Sharing Switch and LED on one pin.

tonyp12 · 2013-01-14 19:26

The button is not pressed very often and if the light comes on by itself when button is pressed is OK.

If just using the single 230ohm (led) resistor and no 10k pull-up/down for the switch is a bonus point.

If in very short intervals turning the pin to a input to read the switch and that will turn off the LED is OK.
But if holding down switch will not turn off or on the LED is extra bonus points.

kwinn · 2013-01-14 19:37

I am assuming this is for a prop at 3.3V but confirmation would be nice. Led color (forward voltage) is also an important factor in the design.

tonyp12 · 2013-01-14 19:58

yes Prop is 3.3v, if forward voltage is determing the design I will get red, green or blue.(2v to 3v FV)

kwinn · 2013-01-14 20:46

I can come up with 4 ways to connect the led, resistor, and pb switch to the prop I/O pin to allow the state of the switch to be read but all of them cause the led to turn on or off when the switch is pressed.

Circuitsoft · 2013-01-14 21:31

{{
      &#61463;             &#61463;
      &#9492;&#61606;&#61608;&#9488;          &#9474;
         &#61628; 100     &#61567;&#61467;
  PIN &#61609;&#9472;&#9472;&#9547;&#9472;&#9472;&#9472;&#9472;&#9472;&#9472;&#9472;&#61629;&#61630;&#9472;&#9496;
         &#61628; 1M    10K
         &#61464;
}}

CON
  PIN = 4
  
PUB Test
  DIRA[PIN]~~

  repeat
    waitcnt(cnt+CLKFREQ/50)
    DIRA[PIN]~
    waitcnt(cnt+CLKFREQ/1000) ' Give the I/O some time to settle since turning off the output
    OUTA[PIN] := !INA[PIN]
    DIRA~~

This circuit will pull the I/O pin to a logic low, but won't draw enough current to light the LED. If the pin is pulled low by software, it will light the LED. Pressing the button will turn it into a pull-up, but the LED will still be lit by pulling it down.

Sharing Switch and LED on one pin.

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