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ERROR: type should be string, got " https://github.com/lupyuen/pinetime-rust-mynewt/blob/master/rust/app/src/chip8.rs#L19-L37\n\nWhy did we allocate 8 bits per pixel in SCREEN_BUFFER?\n\nSo that we can implement interesting colour effects. (We'll cover this later) We actually update SCREEN_BUFFER with a greyscale colour like this...\n\nunsafe { SCREEN_BUFFER [ i ] = if color { if self. is_interactive { 255 } else { 200 } } else { if self. is_interactive { 127 } else { 0 } } };\n\nFrom https://github.com/lupyuen/pinetime-rust-mynewt/blob/master/rust/app/src/chip8.rs#L169-L198\n\nSomething seems to be missing... vram_set updates a screen buffer in memory... But we haven't actually updated the PineTime display!\n\nvram_set is called every time the Emulator paints a pixel. Instead of refreshing the PineTime display pixel by pixel, we update the display by Sprite instead.\n\nWhat's a Sprite?\n\nNo not the lemon-lime drink... It's the graphic that moves around in a game. In the Blinky / Pac-Man game, Pac-Man and the Ghosts are rendered as Sprites.\n\nHow do we know when a Sprite has been drawn?\n\nWe detect that in the sched function, where we update the PineTime display too.\n\nHow does CHIP-8 run game programs and render Sprites?\n\nThink of CHIP-8 as an old-style home computer from the 1980s. It executes simple 8-bit Instructions (Opcodes), reading and writing data to CPU registers and RAM.\n\nCHIP-8 has a unique Instruction that's not found in computers from the 1980s... An Instruction that renders Sprites. Since CHIP-8 renders Sprites as an CHIP-8 Instruction, we should update the PineTime screen only when the CHIP-8 Instruction has completed.\n\nThe CHIP-8 Emulator provides a convenient hook for that... It calls sched after executing every CHIP-8 Instruction...\n\nimpl libchip8 :: Hardware for Hardware { fn sched ( & mut self ) - > bool { if self. update_left = = 0 & & self. update_right = = 0 & & self. update_top = = 0 & & self. update_bottom = = 0 { return false ; } if! self. is_interactive { return false ; } if! self. is_checking_input { return false ; } self. is_checking_input = false ; unsafe { hal_watchdog_tickle () }; unsafe { os :: os_time_delay ( 1 ) }; render_region ( self. update_left, self. update_top, self. update_right, self. update_bottom ); self. update_left = 0 ; self. update_top = 0 ; self. update_right = 0 ; self. update_bottom = 0 ; false }\n\nFrom https://github.com/lupyuen/pinetime-rust-mynewt/blob/master/rust/app/src/chip8.rs#L231-L268\n\nInstead of updating the entire PineTime display, we update only the rectangular portion that has been changed, by calling render_region.\n\n(Recall that screen updates are tracked by vram_set )\n\nUpdating the PineTime display really slows down the CHIP-8 Emulator, so we defer all display updates until absolutely necessary.\n\nWhen is it absolutely necessary to update the PineTime display?\n\nThat's when the game has rendered something and is checking whether the player has pressed any buttons\n\nThus we have these conditions to defer the PineTime display updates in sched...\n\nif! self. is_interactive { return false ; } if! self. is_checking_input { return false ; } self. is_checking_input = false ;\n\nFrom https://github.com/lupyuen/pinetime-rust-mynewt/blob/master/rust/app/src/chip8.rs#L231-L268\n\nis_interactive and is_checking_input are flags set in the key function, which is called whenever the CHIP-8 Emulator is checking for button presses.\n\nThese simple conditions for defering the PineTime rendering are extremely effective. They make the PineTime CHIP-8 Emulator refresh some screens quicker than other versions of the CHIP-8 Emulator.\n\n(Compare the loading screen for Blinky on PineTime vs other platforms)\n"