LED7SEG02 - Project Documentation

Documentation for LED7SEG02 project - 7-segment display with WS2815 addressable RGB LEDs and RS485 communication.

Project Overview

This project implements control of a 7-segment display consisting of 29 WS2815 RGB LEDs using STM32G031F8Px microcontroller. The display is controlled via RS485 bus using a defined protocol.

Basic Specifications

• MCU: STM32G031F8Px (Cortex-M0+ @ 64MHz)
• LEDs: 29× WS2815 RGB (7 segments × 4 LEDs + 1 decimal point)
• Communication: RS485 @ 921600 baud
• Power: 3.3V (MCU), 12V (LEDs)

Documentation Structure

WS2815_Driver_en.md

Complete WS2815 driver documentation including:

• API reference
• Visual effects library
• Usage examples
• Troubleshooting

Hardware_Configuration_en.md

Hardware configuration and specifications:

• MCU pinout
• Peripheral settings
• Wiring diagram

protocol_en.md

RS485 communication protocol:

• Frame structure
• Command list
• CRC-8 calculation
• Communication examples

firmware_en.md

Firmware documentation:

• Software architecture
• Module descriptions
• Data flow

Quick Start

1. Building the Project

Open project in STM32CubeIDE:

File → Open Projects from File System
→ Import source: LED7SEG02\sw

Build project: Project → Build Project (Ctrl+B)

2. Basic Usage

#include "sw_ws2815.h"
#include "sw_effects.h"

void APP_Init(void) {
    WS2815_Init();
    WS2815_SetBrightness(50);
    Effects_Init();
    RS485_Init();
    Protocol_Init();
    RS485_StartReceive();
}

void APP_Main(void) {
    WS2815_Color_t green = {0, 255, 0};

    // Display digit
    WS2815_DisplayDigit(8, green, 1);
    WS2815_Update();
    while(WS2815_IsBusy());
}

3. Hardware Connection

PA0 (MCU) ──────► DI (WS2815)
GND (MCU) ──────► GND (WS2815)
12V PSU   ──────► +12V (WS2815)

PA2 (MCU) ──────► DI (MAX3485)
PA3 (MCU) ◄────── RO (MAX3485)
PA1 (MCU) ──────► DE/RE (MAX3485)

Project Structure

LED7SEG02/
├── doc/                          # Documentation
│   ├── README.md                 # This file (CZ)
│   ├── README_en.md              # This file (EN)
│   ├── WS2815_Driver.md          # Driver documentation (CZ)
│   ├── WS2815_Driver_en.md       # Driver documentation (EN)
│   ├── Hardware_Configuration.md # Hardware documentation (CZ)
│   ├── Hardware_Configuration_en.md # Hardware documentation (EN)
│   ├── protocol_cz.md            # Protocol (CZ)
│   ├── protocol_en.md            # Protocol (EN)
│   ├── firmware_cz.md            # Firmware (CZ)
│   └── firmware_en.md            # Firmware (EN)
├── hw/                           # Hardware design files
├── sw/                           # Firmware
│   ├── Core/                     # STM32 HAL core
│   ├── Drivers/                  # STM32 HAL drivers
│   ├── src/                      # Application code
│   │   ├── app.c
│   │   └── app.h
│   ├── sw/                       # Custom drivers
│   │   ├── sw_ws2815.c/.h        # WS2815 driver
│   │   ├── sw_rs485.c/.h         # RS485 driver
│   │   └── sw_protocol.c/.h      # Communication protocol
│   └── sw_effects/               # Visual effects
│       ├── sw_effects.c/.h
│       └── README.md
└── app/                          # Python test application
    ├── led7seg_test.py
    └── config.json

Key Features

WS2815 Driver

• Hardware PWM + DMA (no bit-banging)
• 800 kHz bitrate
• Non-blocking operations
• Adjustable brightness (10-254)
• Precise timing (TIM2 @ 64MHz)
• Low CPU usage

Visual Effects

• Rainbow - rainbow color cycle
• Spinning - spinning LED
• Breathing - breathing effect
• Segment Chase - running segments
• Knight Rider - K.I.T.T. effect
• Loading Bar - progress bar
• Rainbow Digit - digit with changing color
• Rainbow Gradient - digit with rainbow gradient

RS485 Communication

• 921600 baud, 8N1
• Hardware RS485 mode (automatic DE control)
• Interrupt-based receive/transmit
• IDLE line detection for frame end
• CRC-8 validation
• Response time < 2ms

Peripheral Configuration

Peripheral	Pin	Function
TIM2_CH1	PA0	WS2815 Data
USART2_TX	PA2	RS485 TX
USART2_RX	PA3	RS485 RX
USART2_DE	PA1	RS485 Direction
GPIO	PA4	Address bit 0
GPIO	PA12	Address bit 1
GPIO	PB0	Address bit 2
GPIO	PA11	Address bit 3

Segment Mapping

    aaaa
   f    b
   f    b
    gggg
   e    c
   e    c
    dddd  dp

Segment	Index	LED positions
a	0	0-3
b	1	4-7
c	2	8-11
d	3	12-15
e	4	16-19
f	5	20-23
g	6	24-27
dp	7	28

API Quick Reference

Initialization

WS2815_Init();                      // Initialize driver
WS2815_SetBrightness(brightness);   // Set brightness (10-254)
Effects_Init();                     // Initialize effects

Display Control

WS2815_DisplayDigit(digit, color, show_dp);  // Display digit 0-9
WS2815_SetSegment(segment, color);           // Set segment
WS2815_SetLED(index, color);                 // Set LED
WS2815_Clear();                              // Turn off all LEDs

Update

WS2815_Update();                    // Send data (non-blocking)
WS2815_IsBusy();                    // Check if busy

Effects

Effects_Rainbow(step);                          // Rainbow effect
Effects_RainbowDigit(digit, show_dp, step);     // Rainbow on digit
Effects_Breathing(step, color);                 // Breathing
Effects_KnightRider(pos, color);                // K.I.T.T.

Troubleshooting

LEDs not lighting

1. Check 12V power supply
2. Check PA0 → DI wiring
3. Check common ground
4. Verify DMA buffer (WS2815_IsBusy)

RS485 not communicating

1. Check baud rate (921600)
2. Verify A/B wire connections
3. Check BCD switch address
4. Measure DE pin activity

Wrong colors

• Check brightness setting (range 10-254)
• Check power supply voltage (min 11V)

Version History

v1.0 (2026-02)

• WS2815 driver implementation
• RS485 communication with protocol
• Visual effects library
• Documentation

License and Author

• Project: LED7SEG02
• Author: Richard Roztocil
• Date: February 2026

References

• WS2815 Datasheet
• STM32G031 Datasheet
• MAX3485 Datasheet