Pin class to allow access to single pins. More...

#include <pin.h>

Public Member Functions
	Pin ()
	Create a null pin (pin with no effect). More...

	Pin (int pin)
	Create the pin instance. More...

int	getPin (void)
	Get the pin number [0..31]. More...

void	high (void)
	Set pin to output high. More...

void	low (void)
	Set pin to output low. More...

void	toggle (void)
	Toggle the pin on output. More...

int	input (void)
	Set the pin to input and get it's value. More...

void	output (int setting)
	Output a value on the pin. More...

bool	isOutput (void)
	Get the input or output direction. More...

void	pwm (const int decihz, const bool useCTRA=true, Pin *alternatePin=NULL)
	Output a PWM wave on a pin. More...

Detailed Description

Pin class to allow access to single pins.

What's with the attribute((always_inline))? SRLM found that the forced inlining is essential to performance. Without it GCC would not inline a function (even if marked) if it was used more than two or three times. This has a rather drastic performance impact. It does come at the expense of some space, however. For example, the high() function expands to 5 instructions:

mov r7, OUTA
rdlong  r6, r3
or  r7, r6
mov OUTA, r7
or  DIRA,r6

If you use high() in many places the total could add up. On the other hand, the forced inlining may give the optimizer more chances to make things small. You should try it both ways and compare.

Hardware: To read 3.3v signals just connect the signal directly to any I/O pin. To read a 5v signal connect it to any I/O pin through a 3.3kOhm (or higher) resistor. To read a higher voltage, use the following equation to determine the proper series voltage: resistance = (voltage - 3.3v - 0.6v) / 500uA

The original source for this class was posted by David Michael Betz, and modified by SRLM.

Constructor & Destructor Documentation

INLINE Pin::Pin ( )

Create a null pin (pin with no effect).

INLINE Pin::Pin ( int pin)

Create the pin instance.

Parameters

pin	the I/O pin number (0 through 31) to control.

Member Function Documentation

INLINE int Pin::getPin ( void )

Get the pin number [0..31].

Returns -1 if no pin.

INLINE void Pin::high ( void )

Set pin to output high.

INLINE int Pin::input ( void )

Set the pin to input and get it's value.

Returns: 1 if the pin is high, 0 if it is low.

INLINE bool Pin::isOutput ( void )

Get the input or output direction.

Warning: Can only tell if the output bit is set for this cog (not all cogs)

Returns: true if output, false if input

INLINE void Pin::low ( void )

Set pin to output low.

INLINE void Pin::output ( int setting)

Output a value on the pin.

Parameters

setting 1 to output high, 0 to output low.

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void Pin::pwm	(	const int	decihz,
		const bool	useCTRA = `true`,
		Pin *	alternatePin = `NULL`
	)

inline

Output a PWM wave on a pin.

Warning: You MUST stop the PWM by calling this function with a frequency of 0!. Otherwise the Propeller counters will continue to output the PWM, even if this class has been garbage collected and destroyed.; This function uses the Propeller counters. There are only two per cog, so that means that you can have up to two PWM waves and that's it! In addition, nothing else can use the counters.

Parameters

decihz	The frequency to PWM at. A parameter of 0 disables the PWM.
useCTRA	Explicitly specify which counter to use. True for CTRA, false for CTRB
alternatePin	Specify a pin to have an alternating PWM on. That pin will be the logical inverse of whatever this pin is.

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Public Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation