Basic MSP430 GPIO Macros

[Fred 453]

Interesting stuff. I was thinking about this only yesterday, primarily because I have a project that I switch between a F5529LP dev board and a F5510 final PCB. That means it's helpful to be able to switch pins and ports with some sections like this

 

#if defined (__MSP430F5510__)
#define LED_RED_PORT	P2OUT
#define LED_RED_PIN 	BIT1
#endif

#if defined (__MSP430F5529__)
#define LED_RED_PORT P1OUT
#define LED_RED_PIN BIT0
#endif

Usage:
  LED_RED_PORT |= LED_RED_PIN;

This simple stuff is all fine, but gets messy when using interrupts and needing to define multiple PxDIR, PxIN, PxOUT, PxSELn, PxIE, etc.

 

Then I started doing this sort of thing, but it started to feel a bit wrong

#define IRQ_ON P2IE |= IRQ_PIN

Usage:
  if (something)
    IRQ_ON;

I might just use the parameterized macros with ## such as GPIO_SEL(x) so I only have to define the port once. I knew I'd seen something similar once, but couldn't remember where or when. Thanks for reminding me.

[Fred 453]

Anyone know what I'm doing wrong here?

#define LED_PORT    1
#define PxOUT(port) P##port##OUT

PxOUT(LED_PORT) ^= 0x01;

I get a compilation error - identifier "PLED_PORTOUT" is undefined.

 

I can see that the value that I pass to the parameterized macro is taken literally rather than being itself defined as 1. How do I tell the preprocessor to make the substitution?

 

My code looks similar to that above. I've tried changing the ordering, whitespace, throwing in brackets. I can't seem to get it to work.

[Fred 453]

Ah - Just after I posted I managed to find an answer myself although it's not elegant. It seems that to expand again you need another level of redirection.

http://stackoverflow.com/questions/12630548/c-expand-macro-with-token-pasting

 

This works because of the first rather pointless looking line:

#define PxOUT(port)   PxOUT_(port)
#define PxOUT_(port)  P##port##OUT
#define LED_PORT      1

PxOUT ( LED_PORT ) ^= 0x01;

If anyone knows a slightly neater solution then let me know, but this will do.

[enl 227]

 

Welcome to the preprocessor. I don't know of any more elegant solution as parameters are literal, though there may be one. The second level forces the parameter to be seen as a token itself and be substituted. The initial version did not let the token be seen on its own.

 

I learned the power, and limitations, or macro expansion with asmh on MVS, writing a 12 liner to expand to the twelve days of xmas for a class. The C/C++ preprocessor is more capable, but is still not doing full featured regeps.

 

 

If anyone knows a slightly neater solution then let me know, but this will do.

[tonyp12 26]

As all gio registers start with port and then OUT, IN, IE etc, example: P1OUT, with some macro word scrambling you can do this:

#define read &           // words for common gpio interaction
#define clear &= ~
#define set |=
#define toggle ^=

#define Button1(y,x)    (P1 ##x y BIT0)       // PORT and PIN (ignore the ##x y)
#define BlueLED(y,x)    (P2 ##x y BIT5) 

To use them:
BlueLED(set,DIR);                                 
BlueLED(clear,OUT);

Button1(clear,DIR);                       // a input
Button1(set,OUT);                         // pull-up resistor
Button1(set,REN);                          
Button1(set,IES);                         // falling edge
button1(clear,IFG);
Button1(set,IE);                            

[Clavier 34]

This is how I do my GPIO initialization. It doesn't handle any later GPIO accesses, but it's a nice table, and smaller and faster than configuring the bits one by one.

/* use 0 or 1 to set the output level */
#define OUTPUT        0x00    /* default */
#define INPUT         0x02
#define PULL_DOWN     0x04
#define PULL_UP       0x05
#define REDUCED_DRIVE 0x00    /* default */
#define FULL_DRIVE    0x08
#define GPIO          0x00    /* default */
#define PERIPHERAL    0x10

struct digital_io_init_f5529 {
    u8 P1[8];
    u8 P2[8];
    u8 P3[8];
    u8 P4[8];
    u8 P5[8];
    u8 P6[8];
    u8 P7[8];
    u8 P8[3];
    u8 PJ[4];
};

static void init_port(const u8 *init, unsigned int count, uint16_t int base_address)
{
    uint16_t out = 0, dir = 0, ren = 0, ds = 0, sel = 0;
    uint16_t bit;

    for (bit = 1; count > 0; init++, bit <<= 1, count--) {
        if (*init & 1)          out |= bit;
        if (!(*init & INPUT))   dir |= bit;
        if (*init & PULL_DOWN)  ren |= bit;
        if (*init & FULL_DRIVE) ds  |= bit;
        if (*init & PERIPHERAL) sel |= bit;
    }
    HWREG16(base_address + OFS_PAOUT) = out;
    HWREG16(base_address + OFS_PADIR) = dir;
    HWREG16(base_address + OFS_PAREN) = ren;
    HWREG16(base_address + OFS_PADS ) = ds;
    HWREG16(base_address + OFS_PASEL) = sel;
}

static void init_ports(const struct digital_io_init_f5529 *init)
{
    init_port(init->P1, 8 + 8, PA_BASE);
    init_port(init->P3, 8 + 8, PB_BASE);
    init_port(init->P5, 8 + 8, PC_BASE);
    init_port(init->P7, 8 + 3, PD_BASE);
    init_port(init->PJ, 4,     PJ_BASE);
}

void init()
{
    init_ports(&(const struct digital_io_init_f5529){
           .P4[4] = PERIPHERAL | OUTPUT,
           .P4[5] = PERIPHERAL | INPUT,
           .P7[0] = GPIO | INPUT | PULL_UP,
           .P7[1] = GPIO | OUTPUT | FULL_DRIVE,
           /* ... */
    });
}