PiLibSDK - Raspberry Pi bare-metal SDK library

PiLibSDK is a bare-metal library for Raspberry Pi modules. "Bare-metal" means that programs run directly on the hardware without an operating system, they are not controlled by the operating system, and they have full access to the hardware. Raspberry Pi modules can thus be used in a similar way to microchips. Another advantage is that the device is fully operational within 3 seconds of powering on. Currently, the Raspberry Zero 1, Zero 2 W, Pi 2, and Pi 3 modules are supported. Support for the Pi 4 and Pi 5 modules is very limited, and they will likely not be supported in the future either, as their benefits for bare-metal use are minimal.

Sample programs have been prepared for the BarePi modular microchip kit (links: www, GitHub). Of course, you don’t have to follow the hardware wiring exactly, but this is the most common pin-to-signal mapping. The main device is the ZeroTiny game console, which corresponds to the configuration of the "Zero," "Base," and "KeyPad" modules.

An LCD SPI display with a resolution of 320x240 pixels and ST7789 controller can also be connected to the device. The wiring corresponds to the "LCD320x240" module from the BarePi kit. The software library is designed so that when it detects the connection of the LCD320x240 module, it activates the SPI output to the display and sends the image to this LCD display as well. Detection is performed using a 10K resistor connected between the DC and CS pins. If you want to be able to disable the LCD display output on the target device, you can do so using a switch that connects this 10K resistor. Detection occurs when the application or loader starts - so after changing the switch, you must terminate or start the program or loader. Disabling the output to the LCD display ensures faster program execution, as sending data to the LCD display heavily loads the program.

Although the LCD SPI display has a resolution of only 320x240 pixels, it is possible to use programs with a resolution of 640x480 pixels. The driver automatically scales the image down to the target size. If you need to display details on the LCD display that would be lost due to the scaling, you can do so by pressing Alt+[A] - the "Insert" function is used here to mean "Zoom". When you press the keys, the LCD display will sequentially show each of the four quadrants of the image in full resolution; pressing the keys a fifth time restores the full scaled-down image.

If you do not need the HDMI output while using the LCD display, disconnect the monitor cable. This will result in a significant reduction in current consumption (from approximately 400 mA to 200 mA), which is especially important when running the console on battery power. The system detects whether an HDMI monitor is connected when the program starts - therefore, after disconnecting or connecting an HDMI monitor, you must exit or restart the program or loader. With the Raspberry Zero 1 module, it may be necessary to disconnect and reconnect the power supply to detect the HDMI monitor.

If you connect a DS3231 real-time clock circuit to the device, applications will retrieve the current real-time clock value from it. The I2C EEPROM memory provides the ability to save program configurations.

A boot loader is available for BarePi devices, which allows easy launching of programs from an SD card. The programs are ready for BarePi and ZeroTiny, with Zero 1, Zero 2 32-bit, or Zero 2 64-bit modules. The Zero 1 and Zero 2 modules differ primarily in speed - the Zero 2 is noticeably faster than the Zero 1. The higher speed is due not only to a higher processor frequency but also to a newer architecture. In addition, the Zero 2 module has 4 cores, while the Zero 1 has only one core. Therefore, it is strongly recommended to use the Zero 2 module. Use the Zero 1 module only if you own it and have no better use for it. The Zero 2 module can be operated in 32-bit or 64-bit mode. The compilations are prepared for both modes. From a user’s point of view, there is no noticeable difference between the modes. It is recommended to prefer 64-bit mode, which may be slightly faster in some cases.

The BarePi kit can be controlled using either the "KeyPad" gaming keyboard or the "MiniKey" alphanumeric keyboard. The keys on the "KeyPad" keyboard are also mapped to the keys on the "MiniKey" keyboard. To distinguish between key labels, action keys from the gaming keyboard are listed in square brackets, while character keys are listed without brackets. For example, "[A]" denotes the "A" action key on the gaming keyboard. The meanings of the keys on the gaming keyboard and their mapping to the alphanumeric keyboard are as follows.

Note: A boot loader is not required to run programs. You can run programs directly on the Zero1/Zero2 module itself, without additional hardware or a boot loader. Copy the system files from the Root directory of the corresponding !ZeroTiny* folder to the SD card. You will need the files "bootcode.bin", "config.txt", "fixup.dat", and "start.elf". Copy the program to the Root folder as well, and rename it to KERNEL.IMG. The program will start automatically when power is turned on.

License

All of my source code and data are completely free to use for any purpose. The exception is certain files derived from third-party sources - these are subject to the original author’s license. This includes most fonts, as well as portions of source files taken from the Circle library and Linux code - these sections are marked in the source files.

Most fonts in this library are not my creation. They were downloaded from the internet from unknown sources, with unknown license terms of use. If you want to use only strict licenses, do not use fonts from this library.

Compilation

To compile 32-bit mode, you will need AArch32 GCC (tool name "arm-none-eabi"). Install to C:\ARM_GCC32.

To compile 64-bit mode, you will need AArch64 GCC (tool name "aarch64-none-elf"). Install to C:\ARM_GCC64.

Directories

To prepare the SD card, format it to FAT32, copy the contents of the !BarePi folder to it, as well as one of the !BarePi_* folder (depending on the module type).

ZeroTiny

ZeroTiny is the simplest game console based on the Raspberry Pi Zero 1 or Zero 2 modules. This corresponds to the assembly of the "Zero," "Base," and "KeyPad" modules from the BarePi kit. It is recommended to preferably use the Zero 2 module in 64-bit mode. The Zero 1 module may be noticeably slower in some applications. ZeroTiny features 9 buttons, a stereo PWM audio output, and an HDMI display output. A boot loader is available, allowing for easy program launch from an SD card.

The ZeroTiny is designed in a sandwich-style construction. In my prototype, I connected the Zero module to the motherboard via an 8mm header - primarily to facilitate easy module replacement. If you solder the Zero module to the board using only a pin header, the design will be lower. However, this may make repairs more difficult, such as replacing a button.

Detailed materials for ZeroTiny hardware can be found in the "_devices/BarePi/ZeroTiny" folder.

You can find the compiled sample programs in the "!BarePi*" folders, organized by module type and processor mode.

Sample Applications

BALLOONS - Flying balloons	BIGFACT - Factorial of 123456789!	DRAW - Drawing graphic elements	EARTH - Rotating globe	FLAG - Fluttering flag
FLAG2 - Fluttering custom flag	FOUNTAIN - Draw 3D graph	FRUITY - 130 music loops with MP3 compression	HELLO - Simplest example	HYPNO - hypnotic rotating pattern
LEVMETER - simulation of music spectrum indicator	LINEART - draw line flower	LINES - relaxation line pattern generator	MATRIX - matrix code rain	OSCIL - simulation of oscilloscope signal
PF2027 - Christmas animation	PI - calculating number Pi to 4780 digits	PIXELS - random generation of colored pixels	RAYTRACE - 3D pattern generation by ray tracing method	SPHERES - random spheres
SPOTS - random spots	TWISTER - twisting textured block	WATER - simulation of rippling water surface

ANTS - card game	ATOMS - Game of exploding atoms	EGGS - Logic game as Reversi
FIFTEEN - Logic puzzle game	FLAPPY - Logic game from Sharp MZ800	CHESS - Chess game
INVADERS - Shooting game Space Invaders	LIFE - Cell life simulator	MAZE - Find way out of maze
PACMAN - Action game Pac-Man	PICTOR - Picopad Collector	RAPTOR - Shooting game

I recommend using MP3 files with a constant bitrate. Some older MP3 formats, or MP3s with a variable bitrate, may not allow you to move the playback pointer, or the track may end prematurely before the end. The player only supports short file names - that is, the name of an MP3 file can be up to 8 characters long. If a folder also contains a JPG image with the same name as the MP3, with dimensions of 320x240 pixels, it will be displayed instead of the info page. You can switch between the image and the info using the [X] key. The [B] key plays the current directory starting from the first track. The [A] key starts playback from the current track.

The player comes with a sample set of songs, in the style of various artists, created in Suno AI. In total, there are 248 tracks, containing 13 hours of music. Samples can be downloaded here.

Download samples part 4 (217 MB): styles of Loreena McKennitt, Medieval, Meditation, Metal, Vox Angeli

Download samples part 5 (207 MB): styles of Mixed, Nightwish with Tarja Turunen, Mike Oldfield

EEPROM - View contents of I2C EEPROMs	I2CSCAN - Scan I2C0 and I2C1 bus	LCD - Test LCD SPI display	RTC - Display and set current time, using RTC module	SSD1306 - Test SSD1306 display
TESTLED - Test BarePi bus with TESTLED module

Contents

Intro

License

Compilation

Directories

ZeroTiny

Sample Applications