[properparity]

>For comparison, Microchip (formerly atmel) SAMD21 (also Cortex-M0+, of Arduino Zero fame) is about 3-4 $, single core, less RAM.

But it has built in flash.

Sure, external flash is still cheaper* (512K for ~$0.2) but it's a major downside having a mandatory extra chip because of how much more physical space it takes up.

* Might not actually be cheaper if you consider pick&place cost of an extra part you're not likely to use anywhere else.

[mmoskal]

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.

edit: typo