Lpc2000

Hi,
I am newbie, working with phycore LPC2294. 

For testing purpose I have connected 8 LEDs to the P0.0-p0.7. I have 
applied right shifting algorithm. There the LED connected to P0.2 is 
on but voltage is very low. Where all the LEDs are bright, there the 
LED connected to P0.2 is dimming. I got nothing special with that port 
in the datasheet. 

Is there any problem in my board? Or anything special that I missed? 
How would I solve this problem?

Thanks in advance.

If I remeber correctly (don't have all the docs here right now), those 
are I2C pins. These pins need pullup resistors because they can only 
pull down a pin to gnd. This should also be in the datasheet or the user 
manual.

Richard.




mahbub1833 wrote:

> Hi,
> I am newbie, working with phycore LPC2294.
>
> For testing purpose I have connected 8 LEDs to the P0.0-p0.7. I have
> applied right shifting algorithm. There the LED connected to P0.2 is
> on but voltage is very low. Where all the LEDs are bright, there the
> LED connected to P0.2 is dimming. I got nothing special with that port
> in the datasheet.
>
> Is there any problem in my board? Or anything special that I missed?
> How would I solve this problem?
>
> Thanks in advance.
>

mahbub1833 wrote:

>Hi,
>I am newbie, working with phycore LPC2294. 
>
>For testing purpose I have connected 8 LEDs to the P0.0-p0.7. I have 
>applied right shifting algorithm. There the LED connected to P0.2 is 
>on but voltage is very low. Where all the LEDs are bright, there the 
>LED connected to P0.2 is dimming. I got nothing special with that port 
>in the datasheet. 
>
>Is there any problem in my board? Or anything special that I missed? 
>  
>

Probably giving us some parametric & specific information on:

* What is supply voltage on the "other" side of the LED (5v, 3.3v, 1.8v)?

* What is the typical Vf (Forward Voltage) of the LEDs?

* Are you using voltage dropping resistors in series with the LEDs?

* Are you pulling the LED cathode LOW to GND with the port pin(s), or 
driving the Anode HIGH?

* Are the LED diodes a commercial part (similar candella), or are they 
"grab bag" surplus LEDs?


Regards,

TomW


-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
----------------------------------------------------

Yes, P0.2 and P0.3 are I2C pins. But my question is when I enable the 
pins as GPIO (in IAR by PINSEL0_bit.P0_2 = 0x00; and PINSEL0_bit.P0_0 
= 0x00 ;), then the supply voltage should change to 5v. Isn't it?

Doesn't the voltage change with the change in behavior?
 
Thanks a lot.

--- In lpc2000@yahoogroups.com, Richard Duits <yahoo@r...> wrote:
>
> If I remeber correctly (don't have all the docs here right now), 
those 
> are I2C pins. These pins need pullup resistors because they can only 
> pull down a pin to gnd. This should also be in the datasheet or the 
user 
> manual.
> 
> Richard.
> 
> 
> 
> 
> mahbub1833 wrote:
> 
> > Hi,
> > I am newbie, working with phycore LPC2294.
> >
> > For testing purpose I have connected 8 LEDs to the P0.0-p0.7. I 
have
> > applied right shifting algorithm. There the LED connected to P0.2 
is
> > on but voltage is very low. Where all the LEDs are bright, there 
the
> > LED connected to P0.2 is dimming. I got nothing special with that 
port
> > in the datasheet.
> >
> > Is there any problem in my board? Or anything special that I 
missed?

> > How would I solve this problem?
> >
> > Thanks in advance.
> >
>

These pins do not have any source transistors, they are strictly 
open-drain output or an input. Changing P0.2 & P0.3 to GPIO will not 
connect source transistors as they do not exist. As has been said many 
times ... RT*M.

BTW, drive the leds by sinking current rather than trying to source. If 
you do this you also have the option of tying the leds to a +5V supply 
(through resistors of course) if that is more convenient.

*Peter*

mahbub1833 wrote:

> Yes, P0.2 and P0.3 are I2C pins. But my question is when I enable the 
> pins as GPIO (in IAR by PINSEL0_bit.P0_2 = 0x00; and PINSEL0_bit.P0_0 
> = 0x00 ;), then the supply voltage should change to 5v. Isn't it?
>
> Doesn't the voltage change with the change in behavior?