PINMODE effective for GPIO only?

Started by reich_wolfgang October 9, 2009
LPC24xx:
For GPIO port pins, does the PINMODE pull up/down setting also have effect when the pin is configured not for GPIO, but for other functions?
The manual says "The PINMODE registers control the on-chip pull-up/pull-down resistor feature for all GPIO ports."
I'm not sure if this means GPIO-accessible ports in general or only ports actually configured for GPIO function.

An Engineer's Guide to the LPC2100 Series

Hi Wolfgang,

--- In l..., "reich_wolfgang" wrote:
>
> LPC24xx:
> For GPIO port pins, does the PINMODE pull up/down setting also have effect when the pin is configured not for GPIO, but for other functions?
> The manual says "The PINMODE registers control the on-chip pull-up/pull-down resistor feature for all GPIO ports."
> I'm not sure if this means GPIO-accessible ports in general or only ports actually configured for GPIO function.
>

The PINMODE setting is independent of the PINSEL setting. The pull-ups/-downs can be used for instance when the pin is used as UART RX line.

Rolf

Hi Rolf,

> The PINMODE setting is independent of the PINSEL setting. The pull-ups/-downs can be used for instance when the pin is used as UART RX line.
>

I tested PINMODE setting on OLIMEX LPC-2478STK board.
Results as below.

PIN PINSEL PINMODE result
--------------------------------
P0.3 RXD0 pull-up -> work well
pull-down -> work well
neither pull-up nor pull-down -> work well
---------------------

why ? PINMODE is not effective ?
Please any advice.
--- In l..., "rolf_meeser" wrote:
>
> Hi Wolfgang,
>
> --- In l..., "reich_wolfgang" wrote:
> >
> > LPC24xx:
> > For GPIO port pins, does the PINMODE pull up/down setting also have effect when the pin is configured not for GPIO, but for other functions?
> > The manual says "The PINMODE registers control the on-chip pull-up/pull-down resistor feature for all GPIO ports."
> > I'm not sure if this means GPIO-accessible ports in general or only ports actually configured for GPIO function.
> > The PINMODE setting is independent of the PINSEL setting. The pull-ups/-downs can be used for instance when the pin is used as UART RX line.
>
> Rolf
>

Hello,

> I tested PINMODE setting on OLIMEX LPC-2478STK board.
> Results as below.
>
> PIN PINSEL PINMODE result
> --------------------------------
> P0.3 RXD0 pull-up -> work well
> pull-down -> work well
> neither pull-up nor pull-down -> work well
> ---------------------
>
> why ? PINMODE is not effective ?
> Please any advice.

what do you think should have happened in your test ?
What does "work well" mean ? That your communication is still working as expected ?
Have you already googled for the purpose of a pull-up or pull-down ?

Best regards,

Martin