Neotron Pico BIOS

This is the Neotron BIOS for the Neotron Pico board.

Compatibility

This BIOS will run on the Neotron Pico v0.5.0. Other boards based around the Raspberry Pi Pico could be supported with just a minor change to the pin configurations.

Features

The Neotron Pico offers:

• Dual Cortex-M0+ clocked at 133 MHz
• 256 KiB RAM
• 2048 KiB Flash
• SD/MMC Slot
• 4096-colour VGA output
• Stereo 16-bit 48kHz audio
• Four Neotron expansion slots
• A dedicated Board Management Controller, offering:
  • Dual PS/2 ports
  • 5-wire TTL UART
  • Power/reset control

Currently the BIOS only uses a single core, and starts the OS on the same core. Later versions may move some functionality onto the second core (e.g. screen updates) for performance reasons.

Programming

The Neotron BIOS uses the defmt crate to provide structured logging over the SWD interface. The easiest way to flash and debug your Neotron Pico BIOS is with a second Raspberry Pi Pico.

1. Connect your Debugger Pico to the Neotron Pico:

   • connect Pin 3 on the Debugger Pico to GND on the Neotron Pico
   • connect Pin 4 on the Debugger Pico to SWCLK on the Neotron Pico
   • connect Pin 5 on the Debugger Pico to SWDIO on the Neotron Pico
   • connect USB on the Debugger Pico to your PC

2. Flash your Debugger Pico with https://github.com/majbthrd/DapperMime firmware (e.g. by copying the UF2 file to the USB Mass Storage device)

3. On your PC, install probe-rs, the programming tool from Ferrous System's Knurling Project.

user@host ~ $ cargo install probe-rs

4. Power on your Neotron Pico.

5. Build the Neotron OS

We use the "neotron-os-pico.ld" linker script to link it at 0x1002_0000.

user@host ~/neotron-os $ cargo build --release
user@host ~/neotron-os $ arm-none-eabi-objcopy -O binary ./target/thumbv6m-none-eabi/release/flash1002 ../neotron-pico-bios/src/flash1002.bin

6. Build and load the Neotron BIOS, and view the debug output stream, with cargo run --release:

user@host ~/neotron-pico-bios $ DEFMT_LOG=debug cargo run --release
   Compiling neotron-pico-bios v0.1.0 (/home/jonathan/Documents/neotron/neotron-pico-bios)
    Finished release [optimized + debuginfo] target(s) in 0.76s
     Running `probe-run-rp --chip RP2040 target/thumbv6m-none-eabi/release/neotron-pico-bios`
(HOST) INFO  flashing program (7.30 KiB)
(HOST) INFO  success!
────────────────────────────────────────────────────────────────────────────────
 INFO  Neotron BIOS starting...
└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:79
 INFO  Clocks OK
└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:102
 INFO  Pins OK
└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:121
 DEBUG Loop...
└─ neotron_pico_bios::__cortex_m_rt_main @ src/main.rs:128

You should see your Neotron Pico boot, both over RTT in the probe-run output, and also on the VGA output.

Changelog

See CHANGELOG.md

Licence

Neotron-Pico-BIOS Copyright (c) Jonathan 'theJPster' Pallant and the Neotron Developers, 2021

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.

See the full text in LICENSE.txt. Broadly, we (the developers) interpret this to mean (and note that we are not lawyers and this is not legal advice) that if you give someone a Neotron Pico, you must also give them one of:

• Complete and corresponding source code (e.g. as a link to your own on-line Git repo) for any GPL components (e.g. the BIOS and the OS), as supplied on the Neotron Pico.
• A written offer to provide complete and corresponding source code on request.

If you are not offering Neotron Pico commercially (i.e. you are not selling the board for commercial gain), and you are using an unmodified upstream version of the source code, then the third option is to give them:

• A link to the tag/commit-hash on the relevant official Neotron Github repositories - https://github.com/Neotron-Compute/Neotron-Pico-BIOS and https://github.com/Neotron-Compute/Neotron-OS.

This is to ensure everyone always has the freedom to access the source code in their Neotron Pico.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be licensed as above, without any additional terms or conditions.