Posted on May 17, 2011 at 15:12Your question has no solution, if it's literally taken.
Even Arduino milli() or micro() functions use an interrupt routine...
To make things clear, the following code is taken from:
arduino-0022-src.tar.gz\arduino-0022\hardware\arduino\cores\arduino\wiring.c
// the prescaler is set so that timer0 ticks every 64 clock cycles, and the
// the overflow handler is called every 256 ticks.
#define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256))
// the whole number of milliseconds per timer0 overflow
#define MILLIS_INC (MICROSECONDS_PER_TIMER0_OVERFLOW / 1000)
// the fractional number of milliseconds per timer0 overflow. we shift right
// by three to fit these numbers into a byte. (for the clock speeds we care
// about - 8 and 16 MHz - this doesn't lose precision.)
#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3)
#define FRACT_MAX (1000 >> 3)
volatile unsigned long timer0_overflow_count = 0;
volatile unsigned long timer0_millis = 0;
static unsigned char timer0_fract = 0;
SIGNAL(TIMER0_OVF_vect)
{
// copy these to local variables so they can be stored in registers
// (volatile variables must be read from memory on every access)
unsigned long m = timer0_millis;
unsigned char f = timer0_fract;
m += MILLIS_INC;
f += FRACT_INC;
if (f >= FRACT_MAX) {
f -= FRACT_MAX;
m += 1;
}
timer0_fract = f;
timer0_millis = m;
timer0_overflow_count++;
}
unsigned long millis()
{
unsigned long m;
uint8_t oldSREG = SREG;
// disable interrupts while we read timer0_millis or we might get an
// inconsistent value (e.g. in the middle of a write to timer0_millis)
cli();
m = timer0_millis;
SREG = oldSREG;
return m;
}
unsigned long micros() {
unsigned long m;
uint8_t oldSREG = SREG, t;
cli();
m = timer0_overflow_count;
#if defined(TCNT0)
t = TCNT0;
#elif defined(TCNT0L)
t = TCNT0L;
#else
#error TIMER 0 not defined
#endif
#ifdef TIFR0
if ((TIFR0 & _BV(TOV0)) && (t < 255))
m++;
#else
if ((TIFR & _BV(TOV0)) && (t < 255))
m++;
#endif
SREG = oldSREG;
return ((m << 8) + t) * (64 / clockCyclesPerMicrosecond());
}
As you can see, the millis() and micros() functions use timer0_overflow_count and read the TIMER0 value.
If you want to replicate them, TIM4 is alike Arduino's timer0.
As regards your code, you have to follow what wiring.c does: handle TIM4 overflow interrupt and read TIM4 in millis() and micros() code.
regards
EtaPhi
