Forum Need help with the following Homework assignment… Design a fire alarm system using a 8051 microcontroller. The specs are as follows: A) If the alarm is detected (one of the switches is activated) it should start flashing 4 LEDS (4 on the right (LEDS 1-4) and 4 on the left (LEDS 5-8), alternating). B) If the alarm is not detected, the display should show only 2 middle LEDS (LEDS 4 & 5) steadily ON (not flashing) indicating NORMAL operation. This is the code I’ve come up with so far, but I appear to be stuck. I would appreciate and assistance. Thank you.
Code…
ORG 0H ;Program starting location MOV A, #0 ; MOV P2, A ; MOV A, #OFFH ; MOV P1, A ;
INPUT: MOV A, P1 ;
HERE: JNB A, HERE ; MOV P2, #1 ;
DELAY: MOV R3, #15 ; OUTER: MOV R2, #240 ; INNER: DJNZ R2, INNER ; DJNZ R3, OUTER ; RET
SDELAY: MOV R5, #45 ;put 45 in R5 H3: MOV R4, #242 ;put 242 in R4 H2: MOV R3, #255 ;put 255 in R5 H1: DJNZ R3, H1 ;Decrement R3 keep @ H1 if not zeroed DJNZ R4, H2 ;Decrement R4 keep @ H2 if not zeroed DJNZ R5, H3 ;Decrement R5 keep @ H3 if not zeroed RET ;Return & Go back to line after ACALL
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Magic numbers are certainly something to be avoided, but manifests are definitely not always the best solution.
Many is the time I've seen someone write something like mov uart_ctrl, UART_ENABLE_TX .Code looks fine, people say it's self commenting. But then it's wrong. Nothing is there to say that it should be an or operation rather than a mov.
index = CHARACTER_LOOP_COUNT
Fine if you only happen to have one requirement for such a value in a module. Not so good if there are a number of them there. Too easy to devise clever names as:
#define CHARACTER_LOOP_COUNT1 10 #define CHARACTER_LOOP_COUNT2 107 #define CHARACTER_LOOP_COUNT3 19 #define CHARACTER_LOOP_COUNT4 33 #define CHARACTER_LOOP_COUNT5 27
I'm wary of people who insist on tight rules. We have recently had [another] new development lead. He insists that we all train up and learn his current best practices. Trouble is, his code always seems to fail. Of course, it's never his current best practices that are anything to do with it and he would rather blame all other code that doesn't follow his practices. So far, his fail score is way higher than mine!
The only absolute rule is that there can be no absolute rule - an inflexible tree snaps in the storm.
But the general idea is to know and understand rules before starting to bend them. It's much better to cherry-pick what works well than spending the day trying to hammer down a square peg in a round hole.
should be something like #define FETCH_CHARACTER_LOOP_COUNT 10 #define IMAGE_CHARACTER_LOOP_COUNT 107 #define RESPONSE_CHARACTER_LOOP_COUNT 19 #define COMPARE_CHARACTER_LOOP_COUNT 33 #define DISPLAY_CHARACTER_LOOP_COUNT 27
your version STILL uses "magic numbers"
oh yes, I have seen this "workaround": typedef enum {ONE, TWO, THREE, FOUR}
the idea is that you dismiss those that play games like this