This is my sdk for usage with slackware on A20 devices like bananapi, cubietruck and olimex-som. For more info see https://github.com/tjohann/a20_sdk .
ATasm is a 6502 command-line cross-assembler that is compatible with the original Mac/65 macro assembler released by OSS software. The aim of ATasm is to provide Atari home-brew coders with a comfortable and powerful toolset.