PIF

PIF (Platform-independent framework) is a portable C framework for embedded systems.

It helps you keep business logic and reusable modules independent from MCU/board-specific code.

TL;DR

• Keep platform code thin.
• Put reusable logic in PIF modules.
• Connect both sides with sig*, act*, and evt* callbacks.
• Drive periodic signals (for example 1 ms tick) and run tasks in your main loop.

5-Minute Quick Start

1. Add PIF to your build

Include these directories in your project:

• include/
• source/

2. Create your config header

Start from include/pif_conf_temp.h and create pif_conf.h in your include path.

Enable only the macros you need for your target.

3. Implement platform hooks

Provide platform-specific functions used by selected modules, such as:

• high-resolution timer callback
• GPIO access callbacks
• communication transport callbacks (UART/SPI/I2C, etc.)

4. Initialize core

Initialize PIF during startup (before entering the main loop):

#include "core/pif.h"

static uint32_t platform_timer1us(void)
{
    // Return current 1 us tick from your platform.
    return 0;
}

void app_init(void)
{
    if (!pif_Init(platform_timer1us)) {
        // Handle initialization failure
        while (1) {}
    }
}

5. Drive periodic signals and tasks

Feed the framework tick signal and execute module tasks:

• call pif_sigTimer1ms() from your 1 ms timer/ISR context (or equivalent timing path)
• run enabled module task handlers from your main loop

Build and Integration Examples

This repository does not include a single official build script because integration is usually done from your firmware project.

GCC (manual compile) example

Use this when you want a quick local compile test:

gcc -std=c11 -Iinclude -c source/core/pif.c -o build/pif.o

To compile with more modules, add additional source files from source/:

gcc -std=c11 -Iinclude \
  -c source/core/pif.c \
  -c source/core/pif_task.c \
  -c source/storage/pif_storage.c

CMake integration example

In your firmware project CMakeLists.txt, add PIF as a library:

cmake_minimum_required(VERSION 3.16)
project(my_firmware C)

set(PIF_ROOT ${CMAKE_CURRENT_LIST_DIR}/third_party/pif)

file(GLOB_RECURSE PIF_SOURCES
    ${PIF_ROOT}/source/*.c
)

add_library(pif STATIC ${PIF_SOURCES})
target_include_directories(pif PUBLIC
    ${PIF_ROOT}/include
)

# Your target
add_executable(app src/main.c)
target_link_libraries(app PRIVATE pif)

If you want faster build times, replace GLOB_RECURSE with an explicit source list for only the modules you use.

Integration Model

PIF sits between platform code and application code.

1. Platform -> PIF: sig* functions (signals/ticks/inputs).
2. PIF -> Platform: callback pointers.
3. Application -> PIF: public API calls.
4. PIF -> Application: evt* callbacks.

Callback naming conventions:

• act*: PIF requests an action from platform/app code.
• evt*: PIF notifies an event.

Project Layout

• include/: public headers grouped by domain
• source/: implementation files grouped by domain

Representative domains:

• core, communication, protocol, sensor, input, storage
• display, motor, sound, gps, filter, interpreter
• markup, rc, osd, actulator

Coding Conventions Used in PIF

Since C has no built-in member visibility, PIF uses naming rules:

• __name: private/internal field (do not access outside owner module)
• _name: externally read-only field (do not modify directly)

Example Project

Working example:

• https://github.com/SlowlyBarefoot/pif-example

Upstream References and Credits

Some modules were influenced by these projects.

Interpreter

• basic: https://github.com/jwillia3/BASIC (Jerry Williams Jr)

Protocol

• ibus: https://github.com/bmelink/IBusBM
• msp: https://github.com/multiwii/baseflight
• sbus: https://github.com/zendes/SBUS
• sumd: https://github.com/Benoit3/Sumd-for-Arduino
• spektrum: https://github.com/SpektrumRC/SRXL2

Sensor

• bmp280: https://github.com/MartinL1/BMP280_DEV
• bmp280 reference: https://github.com/multiwii/baseflight

Sound

• buzzer: https://github.com/multiwii/baseflight

License

See LICENSE.