External flash also messes with real-time response times - if your IRQ handler is not forced to be in RAM it can take tens-hundreds of microseconds to start, which in many applications is not acceptable. Built-in flash is much more predictable.
Last time I tried RP2040 SDK (a few months back) many functions you would need to use in these IRQ handlers were not marked as RAM, which means you have to copy&paste them from SDK to your code and add the attribute.
The ESP32 suffers from similar problem, but at least they seem to have been more thoughtful about slapping these RAM attributes here and there.
Having said that, the RP2040 is generally much more pleasant to program than ATSAMD21 or ESP32 and the PIOs are awesome. Also you can easily get it with assembly from JLCPCB at $1.20 or thereabouts.
Last time I tried RP2040 SDK (a few months back) many functions you would need to use in these IRQ handlers were not marked as RAM, which means you have to copy&paste them from SDK to your code and add the attribute.
The ESP32 suffers from similar problem, but at least they seem to have been more thoughtful about slapping these RAM attributes here and there.
Having said that, the RP2040 is generally much more pleasant to program than ATSAMD21 or ESP32 and the PIOs are awesome. Also you can easily get it with assembly from JLCPCB at $1.20 or thereabouts.
edit: typo