piOledDriver

GitHub Repo: https://github.com/elicampos/piOledDriver
Branch: master

A simple C++ project demonstrating how to drive an SH1106/SSD1306-like OLED display via SPI and gather CPU usage stats (using mpstat). Designed for a Raspberry Pi 5 or similar Linux SBC with libgpiod for GPIO access.

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Table of Contents

• Overview
• Hardware Requirements
• Software Dependencies
• Project Structure
• Build Instructions
• Usage
• Notes & Caveats
• License

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Overview

1. SPI Communication

   • Leverages /dev/spidev0.0 in write-only mode to send commands/data to the OLED.
   • Uses ioctl() calls to configure SPI mode, speed, and bits per word.

2. OLED Display (SH1106)

   • Contains a 5×7 font array and functions to draw text, clear the screen, and perform initialization steps (contrast, orientation, charge pump, etc.).
   • The display code offsets columns by 2 pixels (standard for many SH1106 modules).

3. CPU Stats

   • Runs mpstat -P ALL 1 1 to output CPU usage into a text file, then parses the “Average: all” line to extract user, system, irq, and idle usage.

4. GPIO Control via libgpiod

   • Uses gpiod_chip_open("/dev/gpiochip0") to request two output lines:
     • DC (Data/Command): Typically GPIO9 on Raspberry Pi 5.
     • RESET: Typically GPIO25 on Raspberry Pi 5.

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Hardware Requirements

1. Raspberry Pi 5 (or similar board) with:
   • SPI enabled via raspi-config.
   • Accessible /dev/spidev0.0 and /dev/gpiochip0.
2. SH1106-based 128×64 OLED wired to:
   • SPI: CE0, SCLK (GPIO11), MOSI (GPIO10)
   • DC: GPIO9 (or your chosen pin)
   • RESET: GPIO25 (or your chosen pin)
3. A stable 3.3V (or 5V) supply, depending on your OLED module’s requirements.

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Software Dependencies

• C++17 (or later) compiler (e.g., g++).
• libgpiod (for GPIO line management).
• mpstat (typically in the sysstat package) for CPU usage measurement.
• SPI drivers enabled on the Pi (spidev kernel module).

Install on Debian-based systems (including Raspberry Pi OS):

sudo apt-get update
sudo apt-get install -y gpiod libgpiod-dev sysstat