 1 1 1 1 1 1 0x3F
1 0 0 0 0 0 1 1 0 0x06
2 0 1 0 1 1 0 1 1 0x5B
3 0 1 0 0 1 1 1 1 0x4F
4 0 1 1 0 0 1 1 0 0x66
5 0 1 1 0 1 1 0 1 0x6D
6 0 1 1 1 1 1 0 1 0x7D
7 0 0 0 0 0 1 1 1 0x07
8 0 1 1 1 1 1 1 1 0x7F
9 0 1 1 0 1 1 1 1 0x6F
A 0 1 1 1 0 1 1 1 0x77
B 0 1 1 1 1 1 0 0 0x7C
C 0 1 0 1 1 0 0 0 0x58
D 0 1 0 1 1 1 1 0 0x5E
E 0 1 1 1 1 0 0 1 0x79
F 0 1 1 1 0 0 0 1 0x71


Figure 2.3.1.- By debugging the code and pressing the key corresponding to number 3 is
depicted the 0xEE in the image highlighted with red color.

Assembly code for Lab 3.3 Keypad, 8-segments Display and 4 LEDS
; Include derivative-specific definitions
INCLUDE 'derivative.inc'
;
XDEF _Startup
ABSENTRY _Startup
ORG Z_RAMStart ; Insert your data definition here
TMPVAR: DS.B 1
KBVALUE: DS.B 1
KBLEDS: DS.B 1
KB7SEG: DS.B 1
;-- LOOKUP TABLE---
KBTABLE2: ; table for 4 LEDs
DC.B $7E,$00,$BE,$10,$DE,$20,$EE,$30
DC.B $7D,$40,$BD,$50,$DD,$60,$ED,$70
DC.B $7B,$80,$BB,$90,$DB,$A0,$EB,$B0
DC.B $77,$C0,$B7,$D0,$D7,$E0,$E7,$F0
DC.B $00
KBTABLE: ; table for 8-segments LED
DC.B $7E,$3F,$BE,$06,$DE,$5B,$EE,$4F
DC.B $7D,$66,$BD,$6D,$DD,$7D,$ED,$07
DC.B $7B,$7F,$BB,$6F,$DB,$77,$EB,$7C
DC.B $77,$58,$B7,$5E,$D7,$79,$E7,$71
DC.B $00
ORG ROMStart
_Startup:
LDHX #RAMEnd+1 ; initialize the stack pointer
TXS
MOV #$FF,PTAD
MOV #$F0,PTADD
MOV #$00,PTBD
MOV #$FF,PTBDD
LDA #$53 ; disable watchdog
STA SOPT
PTF_INIT: LDA #$00 ; init data port F


STA PTFD ; init data direction port F
LDA #$0F ; inputs, outputs
STA PTFDD ; COL = 0, ROW = F
LDA #$F0
STA PTFPE ; PULL-UP for columns(inputs)
mainLoop:
JSR KBA
STA KBVALUE
JSR ENCODE
STA KB7SEG
JSR ENCODE2
STA KBLEDS
LDA KB7SEG
CBEQA #$FF,clear ; if no key pressed
STA PTBD
LDA KBLEDS
COMA
STA PTAD
BRA back
clear: MOV #$00,PTBD
MOV #$FF,PTAD
back BRA mainLoop
;----- row scan KEY-PRESSED detection-----
; variable: KBVALUE
; entry: A
KBA:
MOV #$FE,TMPVAR ;%11111110
LDX #$04 ; scan 4 rows
KB1:
ORA #$0F ; %00001111 keep columns(H), SET rows(L)
AND TMPVAR
STA PTFD ; row value obtained(L)
NOP
NOP
AND #$F0 ; %11110000 keep columns(H) CLEAR rows(L)
CBEQA #$F0,KB2 ; if not key pressed, go to KB2
LDA PTFD ; if pressed, then store the value in A
BRA KB3
KB2:
SEC ; SET CARRY BIT = 1
ROL TMPVAR ; SHIFT ZERO TO LEFT means: going through the
rows
DBNZX KB1 ; go back and check if changes the PORTFD(High)
and (Low)
LDA #$FF ; if no key pressed
KB3: RTS
;----------------------------------------------
; output:VALUE CODED FOR 8-SEGMENT LED
ENCODE:


LDHX #$0000
ENC1:
LDA KBTABLE,X
BEQ ENC3 ; if Z = 1
INCX
LDA KBTABLE,X
BRA RETURN
ENC2:
INCX
INCX
BRA ENC1
ENC3:
RETURN:
RTS
;----------------------------------------------
; output:VALUE CODED FOR 4 BITS, SO 4 LEDS
ENCODE2:
LDHX #$0000
ENC21:
LDA KBTABLE2,X
BEQ ENC23 ; if Z = 1
INCX
LDA KBTABLE2,X
BRA RETURN2
ENC22:
INCX
INCX
BRA ENC21
ENC23:
RETURN2:
RTS
;**************************************************************
;* spurious - Spurious Interrupt Service Routine. *
;* (unwanted interrupt) *
;**************************************************************
spurious: ; placed here so that security value
NOP ; does not change all the time.
RTI
;**************************************************************
;* Interrupt Vectors *
;**************************************************************
ORG $FFFA


DC.W spurious ;
DC.W spurious ; SWI
DC.W _Startup ; Reset

Results with Video attached to the e-mail:

Switch Control and Time Delay - Keypad

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