• Category Archives programing
  • msp430- coding interrupts for mspgcc

    I am just an idiot, but thats my opinion. For those with MSPGCC compilers, we have a more difficult time finding code examples, and many of the code examples given either don’ explain very well (cryptic Coding, un-commented code) or they are for the CCS or IAR, and they dont use the same syntax as the MSPGCC compiler. So here is how to create an interrupt handler for non-PUC/POR interrupts.

    I will not go into interrupt vector masking, that is beyond me at this moment, but im not saying that i wont cover it later on, once i understand why you would want to mask it…..
    So lets start at what headers and other setup items you need before, creating the interrupt handler.
    First the signal.h has to be included into your code. #include<signal.h>
    this will give you access to the special function of
    interrupt(VECTOR ) service_routine (void) {/*interrupt code*/ }

    this is the same as #pragma vector=WDT_VECTOR
    __interrupt void watchdog_timer(void){ }

    These are the Defined vectors for interrupts right from the header files.(mspgcc headers)

    #define PORT1_VECTOR 4 /* 0xFFE4 Port 1 */
    #define PORT2_VECTOR 6 /* 0xFFE6 Port 2 */
    #define USI_VECTOR 8 /* 0xFFE8 USI */
    #define ADC10_VECTOR 10 /* 0xFFEA ADC10 */
    #define TIMERA1_VECTOR 16 /* 0xFFF0 Timer A CC1-2, TA */
    #define TIMERA0_VECTOR 18 /* 0xFFF2 Timer A CC0 */
    #define WDT_VECTOR 20 /* 0xFFF4 Watchdog Timer */
    #define NMI_VECTOR 28 /* 0xFFFC Non-maskable */

    all the interrupts should be self expainatory, vector = the source of the interrupt.

    since now we have all the basics we can now right a small program that uses interrupt, we will just create a small WDT interval timer.
    /*WDT interval timer- code based on msp430 examples*/
    #include<signal.h> //interrupt service routine
    #include <io.h> //usually included on msp430 header, but for sfr register access.
    void main(void) {
    WDTCTL = WDT_MDLY_32; //~30mS intervals
    P1DIR |=BIT1;
    IE1 |= WDTIE; //enable interrupt
    _BIS_SR(LPM0_bits + GIE); //not low power mode and enable interrupts
    }//end of main
    //interrupt service routine
    interrupt(WDT_VECTOR) watchdog_timer(void)
    P1OUT ^= BIT1;
    }//end of interrupt

    this should give you a good start on your Interrupts but there is still one thing that you may need. Changing the power modes when a interrupt is being serviced, the power mode will revert back to the power mode that it was in when the interrupt was called.
    There are 2 functions that we can use to clear or set power modes while in an interrupt.
    First one is to set the mode on exit of the routine, this is done by changing the copy of the status register that is saved to the stack. _BIS_SR_IRQ( ... )
    you would use this the same way you would use the _BIS_SR(…)

    The second one will clear the bits you select _BIC_SR_IRQ(...) same usage as the other, except it will just clear the bits not modify them.
    ***the use of _BIx_SR_IRQ() should only be used in an interrupt service request, the compiler will give you a warning but will produce the correct code if you use it anywhere else.***
    ****remember to enable Interrupts by using BIS_SR(GIE) or eint()****

    Edit 6-23-2011

    MSPGCC Uniarch branch of mspgcc has been released, It supports newer chips like the msp430G2453 (the newer 20pin DIPs) This is an initiative to unify the current branches of mspgcc. Interrupts for this version is slightly different. Once I test it or get confirmation from another user I will post the correct format for uniarch branch……but what would be better would be unify the branches so we don’t have so much confusion with these version discrepancies and nuances of the trees.

    As of right now uniarch is still being worked on and there and is not fully recommended unless you need support for the newer 20pin Dips (G2x53 G2x52).  Please don’t let my opinion dissuade your choice of compiler, mspgcc works great for me but uniarch may work better for you.


    Thank you Tissit for your Comment

    “In current gcc, you can (should) include msp430.c instead of the specific header and use the -m switches (in a Makefile) to tell the compiler which chip you’re using. It will find the right headers automatically. “

    If I forget something let me know and I will update

  • MSP430 basic coding/programing part 2 WDT+

    WDT is a very useful tool, as I explained before most of us will turn it off or use it as an interval timer. Timer_A has a similar timer function but more robust and more options.
    So today we will be going over WDT and timer_A registers, how to setup them up, how you use them is up the you.

    WDT is the watch dog timer, used for checking errors/faults, or software states, interval timer, interval interrupt, or what ever other uses you can think of.

    So lets start with the basic register WDTCTL
    This is the main register that will configure the WDT, bits 15-8 are the password register and 7-0 are for control. you need to set the password register before you can modify bits 7-0.
    to do this WDTCTL = WDTPW; // WDTPW = 0x5A00 or 01011010 00000000
    This will allow access to the 7-0 bits to configure the WDT. The rest of the registers are used to turn off, setup, change to interval mode, set interupts, change clock sources, and more.
    This next set of registers is taken from the slau144e.pdf from the TI website, this book explains how it all works and what the settings mean.

    WDTHOLD Bit 7 Watchdog timer+ hold. This bit stops the watchdog timer+. Setting
    WDTHOLD = 1 when the WDT+ is not in use conserves power.

  • 0 Watchdog timer+ is not stopped
  • 1 Watchdog timer+ is stopped
  • WDTNMIES Bit 6 Watchdog timer+ NMI edge select. This bit selects the interrupt edge for the
    NMI interrupt when WDTNMI = 1. Modifying this bit can trigger an NMI. Modify
    this bit when WDTIE = 0 to avoid triggering an accidental NMI.

  • 0 NMI on rising edge
  • 1 NMI on falling edge
  • WDTNMI Bit 5 Watchdog timer+ NMI select. This bit selects the function for the RST/NMI pin.

  • 0 Reset function
  • 1 NMI function
  • WDTTMSEL Bit 4 Watchdog timer+ mode select

  • 0 Watchdog mode
  • 1 Interval timer mode
  • WDTCNTCL Bit 3 Watchdog timer+ counter clear. Setting WDTCNTCL = 1 clears the count
    value to 0000h. WDTCNTCL is automatically reset.

  • 0 No action
  • 1 WDTCNT = 0000h
  • WDTSSEL Bit 2 Watchdog timer+ clock source select

  • 0 SMCLK
  • 1 ACLK
  • WDTISx Bits 1-0
    Watchdog timer+ interval select. These bits select the watchdog timer+
    interval to set the WDTIFG flag and/or generate a PUC.

  • 00 Watchdog clock source /32768
  • 01 Watchdog clock source /8192
  • 10 Watchdog clock source /512
  • 11 Watchdog clock source /64
  • Continue reading  Post ID 511

  • MSP430 basic coding/programing part 1

    basic functionality can be achieved with minimal coding. In my attempt to learning how to get the different peripherals working on my msp~2231. All MSP430 value line come with a simple universal package of hardware, Basic Clock, Timer_A, GPIO, USI (SPI,I2C,UART), WDT. then there are chips with chip specific hardware like ADC10, Comparator, Timer_B, Sigma-Delta ADC. to get most of these to work, it takes very little code, but to make them useful that will take a little more skill.

    We will start with everything after the header file #include msp430xxx.h , remember that this header file is chip specific.

    Lets start Here- this is where most of your code will go, including setting up the clocks, pins, interrupts, and anything else that will be run.
    void main(void) {
    //program goes here

    Continue reading  Post ID 511