I'm posting this here because it may be more of an electronics issue.
Anyways, I have a program which calls the dkey function to try to get a value based on the key pressed. I have three keys. Two are tied to their own GPIO pins and the third key functions exactly the same as the other two pressed at the same time.
When I press any of the first two keys (tied to its own GPIO pin), this function works fine, but sometimes when I use the third key, it tries to function as if its the first key but I don't understand why.
I set the timer function to execute about every 4096 clock cycles (about 2ms). I put it in timer mode 1 with TH0 as #0E0h and TL0 as #0h.
With my code, I deliberately use a 2ms+ delay along with a shift register approach (for a 16ms+ delay) before a button can be recognized as valid.
The keys in question I'm using are omron B3F-4000.
The diodes I'm using to connect the third key to the first two are 1N914's.
Is my hardware or timing at fault or is it something else?
Anyways, I have a program which calls the dkey function to try to get a value based on the key pressed. I have three keys. Two are tied to their own GPIO pins and the third key functions exactly the same as the other two pressed at the same time.
When I press any of the first two keys (tied to its own GPIO pin), this function works fine, but sometimes when I use the third key, it tries to function as if its the first key but I don't understand why.
I set the timer function to execute about every 4096 clock cycles (about 2ms). I put it in timer mode 1 with TH0 as #0E0h and TL0 as #0h.
With my code, I deliberately use a 2ms+ delay along with a shift register approach (for a 16ms+ delay) before a button can be recognized as valid.
The keys in question I'm using are omron B3F-4000.
The diodes I'm using to connect the third key to the first two are 1N914's.
Is my hardware or timing at fault or is it something else?
Code:
;Keys are hooked up as:
;Button 1 to P1.1
;Button 3 to P1.3
;Button 2 to P1.1 AND P1.3 (via diodes)
ALLKEYS equ P1
KEYCAP equ 2Ch ;keys captured
KEY1 bit KEYCAP.1
KEY2 bit KEYCAP.3
KEYS equ 2Eh ;Keys detected after scan
KEY1DOWN bit KEYS.0
KEY1HELD bit KEYS.1
KEY1UP bit KEYS.2
KEY2DOWN bit KEYS.4
KEY2HELD bit KEYS.5
KEY2UP bit KEYS.6
;Our key data so timer can process new key info while we work
;with the old
IKEY1DOWN bit ACC.0
IKEY1HELD bit ACC.1
IKEY1UP bit ACC.2
IKEY2DOWN bit ACC.4
IKEY2HELD bit ACC.5
IKEY2UP bit ACC.6
;Mask value to indicate both keys are held
;This equals IKEY1HELD and IKEY2HELD
BOTHHELD equ 22h
timer:
mov KEYCAP,ALLKEYS ;capture a new set of keys so we know what key1 and key 2 equal
reti
;here key info is obtained
getkey:
;Load first key
mov C,KEY1
mov A,UKEY1
;and put it into an 8-bit shift register named UKEY1
;this register changes value almost everytime we ask for a key
rlc A
mov UKEY1,A
;If register value=0 then key is held down (held for at least 8 key info requests)
;since press connects port pin to ground
jnz nokeyp1h
setb KEY1HELD
nokeyp1h:
;Set key down since key is held for at least 4 key info requests
cjne A,#0F0h,nokeyp1
setb KEY1DOWN
nokeyp1:
;Set key up since key is let go for at least 4 key info requests
cjne A,#00Fh,nokeyp1b
clr KEY1HELD
setb KEY1UP
nokeyp1b:
;The following is a repeat but for the other port pin connected to the keys.
mov C,KEY2
mov A,UKEY2
rlc A
mov UKEY2,A
jnz nokeyp2h
setb KEY2HELD
nokeyp2h:
cjne A,#0F0h,nokeyp2
setb KEY2DOWN
nokeyp2:
cjne A,#00Fh,nokeyp2b
clr KEY2HELD
setb KEY2UP
nokeyp2b:
;Load keys to accumulator so we can deal with them then reset keys value
mov A,KEYS
mov KEYS,#0h
clr C
ret
;Function is called in main program to get a button press. Stall if nothing is pressed
dkey:
acall getkey ;get key info
mov B,A ;save key value
anl A,#BOTHHELD ;check to see if both keys are held down
cjne A,#BOTHHELD,o3
mov A,#08h ;it is so return 8
ret
o3:
mov A,B ;restore key value
jnb IKEY1HELD,o1
clr A ;Key one held down
ret
o1:
jnb IKEY2HELD,o2
mov A,#04h ;Key 2 held down
ret
o2:
;At this point, nothing is held down so rerun the loop
sjmp dkey
