Alright thanks Olin! That cleared it up so much

I should probably take a refresher on the electronics
- Xiao Xu


On Mon, May 31, 2010 at 7:10 PM, Oli Glaser <oli.glaser@talktalk.net> wrote:

>
> ----- Original Message -----
> From: "Xiao Xu" <xiaoxu193@gmail.com>
> To: "Microcontroller discussion list - Public." <piclist@mit.edu>
> Sent: Monday, May 31, 2010 10:05 PM
> Subject: Re: [PIC]In C, how do you set a pin to high voltage?
>
>
> >I got one LED to flash on the PICkit. Thanks for the help everyone!
> >
> > I have another question though. Below is a link of schematic for the LEDs
> > on
> > the PICkit (page 2 of link below), does anyone know what combination of
> > bits
> > are required for each LED?
> >
> > For example, if I set PORTA = 0b00010000, D0 LED lights up. If I set
> PORTA
> > =
> > 0b00100000, D1 LED lights up.
> > How can I figure out what combination of high/low/no voltages are
> required
> > to light up each of the other LEDs?
> > thanks.
>
> Glad you got it sorted.
> Better schematic for Pickit 1 here:
> http://ww1.microchip.com/downloads/en/DeviceDoc/40051D.pdf
> With the settings for lighting each of the LEDs, couple of examples to get
> you going (don't want to spoil the fun of working it out totally :-).
> Basically you have to make sure that there is a channel for current through
> ONLY the LED you want to light. You can do this by setting all the pins
> that
> are not used to inputs, making then high resistance and unable to sink
> (hardly) any current. I think the examples below *should* work..
>
> So if you wanted to light D2, you would set:
> TRISA4 = 0;    // Output for high
> TRISA5 = 1;    // Make RA5 high resistance so no current can flow into it,
> stopping D0 from lighting too
> TRISA2 = 0;    // 0V (Current sink for D2)
> TRISA1 = 1;    // Make RA1 high resistance
>  PORTA = 0b00010000;    // Set RA4 to high, lighting D2 - set all bits at
> once to avoid read modify write problems
>
> To light D0, you would set:
> TRISA4 = 0;    // Output for high
> TRISA5 = 0;    // 0V (Current sink for D0)
> TRISA2 = 1;    // Make RA2 high resistance
> TRISA1 = 1;    // Make RA1 high resistance
>  PORTA = 0b00010000;    // Set RA4 high, lighting D0 this time, as current
> now has channel to ground through RA5
>
> Better way, less instructions (does same as above):
>
> for D2:
> TRISA = 0b11101011;    // Set RA4 and 2 outputs, rest high resistance
> inputs
>  PORTA = 0b00010000;    // Set RA4 to high, lighting D2 - set all bits at
> once to avoid read modify write problems
>
>  for D0:
> TRISA = 0b11001111;    // Set RA4 and 5 as outputs, rest as high resistance
> inputs
>  PORTA = 0b00010000;    // Set RA4 high, lighting D0 this time, as current
> now has channel to ground through RA5
>
> So the idea is to set the LEDs anode and cathode pins as outputs, and all
> the rest (not involved) as inputs, using the TRISA register. Then set
> *only*
> the LED anode high using PORTA. Hope I've got it right :-)
>
>
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