Support for avr-dx family

[AasmundN]

As far as I can see there is no support for the newer AVR family avr-dx (avr-db, avr-da and avr-dd). Are there any plans to include these?

[AasmundN]

clangd/clangd#2216

[benshi001]

Are there documents for these devices? I would like to add support for them.

[AasmundN]

Great!🎉

I suppose this could be a place to start for circling in on the differences.

There is also this document describing the instruction set (referenced by the first document).

[benshi001]

Great!🎉

I suppose this could be a place to start for circling in on the differences.

There is also this document describing the instruction set (referenced by the first document).

I find there are only slight differences between the new devices and the classical devices, and there is no change in the instruction set. So I wonder, what are the most needed updates for AVR128DA64 against Atmega128 in llvm?

I thought there might be more job in the AVR-lib than llvm.

[AasmundN]

@benshi001 sorry for the late answer. I am afraid I cannot help you there, I am just getting started with using these controllers myself.

[benshi001]

Each new device has a corresponding compatible old one, please use the old one temporarily.

[tomtor]

There is no architectural difference between eg the attiny1614 (which is supported in current clang) and eg the AVR128DB28, except for bigger memories.

For rust programs on the AVR128DB28 I use:

rustflags = ["-C", "target-cpu=attiny1614", "-C", "link-args=-Wl,--defsym=__TEXT_REGION_LENGTH__=32768", "-C", "link-args=-Wl,--defsym=__DATA_REGION_ORIGIN__=16384", "-C", "link-args=-Wl,--defsym=__DATA_REGION_LENGTH__=16384", "-C", "link-args=-Wl,--defsym=__stack=32767" ]

to specify the memory size (at most 32kB, see next comment), which overrules the 16kB memory size of the attiny1614.

Note that the atmega328 or attiny84 are not compatible with the new devices.
The old devices have the register file at 0x0 - 0x1F, the new devices have IO ports at these locations. This effects IN/OUT instructions and SBI/CBI, so you must specify a modern device (like attiny1614) when generating code for the AVR* devices.

[tomtor]

Note that I changed the rustflags from the previous comment to include the data segment size and origin. For programs >32kB on the avr128db28 use:

rustflags = ["-C", "target-cpu=atxmega128a3", "-C", "link-args=-Wl,--defsym=__DATA_REGION_ORIGIN__=16384", "-C", "link-args=-Wl,--defsym=__DATA_REGION_LENGTH__=16384", "-C", "link-args=-Wl,--defsym=__stack=32767" ]

This will copy readonly data into the 16kB RAM segment. If you need all the RAM you can use the target-cpu=attiny1614 from the previous comment, but you must map the flash segment and your program can be at most 32kB:

dp.CPU.ccp().write(|w| w.ccp().ioreg()); // remove protection
dp.NVMCTRL.ctrlb().write(|w| w.flmap().bits(0)); // Set the memory flash mapping for AVR128DB28