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MSP430F5632: Pin assignment and changing pin value

David Blanco
Prodigy 40 points
Part Number: MSP430F5632
Other Parts Discussed in Thread: MSP430F147

I have much code written for other compilers and I want to use the same code for the MSP430F5632. I want to use this style code DisplayRESET = 0; where DisplayRESET is a single pin.  Here is the struct and #defines I have:

struct BitMapping
    {
    unsigned
    Bit0:1,
    Bit1:1,
    Bit2:1,
    Bit3:1,
    Bit4:1,
    Bit5:1,
    Bit6:1,
    Bit7:1;
    }CHR;

#define  Port1_2Base     0x200
#define  Port2OUTCHAR      ( * (char *)Port1_2Base + 0x03)
#define  Port2OUT                  ( * (struct BitMapping *)Port1_2Base + 0x03)

#define  Port5_6Base        0x240
#define  Port5OUT                 ( * (struct BitMapping *)Port5_6Base + 0x02)
#define  Port6IN                     ( * (struct BitMapping *)Port5_6Base + 0x01)
#define  Port6OUT                 ( * (struct BitMapping *)Port5_6Base + 0x03)

#define  Port7_8Base        0x260
#define  Port7IN                      ( * (struct BitMapping *)Port7_8Base + 0x00)
#define  Port7OUT                  ( * (struct BitMapping *)Port7_8Base + 0x02)


#define    DisplayCD    Port6OUT.Bit6
#define    DisplayCE    Port7OUT.Bit7
#define    DisplayWR    Port7OUT.Bit6
#define    DisplayData  Port2OUT.CHR
#define    DisplayRD    Port6OUT.Bit7
#define    DisplayRESET Port5OUT.Bit6

When I compile, everywhere I use a display pin like:

DisplayCD = 0;

I get:

Description    Resource    Path    Location    Type
#42 expression must have arithmetic or pointer type    DisplayRoutines.c    /HRX MSP Ccode/MSP HRX CCODE    line 89    C/C++ Problem

I have not found any examples of pins being used like this.  It's all:

DisplayCD |= BIT6;

or

DisplayCD &=~BIT6;

What do I need to do to use:

DisplayCD = 0;

  • 0
    Guru 35690 points

    Have you tried *DisplayCD?

  • 0 in reply to Keith Barkley
    Prodigy 40 points

    Just tried it, doesn't work.

  • 0 in reply to David Blanco
    TI__Genius 9970 points

    Hi David,

    This is in interesting question. I'm unsure if there is an easy way to do this on MSP430. The reason is a bit set/clear requires a readback of the GPIO PxOUT register. Hence the need for "|=" (which is just x = x | y).  As far as I know there isn't a single C operation that can do this. 

    The BitMapping struct is neat but I've never seen the ":1" notation before. Can you point me at a reference that describes how this works?

    What compiler/MCU have you been able to use this software paradigm with?

    Regards,

    Evan

  • 0 in reply to Evan Lew
    Guru 35690 points

    Standard C. It is a bitfield. Section 6.9 (pg 149) in K&R 2ed. 8^)

  • 0 in reply to Evan Lew
    Prodigy 40 points

    Quadravox with an MSP430F147 and MSP430F2402

    Is there a setting in the compiler I'm missing or something?

    My computer with the Quadravox died so I'm trying to move all my code to TI's code composer.

  • 0 in reply to David Blanco
    Prodigy 40 points

    FOUND IT!!!

    Compiler does not like calculating addresses. Just by chance I tried:

    #define  Port5OUT          ( * (struct BitMapping *)0x242)
    #define  Port6IN              ( * (struct BitMapping *)0x241)
    #define  Port6OUT          ( * (struct BitMapping *)0x243)

    and my errors went away.  Somehow calculating the address works in  msp430f5632.h which is part of the compiler.

  • 0 in reply to David Blanco
    TI__Genius 9970 points

    Hi David, 

    I was able to make it work with a couple modifications to your original code:

    #include <msp430.h>


struct __attribute__((__packed__)) BitMapping
    {
    unsigned
    Bit0:1,
    Bit1:1,
    Bit2:1,
    Bit3:1,
    Bit4:1,
    Bit5:1,
    Bit6:1,
    Bit7:1;
    }CHR;

#define  Port1_2Base     0x200
#define  Port2OUT        ( (struct BitMapping *)Port1_2Base + 0x03)



int main(void)
{
  WDTCTL = WDTPW+WDTHOLD;                   // Stop WDT

  P2DIR |= 0xFF;

  while (1)
  {
     Port2OUT->Bit5 = 1;
     __delay_cycles(1000);
     Port2OUT->Bit5 = 0;
     __delay_cycles(1000);
  }

}

    The key changes:

    1. Use struct __attribute__((__packed__)) BitMapping to get the compiler to understand the bit packing intention
    2. Removed the * in front of the Port2OUT inside the #define
    3. Use the '->' notation instead of '.'

    I was able to see the pin toggel in my example :) Happy coding.

    Evan

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