I think I've achieved horizontal playfield scrolling with via bus stuffing and the Strong-ARM driver. If you have a harmony cartridge please try it out.
Cherry-Tree-Scroll3.bin 32KB 41 downloads - 1/25/18 Optimized driver with lookup table and self modifying ARM code, fixed graphic data glitch
Cherry-Tree-Scroll2.bin 32KB 40 downloads - 1/6/18 disables VBLANK during stuff detection because collision registers won't be set if VBLANK is enabled.
Cherry-Tree-Scroll.bin 32KB 39 downloads
Not supported in emulators yet. Here's what it looks like for those who don't have a harmony cart.
Edited by ZackAttack, Thu Jan 25, 2018 1:08 AM.