k07mutexceiling.ino

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//220216
#include <krnl.h>
// one task loops and blink
// k_wait ensures proper timing
 
struct k_t *p1, *p2, *s1, *semmutex;
 
// shared data
struct shDataTp {
  int v;
  int counter;
};
 
struct shDataTp  sharedData = {0, 0};
 
void saveDataInCritRegion(int v)
{
int retV;
/*
k_mut_ceil_enter
 @return : 0 if you have been waiting, 1 if you just went through, -1 for
   timeout, -4 if your priority was higher than ceiling priority so you were aborted
*/
  retV =  k_mut_ceil_enter(semmutex, 0);
  if (0 <= retV ) {
    sharedData.v = v;
    sharedData.counter ++;
    k_mut_ceil_leave(semmutex);
  }
  Serial.print("enter retV ");
  Serial.println(retV);
}
 
struct shDataTp getDataInCritRegion(void)
{
  struct shDataTp tmp;
  if (0 <= k_mut_ceil_enter(semmutex, 0) ) {
    sharedData.counter--;
    tmp = sharedData;
    k_mut_ceil_leave(semmutex);
  }
  
  return tmp; // also if no data has been picked up ...
}
 
// the sampler task
void t1()
{
  int v;
  k_set_sem_timer(s1, 100);
  while (1) {
 
    k_wait(s1, 0); //wait until  a kick comes
 
    v = analogRead(A0);
    saveDataInCritRegion(v);
  }
}
 
void t2()
{
  static struct shDataTp v;
  while (1) {
 
    k_sleep(345);
    v = getDataInCritRegion();
    Serial.print(v.v);
    Serial.print(" ");
    Serial.println(v.counter);
  }  // do we keep up in pace ?
}
 
#define STK 110
char a1[STK],a2[STK];
 
void setup()
{
  int res;
  Serial.begin(115200);
  while (! Serial) ;
  pinMode(13, OUTPUT);
 
  k_init(2, 2, 0); // init with space for one task
  //         |--- no of mg Queues (0)
  //       |----- no of semaphores (0)
  //     |------- no of tasks (2)
 
  // priority low number higher priority than higher number
  p1 = k_crt_task(t1, 10, a1,STK); // t1 as task, priority 10, 100 B stak
  p2 = k_crt_task(t2, 10, a2,STK); // t1 as task, priority 10, 100 B stak
 
  s1 = k_crt_sem(0, 10); // tik
  semmutex = k_crt_mut(5,1, 10); // ceiling prio == 5 
  
  Serial.println("bef start");
  res = k_start(); // 1 milli sec tick speed
  // you will never return from k_start
  Serial.print("ups an error occured: "); Serial.println(res);
  while (1) ;
}
 
void loop() {}