Digital touch Screen Combination lock

[astanapane]

im still in lesson 1.



i need to completely understand it with the use of the port schmeatic.

[richard]

make lesson 1 loop like this and try with and without the nop

loopy:
lata=2
pause 10
porta.1 = 0
;@ nop
porta.0 = 1




pause 1000
 
goto loopy

the secret is that leds when forward biased charge up , when you set them low the charge can hold the pin high long enough
to trigger a rmw event on a fast chip. the nop allows enough time for the charge to dissipate {62 nano seconds}

[astanapane]

one by one,

i'm doing some test. Really i have my own way to catch up and understand things.

first of all for lata we can only write up to 255 as it is 8 bit.

I'm still figuring out step by step the diagram.

[astanapane]

this is really helpful for me as well.

https://download.mikroe.com/document...c/help/rmw.htm

[astanapane]

ok i think i have some how understood the concept.

my question is.

How could we assign a value that can be stored in memory and represent the state of the pin itself. (0 or 1)

but at the same time to not read the actual pin, but the value that is stored in memory.

[richard]

How could we assign a value that can be stored in memory and represent the state of the pin itself. (0 or 1)


but at the same time to not read the actual pin, but the value that is stored in memory.

simple, to read the value assigned to pins designated as output read latx its value is always what you last set it to
the latx value of pins set as input is meaningless in regards to actual pin logic level

to read the actual pin logic levels at a point in time read portx , its always the actual pin value at read time

pin and latx values are not necessarily equal at a point in time, pins set as output are subject to real world physical constraints dictated by the load impedance they are driving

[astanapane]

i did a small test but it is not what i need.

I would like now once again to clear the following.

Henrik said

"One more thing: You're clearly reading PORTB which must mean you're using those five low bits as inputs, yet, at the top of the program you have TRISB = %00000000 which makes all of PORTB outputs..."

As this statement, how could we read the status of the actual pin without using the port as input. Could you please explain to me the method?

ANSELA = 0
    DEFINE OSC 64 
    OSCCON = $70
    OSCTUNE.6 = 1
    TRISA = %11111100 
                             
led1 var porta.0    ; alias led1 to porta.0
led2 var porta.1    ; alias led2 to porta.1
x    var bit            ; tried to use X var as a bit in order to hold the value of the actual status of the pin.

lata = 0               ; based on the schematic, we write to LATA and clear the ports 

x = 0                  ; we write 0 to var X


loopy:
lata.0 = 1           ; we write 1 to lata.0
gosub holdmem  ; gosub to holdmem

pause 500
read 5,led2        ; write the value of the location 5 to led2

pause 500
lata.0 = x          ; write the value of X to lata.0
lata.1 = x          ; write the value of X to lala.1

pause 1000
goto loopy

holdmem:
write 5,led1  ; read the state of the porta.0 and place it to location 5 in memory.
return