Syntax
Pn ( expression ) '
where n is 0 through 4
Description
Px allows you to read or write
individual pins using the NXP assigned port and
pin number. When Pn (expression) is read, the logic state of the pin corresponding to
expression is returned.
When assigning a value to Pn(expression), then pin expression is set to that value if that pin has been
assigned to be an output by writing to FIOxDIR.
When read Pn(x) returns a 0 or -1. Why -1 and
0? The main reason is that operations of operators like NOT are assumed to
be bitwise until there is a Boolean operation in the expression, and NOT 0 is
equal to -1. When setting a pin state with Pn(x) = 0 then the pin becomes
low, any other value and the pin becomes high, so Pn(x) =1 and Pn(x) = -1 both
set the pin high.
These pin numbers correspond to the port pin assignments
from NXP.
This feature is part of the compiler and requires
version 8.04c or later. It has not been added to the on-chip compiler of
the ARMweb.
Example
On the SuperPRO and PROplus:
#define
FIO1DIR
*&H2009C020
' or use
#include <LPC17xx.bas>
' Set pin 9 as an output and drive it high
FIO1DIR =
FIO1DIR
or (1<<9)
P1(9) = 1
P1(9) = NOT (P1(9) and (1 <<9)) ' invert pin P1.9 -- works as
you can always
read the
state of a pin
' read value of P1.8
x =
P1(8)
'
change bit 9 back to
an
input
FIO1DIR = FIO1DIR and
NOT(1<<9)
On the ARMweb or DINkit:
#define
FIO1DIR
*&H3FFFC020
' or use
#include <LPC21xx.bas>
#define
SCB_SCS *&HE01FC1A0
SCB_SCS =
3 ' required
to
enable port1 for
firmware before 7.47
' Set pin 9 as an output and drive it high
FIO1DIR =
FIO1DIR
or (1<<9)
P1(9) = 1
P1(9) = NOT (P1(9) and (1 <<9)) ' invert pin P1.9 -- works as
you can always
read the
state of a pin
' read value of P1.8
x =
P1(8)
'
change bit 9 back to
an
input
FIO1DIR = FIO1DIR and NOT(1<<9)
Or you can also define a macro, keeping with the IN/OUT
BASIC style
#include <LPC17xx.bas>
#define OUTPUT0(pin) FIO0DIR =
FIO0DIR or
(1
<< pin)
#define INPUT0 (pin)
FIO0DIR = FIO0DIR and not(1 << pin)
#define
OUTPUT1(pin) FIO1DIR =
FIO1DIR or
(1
<< pin)
#define INPUT1 (pin) FIO1DIR = FIO1DIR
and not(1 << pin)
#define OUTPUT2(pin)
FIO2DIR =
FIO2DIR or
(1
<< pin)
#define INPUT2
(pin) FIO2DIR = FIO2DIR and not(1 << pin)
#define OUTPUT4(pin) FIO4DIR =
FIO4DIR or
(1
<< pin)
#define INPUT4 (pin)
FIO4DIR = FIO4DIR and not(1 << pin)
OUTPUT2(10)
while 1
x=x+1
P2(10) = x and
1 ' blinky for the
SuperPRO and PROplus
wait(500)
loop
Differences from other BASICs
- no equivalent in Visual BASIC
- no equivalent in PBASIC
See
also
