Teensy 4.1 interrupts at multi-MHz speed using TeensyTimerTool

As shown in our example Teensy 4.1 PlatformIO 2MHz Timer interrupt GPIO output you can use TeensyTimerTool to generate multi-MHz timer interrupts. In our experiments, we could generate GPIO-toggling interrupts up to 4 MHz:

The trick here is to use std::chrono time literals. The TeensyTimerTools PeriodicTimer example only shows us how to use microsecond resolution:

t1.begin(callback, 250'000); // 250ms

but we can simply use 250ns to obtain nanosecond resolution:

t1.begin(callback, 250ns);

Here’s our observation what works and what doesn’t:

• Multi-MHz GPIO-toggling interrupts as shown in our example only work on GPT1 and GPT2, they do NOT work on PIT and TMRx. We did not investigate the precise reasoning behind this, and there might also be ways to
• As usual, the interrupt must only contain a small number of instructions. We’re using digitalWriteFast(), but using direct register access would be even faster.