5000 microsecond delay inaccurate with either delayMicroseconds() or nrf_delay_us()

Question

I'm using a Seeed Xiao BL:E Sense board with nrf52840 on it. I observed the 5 millisecond delay being off a lot. It was often > 8 ms and changed each time. I used both delayMicroseconds() and nrf_delay_us(). The behaviors were the same. I also tried to disable interrupts just in case, but got no effect. BTW, I measured the delay time by sending pulses through a debug pin. 
 #define DBG_PIN 0

void DBG_pulse(void) {
 digitalWrite(DBG_PIN, HIGH);
 digitalWrite(DBG_PIN, LOW);
 return;
}

void onBLEWrite(uint8_t* buffer, size_t size) {
 ...
 noInterrupts();
 DBG_pulse();
 delayMicroseconds(5000);
 //nrf_delay_us(5000);
 DBG_pulse();
 interrupts();
 ...
} 
 I noticed if I set the delay to under 3 ms, it seemed working fine. But if I set a 3 ms delay followed by a 2 ms delay, the actually delay went back to > 8 ms. Does someone have any ideas?

henryatom · Accepted Answer

Right. A timer interrupt can provide a much more accurate delay in this case. Cheers!

5000 microsecond delay inaccurate with either delayMicroseconds() or nrf_delay_us()

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