Custom 3D Printer Firmware for Raspberry Pi Pico with Quadrature Encoders and Advanced Motion Control

This 3D Printer Firmware implements precise multi-axis motion control for my custom built 3D printer using Raspberry Pi Pico/RP2040, featuring quadrature encoder feedback, Bresenham-based path planning, cascaded PID control, and robust configuration storage using LittleFS. Designed for PlatformIO with modular architecture and real-time performance.

Installation Guide
Building the Firmware
Flashing to Raspberry Pi Pico
Hardware Configuration
Core System Architecture
Advanced Configuration
Troubleshooting
Customization for Other Boards

Installation Guide

Prerequisites

PlatformIO Core (VSCode extension or standalone)
Python 3.7+
Git for version control

Repository Setup

git clone https://github.com/Manish-git-tech/3d_printer_firmware_2.git
cd 3d_printer_firmware_2

PlatformIO Configuration

Install dependencies:

pio pkg install

Configure board in platformio.ini:

[env:pico]
platform = raspberrypi
board = pico
framework = arduino

File Structure

src/
├── comms/              # G-code parsing and serial communication
│   ├── comms.cpp       # Command state machine
│   └── comms_parser.h  # G-code syntax definitions
├── motion/             # Motor control and feedback
│   ├── encoder.cpp     # Quadrature decoding
│   └── pid_control.cpp # Cascaded PID implementation
├── path_planning/      # Motion algorithms
│   └── bresenham.cpp   # Coordinated movement
├── config/             # Hardware parameters
│   ├── pins.h          # GPIO mappings
│   └── motion_params.h # Kinematic settings
└── main.cpp            # Firmware entry point

Building the Firmware

Compilation Commands

# Build for Raspberry Pi Pico
pio run -e pico

# Build for ESP8266 (WiFi module)
pio run -e esp8266

# Clean build artifacts
pio run -t clean

Build Flags

Environment Variable	Description
`ENABLE_DEBUG_LOG`	Verbose serial output
`FORCE_EEPROM_RESET`	Clear stored settings

Flashing to Raspberry Pi Pico

Method 1: PlatformIO Upload

pio run -e pico -t upload

Method 2: Manual UF2 Installation

Hold BOOTSEL button while connecting USB
Copy .pio/build/pico/firmware.uf2 to RPI-RP2 drive
Wait for automatic reboot

Required Components

Raspberry Pi Pico (Main Controller)
ESP8266 (WiFi Communication)
MX1508 Motor Drivers (2 per axis)
DC Motors with Quadrature Encoders
24V Power Supply

Pin Mapping Example (`config/pins.h`)

// X-axis Configuration
#define X_ENC_A 2    // Encoder Phase A
#define X_ENC_B 3    // Encoder Phase B  
#define X_MOT_IN1 4  // MX1508 Direction 1
#define X_MOT_IN2 5  // MX1508 Direction 2

Encoder Specifications

Axis	Slits/mm	CPR	Maximum RPM
X	120	480	300
Y	150	600	250
Z	200	800	150

Core System Architecture

1. Quadrature Encoder Handling

Implementation: motion/encoder.cpp

Uses pin change interrupts for real-time decoding

4x counting mode with state transition table:

const int8_t ENCODER_STATES[] = {0,-1,1,0,1,0,0,-1,-1,0,0,1,0,1,-1,0};

Velocity calculation via position differentiation:

float getVelocity() {
  return (current_pos - last_pos) / (micros() - last_time) * 1e6;
}

2. Bresenham Algorithm Implementation

Implementation: path_planning/bresenham.cpp

Coordinated multi-axis movement

Error accumulation for step synchronization:

void BresenhamPlanner::planMove(int32_t target[]) {
  steps[X] = abs(target[X] - current[X]);
  steps[Y] = abs(target[Y] - current[Y]);
  
  err = steps[X] - steps[Y];
  
  while(current != target) {
    if(err * 2 >= -steps[Y]) {
      err -= steps[Y];
      current[X] += x_dir;
    }
    if(err * 2

Motion Parameters (`config/motion_params.h`)

// X-axis Settings
constexpr uint16_t X_STEPS_PER_MM = 80;
constexpr float X_MAX_ACCEL = 1500.0f; // mm/s²
constexpr float X_JERK = 20.0f; // mm/s

// PID Defaults
constexpr float DEFAULT_KP = 10.0f;
constexpr float DEFAULT_KI = 0.05f;

Serial Communication Protocol

Command	Parameters	Description
G0	X Y Z F	Linear move
G1	X Y Z E F	Linear move with extrusion
M2000	Pid values	change and save pid values in EEPROM
M2001	--	Load pid values

Troubleshooting

Common Issues

Symptom	Likely Cause	Solution
Position drift	Encoder noise	Add 0.1μF capacitors to encoder inputs
Motor stalling	PWM below 47%	Increase minimum power in `motor_control.cpp`
EEPROM corruption	Improper shutdown	Implement atomic writes with checksums

Diagnostic Commands

# Report encoder counts
M119

# Dump EEPROM contents
M503

# Test axis movement
G0 X100 F500

Customization for Other Boards

Adapting for ESP32

Modify platformio.ini:

[env:esp32]
platform = espressif32
board = esp32dev
framework = arduino

Update pin mappings in config/pins.h

Supporting New Encoders

Implement encoder interface:

class CustomEncoder : public EncoderBase {
  public:
    int32_t read() override;
    void init() override;
};

Encoder* x_encoder = new CustomEncoder(X_ENC_A, X_ENC_B);

MIT License - Free for personal and commercial use

Special Thanks:

Marlin Firmware Team for motion control foundations
PlatformIO for build system
Raspberry Pi Foundation for Pico SDK

Note: Always verify electrical connections before powering on the system. Incorrect wiring may damage components.

Manish-git-tech/3d_printer_firmware_2