MSP430FR2355: generating soft ISRs???

Steve Wenner

Part Number: MSP430FR2355

hello....

I have a UART which receives a command. Main wakes up and processes/acts on the command. I then need to circle back around to use a function at the beginning of main to put together a command packet to send. The problem is after I act on the incoming UART and then circle back to the beginning of main I go into LPM3 and never get to the second function to build a packet because ISRs are not occurring at this time. What is the best way to handle this? Assuming I use an unused I/O and generate an IRQ, how do I do this when my uart rcv processing function lies somewhere in the middle of code? If my function generates IRQ I will go off come back and still process commands before I get to the end of main at which point I am no better off because the first line of main is LPM3....

In short my rcv processing function AND the function I need to build messages are somewhere within main. Main only wakes up after ISRs of which I will have none after rcv processing function.

After configuration beginning of main loop

    while(1)
    {
        LPM3;

over 4 years ago

0 Leonardo Estevez over 4 years ago

TI__Genius 12615 points

Hi Steve,

Here's a related thread on soft interrupts:

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/198624/how-to-generate-software-interrupt-in-msp430?tisearch=e2e-sitesearch&keymatch=MSP430F1610

According to this thread, you should be able to set an interrupt flag, so no need to generate an external trigger via GPIO:

https://e2e.ti.com/support/microcontrollers/msp-low-power-microcontrollers-group/msp430/f/msp-low-power-microcontroller-forum/137409/software-interrupt

I don't currently have any other insight into how to address the problem you're describing.

Hope this helps.

BR,
Leo

0 Bruce McKenney over 4 years ago

Guru 100745 points

I'm not completely sure what your concern is but some thoughts:

1) In most cases, it is possible to explicitly set an IFG and have the pertinent ISR invoked. (As I recall, you've used this feature.)

2) You haven't provided much context, but even that fragment seems odd since typically an LPM call would be nearer to the bottom of the home-loop, after you've run out of work to do. A typical home-loop might look like:

while (1) {
   do_work_1();
   do_work_2();
   __disable_interrupt();         // (Avoid race)
   if (work_to_do()) {            // New work in the meantime?
      __enable_interrupt();
      continue;                   // Go try again
   }
   __bis_SR_register(LPM3_bits | GIE); // Sleep until work to do
}

which keeps circling back until no new work has arrived, and only then goes into LPM.

0 Steve Wenner over 4 years ago in reply to Bruce McKenney

Genius 3240 points

Yes Bruce I have used soft interrupts....My loop is 180 degrees opposite....

That is I set LPM3 at the top and wait for IRQs to fire. The IRQs set 'soft' process flags. I then service these flags. Some of these flags finish by setting another process flag which is further down in the loop....finally after a pass I get to bottom of loop and then go back into LPM3. in this case I have a process going off at the end of the loop that needs to then run a process that is in the middle of the loop...I was able to figure it out though because I created a 'soft' ISR on a gpio input by setting the IFG flag at the very end of the while(1) loop which wakes main.

**Attention** This is a public forum

MSP low-power microcontrollers

MSP low-power microcontroller forum

MSP430FR2355: generating soft ISRs???