manitou
Senior Member+

Re: GPS PPS frequency with Rubidium 10mhz to pin 14 and a GPS PPS to pin 15, what response do you see? Do you have a GPS with external antenna and good view of sky?

You can paste in sketch with code tags (click on #) // Code to test Teensy 4.0 GPT2 Counter with External Clock void setup() { // Setup USB serial port so we can print the timer value ...

another pendulum frequency thread: https://forum.pjrc.com/threads/65156-Pendulum-clock-accuracy-GPSDO-10Mhz-1Hz-pulse

here is small sketch to test GPT with external clock (pin 14) and and capture with pin 15 // GPT2 external clock (GPS 8 mhz) into pin 14, PPS captured to pin 15...

Dang, though the question is mute, maybe using static volatile for a and b will avoid the compiler optimizations; static uint64_t cnt = 0; static volatile uint64_t a, b; void check(uint64_t x, uint64_t y) { if...

No Teensy 4 compare failures with this sketch with arduino 1.8.19 and teensyduino 1.58 static uint64_t cnt = 0; void check(uint64_t x, uint64_t y) { if (x != y) { Serial.printf("ERROR %llx %llx cnt =...

Please try and develop a small test code that demonstrates the problem.

Please provide a runnable sketch that demonstrates the problem. What IDE and OS are you using? what optimizations (compiler settings) are you using?