Lpc2000

---- Original Message ----
From: "rtstofer" <rstofer@...>
To: <lpc2000@yahoogroups.com>
Sent: Wednesday, May 31, 2006 3:24 PM
Subject: [lpc2000] Re: PINSEL Queries

> --- In lpc2000@yahoogroups.com, "suyash" <suyash_shembekar@...> wrote:
>>
>> I am using ARM LPC2106, I have following doubts about the
>> configuration of PINSEL0 and PINSEL1.
>>
>> 1)where exactly should I define it in the initialsation?
>>  In common system initialisation or at the eac and every periphral
>> (ex. UART0 or SPI etc.) initialisation.
>
> It's your choice!  I do most of the initialization in just one place
> in a function I call from main().  But, I don't think I like this
> approach.  Next time I will set the USART pins in an initialization
> routine in the serial IO file.  Same for SPI, I2C, etc.

Writing some big magical values to PIN->SEL0 and PIN->SEL1 in the beginning
of main() is possible but not very service friendly imho.

Instead I set both PIN->SELx to 0 in main() and let the various subsystems
modify "their" bits.  I have a #define for each pin, and a macro for setting
PIN->SELx bits.  The SET_PINSEL_P0() macro changes the pin function from 0
to 1, 2 or 3 by ORing the appropriate bits to the appropriate PIN->SELx
register.

#define P0_TXD0    (1u<<0)
#define P0_RXD0    (1u<<1)
#define P0_OUT4    (1u<<4)
#define P0_PWM    (1u<<7)
...

#define SET_PINSEL_P0(p0bit,func)  (((p0bit) <= 0x00008000) ?  \
 (PIN->SEL0 |= (p0bit)*(p0bit)*(func)) :       \
 (PIN->SEL1 |= ((p0bit)>>16) * ((p0bit)>>16) * (func)))

Then in each subsystem I can configure the pins like this:

void UartInit (void)
{
  SET_PINSEL_P0 (P0_TXD0, 1);    /* TxD0, not GPIO */
  SET_PINSEL_P0 (P0_RXD0, 1);    /* RxD0, not GPIO */
  ...
}

void PwmInit (void)
{
  SET_PINSEL_P0 (P0_PWM, 2);    /* PWM2, not GPIO */
  ...
}

void OutputInit (void)
{
  IO->DIR0 |= P0_OUT4;    /* GPIO out, not GPIO in */
  IO->SET0 = P0_OUT4;    /* Initially high, not low */
  ...
}


Karl Olsen