Assign a mnemonic name to PORT.PIN

Hi Leonardo,

Simply using

#define MYPIN GPIO_PORT_P3

Should do. I usualy also do since the base normally is necessary (i use TivaWare which the API is about the same)

#define MYPIN_Periph SYSCTL_PERIPH_GPIOF

#definy MYPIN_Base GPIO_PORTF_BASE

This are names for the Tiva, i don't know MSPWare names.

Thank you Luis,

But I would a unique mnemonic for port + pin..

Thanks

Individual bits are not addressable, so you can’t define a symbol for a pin in a way you can do x=1 then.
You can define a bitfield, and then a symbol for an element in a bitfield, but bitfields are inefficient if used on hardware registers (the compiler cannot do optimizations then).
Also, the bit order in bitfields is not specified by the C language, so using them may be not portable.

What you can do is to create symbols that perform a complete operation.

#define MYPIN_SET() GPIO_PORT_P3|=GPIO_PIN0
#define MYPIN_CLEAR() GPIO_PORT_P3&=~GPIO_PIN0

Jens-Michael,

Good information.

The Driverlib API that OP is using is verbose in terms of the amount of typing required if you use the predefined macro constants.

Example:

//*****************************************************************************
//
// Prototypes for the APIs.
//
//*****************************************************************************
extern void GPIO_setAsOutputPin(uint8_t selectedPort,
                                uint16_t selectedPins);

and the macros are defined like:

#define GPIO_PORT_P1                                                          1
#define GPIO_PORT_P2                                                          2
#define GPIO_PORT_P3                                                          3
.....

#define GPIO_PIN0                                                      (0x0001)
#define GPIO_PIN1                                                      (0x0002)
#define GPIO_PIN2                                                      (0x0004)
#define GPIO_PIN3                                                      (0x0008)
#define GPIO_PIN4                                                      (0x0010)
#define GPIO_PIN5                                                      (0x0020)
.....

so that an LED on Port 2.3 would require a function call like this:

GPIO_setAsOutputPin(GPIO_PORT_P2, GPIO_PIN3);

and the solution to the OP's question is to define a macro that expands a single identifier into the entire parameter set for the function call. Example:

// MSP430Ware Driverlib GPIO macro example

// Port/Pin Expansion Macro
#define MY_LED    GPIO_PORT_P2,GPIO_PIN3

// Configure the LED pin
GPIO_setAsOutputPin(MY_LED);

// Turn LED on
GPIO_setOutputHighOnPin(MY_LED);

// Turn LED off
GPIO_setOutputLowOnPin(MY_LED);

// Toggle the LED
GPIO_toggleOutputOnPin(MY_LED);

Good idea.

However, I don't like the fact that it still is a function call.

Instead of a single 5-cycle 3-word instruction which is not even clobbering a processor register, it is a function call with clobbering of the parameter registers, and some runtime calculations that could be done by the compiler at compile time, if it were a macro.

 I wonder how a simple endless loop over the toggle function performs, compared to a loop over a simple XOR. A factor of ten times slower? or worse?