Connecting a button to PICAXE 20X2

[Sean87]

Hi all,

How can I connect a micro button to 20X2 as an input? The button has 4 legs and I have a regulated 3V as supply to the chip and some LED's.

Thanks.

 

[MartinM57]

Your button is just like a switch, so see the interfacing techniques in Manual 3.

You need to check which contacts close when the switch is pressed with a multimeter...

 

[Sean87]

Your button is just like a switch, so see the interfacing techniques in Manual 3.

You need to check which contacts close when the switch is pressed with a multimeter...

OK I found the proper pins of the switch.

Now some questions.

1- What is the maximum voltage I can use for an input?
2- the following code does not compail (I am trying to check if c.6 is high then turn on some LED's)

if c.6 = high then 
high 0,1,2,3,4,5,6,7
endif

 

[nick12ab]

1- What is the maximum voltage I can use for an input?
2- the following code does not compail (I am trying to check if c.6 is high then turn on some LED's)

if c.6 = high then 
high 0,1,2,3,4,5,6,7
endif

Maximum input voltage is around Vdd + 0.3v so 3.6v at a 3.3v supply.

Replace 'if c.6 = high' with 'if pinC.6 = 1' as 'high' is a command and can't be used in an expression.

Also, since you're changing all pins on port B with the 'high' command, it may be better to use 'pinsB = 255' instead.

ADDED: Since you're using a pin which supports internal pullups, you can wire the switch like this and save on a resistor:

You will need to use this at the beginning:

pullup 2

and exchange any 'if pinC.6 = 1' with 'if pinC.6 = 0' and vice versa.

 

[eclectic]

1. The supply voltage. (to be safe)

2.

if pinC.6 = 1 then ; ******

high 0,1,2,3,4,5,6,7

;or
; OutpinsB = %11111111  ; perhaps?
endif

 

[Sean87]

1. The supply voltage. (to be safe)

2.

if pinC.6 = 1 then ; ******

high 0,1,2,3,4,5,6,7

;or
; OutpinsB = %11111111  ; perhaps?
endif

Thanks.

I am a bit confused. How can I do something that when I hold the button the LED be on and when I release it they turn off?

 

[Jamster]

In a loop keep testing the state of the buttons:

do
if pinc.6=1 then
high 0,1,2,3,4,5,6,7
else
low 0,1,2,3,4,5,6,7
endif
loop

 

[nick12ab]

I am a bit confused. How can I do something that when I hold the button the LED be on and when I release it they turn off?

Simply have:

if pinC.6 = 1 then
   pinsB = 255
else
   pinsB = 0
end if

 

[eclectic]

And, Manual 3, p. 27
Switch bounce

 

[nick12ab]

And, Manual 3, p. 27
Switch bounce

Probably won't have any effect on the rather slow PICAXE unless it's running at top speed or with poor quality switches, in which case a simple 'pause 20' will do.

 

[Sean87]

ADDED: Since you're using a pin which supports internal pullups, you can wire the switch like this and save on a resistor:

You will need to use this at the beginning:

pullup 2

and exchange any 'if pinC.6 = 1' with 'if pinC.6 = 0' and vice versa.

Thanks, this pullup was super helpful!

 

[Sean87]

In a loop keep testing the state of the buttons:

do
if pinc.6=1 then
high 0,1,2,3,4,5,6,7
else
low 0,1,2,3,4,5,6,7
endif
loop

Thanks this works also.

But question is that checking for button states always are linear for picaxe? I mean it just follows top to bottom of the program? What if the program is in another loop which does not have anything to do with inputs and in the middle user pushes a button which requires a urgent part of code to be ran. Is there somehing like EVENTS ?

 

[MPep]

No. You would need to check for the state of the button in youor subroutines.

 

[westaust55]

Yes, the EVENTS you mention are called INTERRUPTS.

See the SETINT command in PICAXE manual 2(currently V7.7) page 215