85 lines
4.3 KiB
Markdown
85 lines
4.3 KiB
Markdown
# Raspberry Pi 1 Bare-Metal Synthesizer
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This project turns an original Raspberry Pi (Model 1 B/B+, Zero, or Zero W) into an instant-on, single-voice synthesizer that runs without any operating system (bare metal).
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It boots in under two seconds and produces sound and graphics with minimal external components.
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## Features
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- **Instant-On**: Boots directly into the synth application in ~1-2 seconds.
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- **Audio Output**: Generates a sawtooth waveform on the 3.5mm composite audio jack.
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- **Video Output**: Displays a simple amplitude visualizer on the composite video output.
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- **Looped Melody**: Plays a pre-programmed random melody, no input required.
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## Requirements
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### Hardware
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- **Raspberry Pi**: Model 1 (A, B, B+), Pi Zero, or Pi Zero W. This code is for the **BCM2835** SoC and will **not** work on Pi 2, 3, 4, or 5.
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- **SD Card**: A microSD or standard SD card (depending on your Pi model), 1GB is more than enough.
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- **Power Supply**: A standard 5V micro-USB power supply.
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- **Audio Cable**: A 3.5mm audio cable to connect to headphones or a speaker.
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### Software
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- **Distrobox**: Required for the automated setup script. It works on most Linux distributions and is pre-installed on systems like Fedora Silverblue/Kinoite and Bazzite.
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- The provided scripts handle all other dependencies.
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## Quick Start (Recommended)
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This project includes scripts to automate the entire setup and deployment process.
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### 1. Set Up the Development Environment (One-Time Setup)
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The `setup-dev-env.sh` script creates a self-contained environment with all the necessary build tools, without altering your host operating system.
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```sh
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./setup-dev-env.sh
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```
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### 2. Build and Deploy to SD Card
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Insert a FAT32-formatted SD card so that it is mounted by your system. The `deploy.sh` script will then build the kernel, download the necessary firmware, and interactively ask you which device to deploy to.
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Run the script with `sudo` because it needs permission to unmount the drive when it's finished.
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```sh
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sudo ./deploy.sh
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```
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Follow the on-screen prompts to select your SD card. The script handles the rest.
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## How the Automation Works
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- **`setup-dev-env.sh`**: This script uses Distrobox to create a lightweight Ubuntu container named `pi-synth-dev`. Inside this container, it installs the `make` and `gcc-arm-none-eabi` toolchain required for cross-compiling. This isolates dependencies and keeps your host system clean.
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- **`deploy.sh`**: This script orchestrates the entire build and deployment process from your host machine:
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1. **Builds the Kernel**: It automatically enters the `pi-synth-dev` container to run `build.sh`, which compiles the source code into `kernel.img`.
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2. **Fetches Firmware**: It checks for `bootcode.bin` and `start.elf`. If they are missing, it downloads them from the official Raspberry Pi firmware repository.
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3. **Finds the SD Card**: It scans for *mounted* removable drives and presents an interactive menu for you to choose the correct SD card partition.
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4. **Copies Files**: It copies `kernel.img`, `bootcode.bin`, and `start.elf` to the selected SD card.
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5. **Unmounts**: It safely unmounts the SD card, making it ready for use in the Raspberry Pi.
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## Manual Alternative
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If you prefer not to use the scripts, you can perform the steps manually.
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1. **Install Toolchain**: Install `gcc-arm-none-eabi` and `make` on your system.
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2. **Get Firmware**: Download `bootcode.bin` and `start.elf` from the official Raspberry Pi firmware repository.
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3. **Build**: Run `make` to compile `kernel.img`.
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4. **Deploy**: Copy `kernel.img`, `bootcode.bin`, and `start.elf` to the root of a FAT32-formatted SD card.
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## Hardware Connections
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1. **SD Card**: Insert the prepared SD card into your Raspberry Pi.
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2. **Audio**: Connect headphones or a speaker to the 3.5mm audio jack.
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3. **Video (Optional)**: Connect a composite video cable from the RCA jack (on Model B) or the 3.5mm jack (on later models) to a compatible display.
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4. **Power**: Connect the 5V micro-USB power supply. The Pi will boot immediately.
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## Usage
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Once powered on, the synthesizer will automatically start playing a random melody loop. The composite video output will show a simple red bar that visualizes the audio amplitude.
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There is no user input required for this version of the code.
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---
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*This project is for educational purposes and demonstrates low-level hardware control on the BCM2835 SoC.* |