Add FLASH option to pico_package_uf2_output

[will-v-pi]

Allows passing FLASH instead of 0x10000000 (eg pico_package_uf2_output(hello_serial FLASH)) to package a UF2 to flash

Also adds a pico_ensure_load_map(TARGET) function, to ensure a load_map is added to the binary (eg for universal no_flash binaries)

[lurch]

Would it also make sense to add an "SRAM" option?

[will-v-pi]

Would it also make sense to add an "SRAM" option?

Not really - packaging is where you put an SRAM binay in Flash, so it can be stored in non volatile memory, and the bootrom copies it to SRAM at runtime. It doesn't make sense to do the opposite and package a Flash binary to SRAM. It might make sense to package an SRAM binary from one bit of SRAM to another, but you'd be specifying a custom address for that anyway.

[lurch]

Perhaps it's also worth making a companion PR to pico-examples demonstrating this feature being used? 🙂 (which obviously can't be merged until this PR has been merged)

[will-v-pi]

Yeah, once this is merged, I'll replace all the pico_package_uf2_output(... 0x10000000) in pico-examples with this

[will-v-pi]

Would it also make sense to add an "SRAM" option?

Not really - packaging is where you put an SRAM binay in Flash, so it can be stored in non volatile memory, and the bootrom copies it to SRAM at runtime. It doesn't make sense to do the opposite and package a Flash binary to SRAM. It might make sense to package an SRAM binary from one bit of SRAM to another, but you'd be specifying a custom address for that anyway.

Actually, looking through the examples, we do use packaging to SRAM for universal binaries, as a way to ensure they have a load map. But rather than adding an SRAM option for this, the better option would be a pico_ensure_load_map function or similar (which pico_package_uf2_output could call)

[kilograham]

I'm a bit confused; you always want to package it into flash, no? so perhaps allowing you to omit the argument is better?

[will-v-pi]

I'm a bit confused; you always want to package it into flash, no? so perhaps allowing you to omit the argument is better?

I've switched it to this, as currently yes, you do always want to package it into flash