__builtin_propeller_waitcnt()

Comments

• macca Posts: 894

  2017-03-17 19:38

  It is the equivalent of waitcnt target, param1 in pasm.
  To get the same functionality, you need to use the return value of __builtin_propeller_waitcnt which is target+param1, since In C parameters are passed by value so any modification is local to the function.
  
  See also the waitcnt and waitcnt2 helper functions.
  
• ersmith Posts: 6,184

  2017-03-17 21:23

  JonnyMac wrote: »

  What is the purpose of param1 in __builtin_propeller_waitcnt(target, param1)?

  
  It's used to update the target time for the next waitcnt:

    targetCnt = CNT + freq; // set up initial interval
    do {
        // do something useful that takes less than "freq" cycles
        ...
        // now sleep until interval is finished
        targetCnt = __builtin_propeller_waitcnt(targetCnt, freq);
        // targetCnt has been updated to the next CNT to wait for
     } while (condition);
  
• JonnyMac Posts: 9,376

  2017-03-17 22:24 edited 2017-03-17 22:24

  SMH. I should have known that. Thanks!