How to get MSP430 Code to work without using libraries?

Question

Ok so I am trying to ditch energia texas instruments arduino style ide and I have used IAR for coding a Tiva C series development board where I was able to use pointers to memory locations to perform specific things like toggling led for example. I have had a hard time doing the same on a dev board running a MSP430FR5994 mcu, I know the memory address of the green led pin to be PORT 1 PIN 1 OR P1.1 on the board. I also have included the msp430.h header file for an api to the board from my ide. What I don't understand is why when in debug my code is changing the value of the correct registers to the correct numbers but it is not altering the board. I have also verified that it is connected to the board as it will not proceed to debug with it unplugged. My direct questions are this: 1 I should be able to alter memory locations with no headerfiles or any special api's as long as I know the specific addresses correct? 2 I did not see anything about clock gating in the data sheet and in debug I can see those registers changing values so is there something other than setting the pin direction and value that I need to do?( the default pin function is generic gpio I checked so I left that register alone. Any ideas or pointing out obvious errors in my approach would be very helpful thanks. In the code below I used the header file names as I could not get the direct pointers to work. Also I was confused by the data sheet as the base address for port 1 was written as 0200H which is 5 hex numbers when I was expecting 4 since the chip is 16bit system? I assumed with the offsets it meant 0x202H etc am I incorrect in this assumption? registers during debugging image

ti.com/lit/ds/symlink/msp430fr5994.pdf (datasheet port 1 mem locations page 130)

#include <msp430.h> 
/**
 * main.c
 */
int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;   // stop watchdog timer
    while(1){
    int i ;
    int j ;

    P1DIR = 2;
    //*((unsigned int *)0x204Hu) = 2;

    P1OUT = 2;
    //*((unsigned int *)0x202Hu)= 2;
    for( i = 0; i< 2 ; i++){}

    P1OUT = 0;
    //*((unsigned int *)0x202Hu)= 0;

    for (j = 0 ; j< 2; j++){}


    }

    return 0;
}

0200H is 16 bits 4 hex numbers. and yes in that context 0200H = 0x0200 = 0x200 = 0b0000001000000000 = 512 — old_timer
if you are trying to blink an led unless you have this on a scope you wont see it you need a longer delay and something that the optimizer if you turn on wont remove as dead code. — old_timer
you are on the right track though. make the pin an output then in a loop do the on delay, off delay thing — old_timer
'H' is not a hexadecimal value. It's datasheet shorthand for "hexadecimal". "0200h" means the same as "0x0200". — kkrambo
Do you see the LED toggle if you single-step through the code with the debugger? — kkrambo

kkrambo kkrambo · Accepted Answer · 2020-04-16T21:53:24

See section 12.3.1 of the MSP430FR59xx User's Guide.

After a BOR reset, all port pins are high-impedance with Schmitt triggers and their module functions disabled to prevent any cross currents. The application must initialize all port pins including unused ones (Section 12.3.2) as input high impedance, input with pulldown, input with pullup, output high, or output low according to the application needs by configuring PxDIR, PxREN, PxOUT, and PxIES accordingly. This initialization takes effect as soon as the LOCKLPM5 bit in the PM5CTL register (described in the PMM chapter) is cleared; until then, the I/Os remain in their high-impedance state with Schmitt trigger inputs disabled.

And here is the example blinky code provided in the MSP430FR599x Code Examples available to download from here.

#include <msp430.h>

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

    // Configure GPIO
    P1OUT &= ~BIT0;                         // Clear P1.0 output latch for a defined power-on state
    P1DIR |= BIT0;                          // Set P1.0 to output direction

    PM5CTL0 &= ~LOCKLPM5;                   // Disable the GPIO power-on default high-impedance mode
                                            // to activate previously configured port settings

    while(1)
    {
        P1OUT ^= BIT0;                      // Toggle LED
        __delay_cycles(100000);
    }
}

You probably need to add that PM5CTL0 &= ~LOCKLPM5; line to your code.

And then single-step through your code in the debugger to observe the LED. Because if you let your code run at full speed the delay loops are way too short to observe the LED flash with your eye.

How to get MSP430 Code to work without using libraries?

2 Answers