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40-Setup.md

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Setup

There are not enough GPIO pins nor RAM on a single Pico to handle all the stuff we want, so a dual or even triple Pico setup seems to be a possible way to go.

Idea #1: Main with VGA and sound, I/O on another

  • Pico #1: Main

    • Base model (or an extended one with 8 or 16 Mb of flash memory)
    • REPL / Shell / Editor
    • VGA framebuffer
    • Sound hardware

  • Pico #2: I/O

    • Either base model or W if Wi-Fi needed
    • USB 1.1 via multi-port hub for keyboard, mouse and gamepads
    • SD Card
    • RTC
    • Wi-Fi
    • Ethernet

  • Link with other Pico

    • See below for possible hardware solutions
    • API to make requests from main Pico to I/O Pico

Pros:

  • “Real time” access to VGA & sound

Cons:

  • Limited size of framebuffer or code, need to find a trade-off between the 2
  • I/O will be constrained by link speed

Idea #2: Main with I/O and VGA on the other

The main resource hog is VGA, so we could dedicate a Pico to it, and using it as a “graphical co-processor” from the main Pico.

  • Pico #1: Main

    • Either base model or W if Wi-Fi needed
    • REPL / Shell / Editor
    • Sound hardware
    • USB 1.1 via multi-port hub
    • SD Card
    • RTC
    • Wi-Fi
    • Ethernet

  • Pico #2: VGA

    • Base model

  • Link between the Picos

    • See below for possible hardware solutions

  • API to send requests from main Pico to VGA Pico

    • Graphic primitives (put pixel, line, rectangle, circle & al., see HAGL)
    • Font uploading and text drawing
    • Assets uploading (images and sprites)
    • Blitting primitives (display image portion, display or move sprite, ...)
    • Tilemap support?
    • Scrolling support?

Pros:

  • No trade-off needed anymore for program size on main Pico
  • Framebuffer could be bigger, even more than 64K
  • Better stabillity of VGA can be expected
  • I/O, notably file access will be faster
  • This VGA implementation could be used in other projects

Cons:

  • Link speed will limit control on the VGA part
  • I/O, notably Wi-Fi, will use RAM & Flash space on main Pico
  • VGA API programming will be more complex on either side
  • It's essentially reproducing an I²C/SPI LCD panel with VGA output

Idea #3: Main, I/O & VGA

  • Pico #1: Main

    • Base model (or an extended one with 8 or 16 Mb of flash memory)
    • REPL / Shell / Editor

  • Pico #2: I/O

    • Either base model or W if Wi-Fi needed
    • USB 1.1 via multi-port hub for keyboard, mouse and gamepads
    • SD Card
    • RTC
    • Wi-Fi
    • Ethernet

  • Pico #3: VGA

    • See VGA of idea #2

Pros:

  • See idea #2 except I/O speed
  • Main Pico is quite entirely free to handle whatever we want

Cons:

  • See idea #2 except Wi-Fi resource usage

Communication between the Picos