Forums

LPC2114/2124 pin select usage

Started by bobtransformer March 31, 2005


I have been excited about trying the LPC2114 and LPC2124 parts (and
similar parts) and notice in the users manual that when certain pins
are assigned certain functions, other pins cannot be used for general
IO etc.

I am used to Microchip and AVR type parts where any pin can pretty
much be assigned to be used as general IO or the alternate dedicated
pin functions (TXD, RXD, PWM, cap, int, etc.)

Is it really true that these parts have this limited pin usage ?
For instance, it looks like I cannot use UART0 and UART1 and still
use PWM outputs 2 and 5 even though neither function shares pins.

I also see a lot of "reserved" pins when certain pin functions are
assigned that would waste otherwise useful IO. This would severely
limit usage of these parts.

This can't be true, can it ?
thanks,
bob


An Engineer's Guide to the LPC2100 Series


Hi Bob,

as a general rule, what is not assigned to an alternate function will
still be general purpose I/O.

In fact , you have more I/O pins on this device as compared to e.g.
the Atmel SAM7 because that device has more dedicated pins such as
debug pins and analog inputs. Overall, I like the flexiibility of the
LPC2000 series better.

hth Bob

--- In lpc2000@lpc2..., "bobtransformer" <bgudgel@e...> wrote:
>
>
> I have been excited about trying the LPC2114 and LPC2124 parts (and
> similar parts) and notice in the users manual that when certain pins
> are assigned certain functions, other pins cannot be used for general
> IO etc.
>
> I am used to Microchip and AVR type parts where any pin can pretty
> much be assigned to be used as general IO or the alternate dedicated
> pin functions (TXD, RXD, PWM, cap, int, etc.)
>
> Is it really true that these parts have this limited pin usage ?
> For instance, it looks like I cannot use UART0 and UART1 and still
> use PWM outputs 2 and 5 even though neither function shares pins.
>
> I also see a lot of "reserved" pins when certain pin functions are
> assigned that would waste otherwise useful IO. This would severely
> limit usage of these parts.
>
> This can't be true, can it ?
> thanks,
> bob





Thank you, I feel somewhat better hearing this.
What bothered me is looking at PINSEL0 and PINSEL1
registers.

When the bits are set to 00, I see pins are pretty much
GPIO (left hand column of the table). Can the pins be configured as
GPIO and then initializing the other functions such as PWM and UARTs
and A/D channls to enabled make the IO and alternate functions
available on their respective pins, while keeping the other
GPIO pins, GPIO ??

OR, how is this done ? Maybe I just need to spend a lot more
time with the manual.

Thanks,
boB
************************************************
>>>>>>>>>
Hi Bob,

as a general rule, what is not assigned to an alternate function will
still be general purpose I/O.

In fact , you have more I/O pins on this device as compared to e.g.
the Atmel SAM7 because that device has more dedicated pins such as
debug pins and analog inputs. Overall, I like the flexiibility of the
LPC2000 series better.

hth Bob


At 05:05 PM 3/31/05 +0000, bobtransformer wrote:
>Thank you, I feel somewhat better hearing this.
>What bothered me is looking at PINSEL0 and PINSEL1
>registers.
>
>When the bits are set to 00, I see pins are pretty much
>GPIO (left hand column of the table). Can the pins be configured as
>GPIO and then initializing the other functions such as PWM and UARTs
>and A/D channls to enabled make the IO and alternate functions
>available on their respective pins, while keeping the other
>GPIO pins, GPIO ??
>
>OR, how is this done ? Maybe I just need to spend a lot more
>time with the manual.

There are two bits to set the function for each pin. You just set the
appropriate PINSEL register as needed to get the combination you want.

IE

PINSEL0 = 0x40;

Sets pin 3 to function 1 and all of pins 0-2, 4-15 to 0;

You do have to set up the appropriate alternate functions as well of course.

Robert

" 'Freedom' has no meaning of itself. There are always restrictions, be
they legal, genetic, or physical. If you don't believe me, try to chew a
radio signal. " -- Kelvin Throop, III
http://www.aeolusdevelopment.com/