Input Question

staffshome

Hello all,

use code below in my program.

IF modein = 1 THEN····························· 'latched switch, resets to 1 on power up
GOSUB Economy
ELSE
GOSUB Sport
ENDIF

I look at this input repeatedly & only want action on change of state,is there a way to do this.
thought maybe get scratchpad byte & current status but not sure how to do it

regards Adrian

·

Tracy Allen

Use a one-bit internal variables to store the state. That allows the program to look for a change:

modein  PIN 0       ' alias for the input pin
modein0 VAR BIT   ' state variables for current and prior state
modein1 VAR BIT

modein1 = modein  ' initialize prior state
DO
   modein0 = modein   ' read the pin
   IF modein1 ^ modein0 & modein1  THEN                              ' =1 iff pin changes low to high
      GOSUB Economy
      ELSE
      GOSUB Sport
   ENDIF
   modein1 = modein0    ' update the prior state
LOOP

Economy:  DEBUG "1" : RETURN
Sport: DEBUG "0" : RETURN

The logic statements involving XOR=^ and AND=& detect the change of state.

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Tracy Allen
www.emesystems.com

staffshome

Hi Tracy,

Thanks for your reply,will giveit a go in my prog

Regards Adrian

staffshome

Hi Tracy,

tried your code & appears to work same as my original ??.

I could be i didn't explain what i need correctly.

my program runs the code shown as part of a main loop & each time it loops back if for example:·modein =1

it runs the sub routine if the next time loop runs if modein unchanged sub runs again (each sub drives·same digi-pot·with with different ramping rates so if sub repeats endlessly the solenoid driven from the pot cycles & this is showing up as a pressure pulse in solenoid hydraulic circuit. So really need sub not to run again until modein changes state.

How that is a bit clearer.

regards Adrian

Tracy Allen

Be sure the initialization statement,
modein1 = modein ' initialize prior state
is NOT part of your main loop. On the other hand the update statement,
modein1 = modein0 ' update the prior state
does have to be in your main loop.


The logic function can be chosen to do what you want:

modein1 ^ modein0  ' detect transition either high to low or low to high
or
modein1 ^ modein0 & modein1  ' detect transition high to low
or
modein1 ^ modein0 & modein0  ' detect transition low to high

If you stilll have trouble with it, post your distilled code.

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Tracy Allen
www.emesystems.com