Hello World no-OS Example Project

See projects/hello_world (doxygen) for the Doxygen documentation.

Overview

This is the simplest possible no-OS project: it initializes the board's UART peripheral and prints a "Hello World" counter message over the serial port once per second. It is intended as a quick-start template for engineers who are new to no-OS and want to understand how to build, flash, and run a bare-metal embedded application on a Xilinx board.

What it demonstrates:

  • The no-OS peripheral descriptor pattern (no_os_uart_init / no_os_uart_remove)

  • The no-OS logging macros (pr_info, pr_err, ...)

  • The no-OS delay API (no_os_mdelay)

  • Proper error handling (checking return values, cleanup on failure)

No-OS Supported Examples

This project is organized around the no-OS variant based build flow. Selecting a variant at build time (--variant <name>) chooses which application is compiled. The platform main() is a thin dispatcher that calls example_main(), provided by the selected example. Platform-specific init parameters are in src/platform.

Basic Example

Initializes the board's UART peripheral and prints a "Hello World" counter message over the serial port once per second. No external hardware is required beyond the board itself.

This example is built by selecting the basic variant (see the Build Command section below).

No-OS Supported Platforms

Xilinx

Used Hardware

  • Any Xilinx FPGA carrier board that exposes a PS UART (ZedBoard, ZC706, ZCU102, Cora Z7, and others). No eval board is required.

Connections

No external hardware connections are required beyond the carrier board's USB cable. The application uses only the ARM Processing System (PS) and its built-in UART — no custom PL logic is needed. Any XSA that targets your board will work, even one borrowed from a different no-OS or HDL project.

The UART console appears on the board's USB-UART adapter at 115200 baud, 8N1, no flow control:

  • Linux: /dev/ttyUSB0 (ZedBoard/Cora Z7) or /dev/ttyUSB1 (ZCU102)

  • Windows: a COM port listed in Device Manager under Ports (COM & LPT)

  • macOS: /dev/tty.usbserial-*

Build Command

The Xilinx platform uses the CMake/Ninja build system via the no_os_build.py helper script. Available variants: basic. Available boards: zed.

For toolchain setup and prerequisites, see the Xilinx CMake build guide.

# source the Vitis environment (adjust path to your Vitis install)
source /path/to/Vitis/2025.1/settings64.sh
# PowerShell (Windows) equivalent:
#   & "<path\to\Vitis\2025.1\settings64.bat"

cd no-OS

# build the basic example on the ZedBoard (requires a .xsa hardware file)
python tools/scripts/no_os_build.py build \
   --project hello_world --variant basic --board zed \
   --hardware /path/to/system_top.xsa

# build and flash (requires a connected debug probe)
python tools/scripts/no_os_build.py build \
   --project hello_world --variant basic --board zed \
   --hardware /path/to/system_top.xsa \
   --probe openocd --flash

Where to get an XSA

Option 1 — Reuse an existing XSA (easiest).

If you already have an XSA from any other no-OS or Vivado project that targets your board, pass it directly with --hardware:

python tools/scripts/no_os_build.py build \
   --project hello_world --variant basic --board zed \
   --hardware /path/to/existing/system_top.xsa

Option 2 — Build an XSA from the ADI HDL repository.

The ADI HDL repository contains reference designs for many boards. Follow the ADI HDL build guide to generate a system_top.xsa for your board.

Expected Output

After programming the board and opening a serial terminal at 115200 baud, you should see:

*** no-OS Hello World ***

Hello World #1
Hello World #2
Hello World #3
...

A new line is printed every second. If nothing appears, check that you are connected to the correct serial device and that the baud rate is exactly 115200.