PREN PCB

PREN Puzzle Robot - TinyK22 Controller

This repository contains the control software for the PREN Puzzle Robot (Lucerne University of Applied Sciences and Arts). The system is based on an NXP Kinetis TinyK22 (MK22FN512VLH12) and controls 3 stepper motors, one servo, and a vacuum pump to sort puzzle pieces.

The system utilizes a Dual-UART architecture and a specialized Homing System for precision and automatic field calibration.

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🔌 Hardware & Pin Mapping

The system utilizes both header rows (J4 and J3) of the TinyK22 as the primary header's GPIOs are fully utilized.

Pin Assignment Table

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TMC2209 Driver Wiring

A TMC2209 driver is used for each motor (X, Y, Rotation).

• EN (Enable): Connected to TinyK22 PTB3 pin (Active-Low). Allows de-energizing motors in idle states.
• VIO (Logic): Connected to TinyK22 3.3V.
• GND: Connected to TinyK22 GND.
• VM (Motor Power): Supplied via 24V.

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📡 Dual-UART Communication

The system strictly separates machine communication from human diagnostics.

1. Data Channel (Raspberry Pi)

• Interface: UART 2
• Pins: J4 Pin 9 (RX) & Pin 10 (TX)
• Baudrate: 115200, 8N1
• Protocol: Pipe-separated ASCII commands (move|x=.., pick, place, etc.).

2. Console Channel (Debugging)

• Interface: UART 0
• Pins: PTB16 / PTB17 (Hardwired to Micro-USB Port via OpenSDA).
• Baudrate: 115200, 8N1
• Function: PRINTF output for real-time diagnostics. Can be monitored via PC terminal (e.g., PuTTY, HTerm).

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🚀 Software Architecture

The firmware follows industrial standards with strict separation between Hardware Abstraction (HAL) and logic layers:

• robot_config.h (Central Control): All physical parameters (mm/s, angles, timings) are defined here. The C-Preprocessor converts these into timer delays using Fixed-Point Arithmetic (Q1000), ensuring high precision without resource-intensive floating-point operations.
• motion.c (High-Performance Kinematics): Implements the David Austin Trajectory for smooth acceleration ramps. It uses the PIT Timer (Interrupts) for asynchronous, non-blocking step generation.
• robot_ctrl.c (Non-Blocking State Machine): Manages the overall workflow (Homing -> Idle -> Pick/Place). The CPU utilizes the WFI (Wait For Interrupt) instruction to maximize efficiency while waiting for hardware events.
• periphery.c (HAL): Encapsulates pin logic and implements 3ms Software Debouncing for all mechanical switches to eliminate vibration-induced false triggers.

Safety & Calibration Concept

1. E-Stop: A hardware-monitored state immediately halts all timer ramps and releases the vacuum.
2. Homing Switches (X_0, Y_0): Used to establish a precise machine origin.
3. Reset Behavior: Upon receiving a "reset" command, the robot moves back to coordinates (0,0,0) before de-energizing motors and entering the "Wait for Start" state.

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🛠️ Commands (Raspberry Pi -> TinyK22)

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Author: Jan (PREN Team)
Hardware: TinyK22 (NXP MK22FN512VLH12)
Date: 2026