Rev 1.0 rendered top view

This repository contains the complete Altium Designer project files, schematics, and manufacturing outputs for the Atlas Tracking Unit (ATU).

ATU is a custom-engineered, PCB designed to interface directly with a vehicle's CAN bus network, process data via an on-board STM32 MCU, and provide physical interfaces for cellular (LTE), GNSS, and local SD storage. It features a robust, custom power tree designed to withstand unregulated automotive electrical environments (4V-14V).

1. Clone or Download this repository.
2. Launch Altium Designer.
3. Open the project file:
   Atlas_Telemetry_Unit.PrjPcb

The hardware is centered around the STM32L476 MCU, which physically routes and manages all peripherals:

• CAN Interface: Routed through a dedicated CAN transceiver with hardware ESD protection.
• Modem Interface: Connected to the SIM7600G-H via high-speed UART, utilizing a 1.8V to 3.3V bidirectional logic level shifter.
• Storage Interface: Hardware routing to a Micro-SD card slot for local data access.
• Debug/Config: Direct USB 2.0 lines routed to the MCU, alongside a standard SWD programming header.

• Microcontroller: STM32L476RGT6 (Ultra-low-power ARM Cortex-M4)
• Cellular/GNSS Modem: SIM7600G-H (Global LTE CAT4 with GNSS support)
• CAN Transceiver: TJA1050 (protected by PESD1CAN-UX TVS diode)
• Logic Level Translation: TXS0108ERGYR (1.8V to 3.3V logic shifting)
• Storage: Standard Micro-SD card slot

The board is designed to handle harsh vehicle transients and seamlessly switch between vehicle power and standard USB power for bench testing.

• Inputs: 4V-14V DC Input (Vehicle) & 5V USB Type-C.
• Protection: MOSFET-based Reverse Polarity Protection (FDD6637) and TVS Over-Voltage Protection (SMCJ14A).
• Power Multiplexer: TPS2121RUXR (Prioritizes DC IN over USB, limits current to 2.7A).
• Main Buck Converter: TPS563200 (Steps VIN down to a stable 3.8V @ 2A for the high-current GSM Module).
• LDO: ME6211C33M5G-N (3.8V to 3.3V for clean MCU logic).

Rev 1.0 manufactured prototype with 3D printed enclosure

• Dimensions: 100 mm x 70 mm
• Layer Count: 4 Layers (Signal / Solid GND / Split Power / Signal)
• Material: FR-4 (JLC04161H-7628 stackup)
• Routing: 50Ω single-ended impedance control for RF traces (LTE MAIN, LTE AUX, GNSS).

• Schematics: 01_Schematics/
• PCB Layout: 02_Layout/
• Libraries: 03_Libraries/ (Local .SchLib & .PcbLib included)
• Manufacturing: releases/ (Gerbers & BOM)

The Rev 1.0 board has been validated and successfully tested in real-vehicle scenarios, but the following physical hardware issues were identified and should be corrected in future revisions:

1. Silkscreen Error: The silkscreen labels for the crystal oscillators Y1 and Y2 are physically swapped on the board.
2. CAN RX/TX Routing: The RX and TX traces between the TJA1050 CAN transceiver and the STM32 MCU were routed in reverse.
3. Logic Shifter Limitation: The TXS0108ERGYR bidirectional level shifter proved to be a sub-optimal hardware choice for high-speed UART traces between the MCU and the SIM7600. It lacks reliability at baud rates exceeding 115200 bps. Future revisions should consider a direction-controlled level shifter or a dedicated UART isolator.

This project is open-source and licensed under the MIT License.