Accuracy is pretty good, see committed comments :-)
Code used for testing, in main():
uint32_t i;
SET_OUTPUT(PIO0_1);
while (1) {
// 10 seconds for each frequency, so we
// can measure all three with one upload.
for (i = 10000; i > 0; i--) {
WRITE(PIO0_1, 1);
delay_us(1000);
WRITE(PIO0_1, 0);
delay_us(1000);
}
for (i = 1000; i > 0; i--) {
WRITE(PIO0_1, 1);
delay_us(10000);
WRITE(PIO0_1, 0);
delay_us(10000);
}
for (i = 200; i > 0; i--) {
WRITE(PIO0_1, 1);
delay_us(65000);
WRITE(PIO0_1, 0);
delay_us(65000);
}
}
(Hopefully) no functional change.
Also remove these wd_reset()s in delay_us() to match the behaviour
promised in delay.h. Not that this matters much, watchdog is
disabled by default.
See comments in the code for the result.
This also fixes a bug where corner cases like delay(0) or
delay(13107) whould result in an extra long pause.
Note: 65535 / (F_CPU / 4000000) = 13107 on 20 MHz.
This costs 28 bytes binary size.
function.
Inline delay functions and change base function to
use __builtin_avr_delay_cycles(). Generated delays
are at least as long as the requested delay and
compensate for the system clock (based on F_CPU).
Delay functions must be called with constant values.
A compile time error is issued if they are not.
Delay.c removed as it is no longer used.
Nico Tonnhofer
Markus Hitter
Jim McGee
Michael Moon