RPI Pico - Interrupt Latency under Arduino Framework

Just how fast are interrupts serviced on a Pico running the Arduino framework? Fast enough!

I sort of have the Arduino environment for the RP2040 setup in VSCode thanks to PlatformIO. But, not totally, just yet.

I made a basic sketch registering a falling edge interrupt on GPIO0 of the Pico:

#include <Arduino.h>

void blink();

void setup() {
  // put your setup code here, to run once:
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(2, OUTPUT); // Toggle in ISR 
  pinMode(0,INPUT_PULLUP);
  attachInterrupt(0, blink, FALLING );
  gpio_pull_up(0);
}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
}

void blink() {
  //Perform an atomic bitwise XOR on GPIO_OUT, i.e. GPIO_OUT ^= wdata 
  *(volatile uint32_t *)(SIO_BASE + 0x1c ) = 1<<2; // Toggle GPIO2
}

In the ISR I toggle GPIO2 using the atomic xor GPIO write register. 

I measured the interrupt latency to be approximately 1.5 us:

With just an empty task loop, the ISR jitter was approximately 50 ns:

The maximum continuous interrupt frequency appears to be 150 kHz. Beyond 150 kHz the Pico can't keep up:

I think this is more than adequate to service a I2C/SPI sensor interrupt.