Re: [avr-gcc-list] 32-bits time

[Bjarne Laursen]

A few additions to David Kelly's code:

inline uint32_t timer32_now(void)
{
   int8_t sreg;
   union {
       struct {
           uint16_t lo, hi;
       } w;
       uint32_t l;
      uint8_t b[4]; // <------ added: access as bytes
   } temp;

   sreg = SREG;
   cli();
   temp.w.lo = TCNT1;
   temp.w.hi = hiword_time;
            // --------- if TOV1 gets set here, temp will not need any 
correction, this is indicated by  temp.w.lo close to 0xFFFF
   //  check for unserved Timer1 Overflow
   if( TIFR & (1<<TOV1) )
     if (temp.b[0] < 128) // <-----------added: check if temp is 
wrapped around
       temp.w.hi++;        // do what hasn't yet been done in  
SIG_OVERFLOW1

   SREG = sreg;

   return( temp.l );
}


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I think that the code from Galen Seitz works too.
It is more simple, but the exact sampletime of the clock will vary a little.
Since you chose prescaler=1 you might need the higher precision. I don't 
know.