Zephyr RTOS Support for AMD Microblaze V: Complete FPGA & RISC-V Guide
Zephyr RTOS now officially supports AMD MicroBlaze V, bringing a Linux Foundation backed RISC-V real-time operating system to FPGA-based designs. AMD is transitioning away from FreeRTOS for MicroBlaze V and adopting Zephyr as its long-term scalable RTOS platform.
Key architectural characteristics:
- IPv6
- IPv4
- UDP
- TCP
- ICMPv4
- ICMPv6
Devicetree-based architecture: Makes supporting new boards quick and straightforward
Rich built-in networking support including:
What Is Zephyr RTOS?
Zephyr RTOS is an open-source real-time operating system hosted by the Linux Foundation. It is positioned as a modern RTOS implementation that has gained significant industry momentum.
Zephyr provides:
- A modern open-source RTOS implementation
- Strong community support and extensive documentation
- Significant industry adoption and growth
How Zephyr’s Devicetree Architecture Works on AMD FPGAs
Zephyr is designed with modularity and configurability at its core.
Kconfig allows developers to:
- Turn features on or off
- Configure networking
- Configure debugging
- Select scheduler algorithms
- Enable other Zephyr kernel capabilities
Configuration is typically defined in:
- Kconfig
- prj.conf
Robust and Secure Kernel Design
Zephyr includes:
- Support for multiple scheduling algorithms
- Native memory protection
- Fault handling mechanisms
This makes Zephyr suitable for embedded systems requiring both flexibility and robustness.
Zephyr RTOS History
Zephyr has evolved through multiple stages:
1991 – Launched as Virtuoso RTOS
2001 – Acquired by Wind River Systems
2015 – Renamed to Rocket and open sourced
2016 – Becomes Zephyr under the Linux Foundation
The transition to the Linux Foundation marked its formal establishment as a large-scale open-source RTOS project.
How to Build & Configure Zephyr Projects Using West, Kconfig and Devicetree
Zephyr projects follow a structured workflow consisting of cloning, configuration, and target setup.
West: Zephyr’s Meta Tool
Zephyr uses West for repository management.
Zephyr offers:
- A rich ecosystem of devices and features
- Strong community support backed by the Linux Foundation
- Devicetree architecture
- Hardware Abstraction Layer (HAL)
- Built-in POSIX compliance
- Additional features beyond those listed
How Kconfig Control Zephyr RTOS Features and Kernel Settings
FreeRTOS
- No enforced driver model
- Vendor SDKs provide drivers
Zephyr:
- Consistent driver/device model
- Improved portability across boards
How Devicetree Defines Hardware for Zephyr on AMD FPGAs
Devicetree:
- Describes target board or device hardware
- Uses <board>.dts files
Choose FreeRTOS:
- Tiny MCU app
- Minimal overhead
- Vendor SDK environment
- Simple scheduler needs
Choose Zephyr:
- Connected device (BLE/Wi-Fi/IP)
- Multiple boards/products
- Long-lived codebase
- Upstream driver support
- Standardized configuration
How AMD Integrates MicroBlaze V Hardware into Zephyr Using Lopper
AMD has extended West with its own command: lopper-command
Preprocessing flow: XSA File → SDTGen → west lopper-command → Zephyr
The XSA file goes through SDTGen, then through the west lopper-command, and then integrates with Zephyr. This preprocessing step enables hardware description integration into the Zephyr build process.
Why AMD Is Replacing FreeRTOS with Zephyr on MicroBlaze V
AMD is moving away from FreeRTOS and transitioning to Zephyr RTOS.
Zephyr can be thought of as a “Linux-like” RTOS.
Includes
- Extensive testing
- Regression testing and validation
After initial PROD release:
- Additional features are added
- Kernel updates are performed
Zephyr RTOS vs FreeRTOS for AMD FPGA Designs: Key Differences
FreeRTOS: A small, widely used real-time kernel (task scheduling + basic RTOS primitives). Think “RTOS core you add to your project.”
Zephyr: A full open-source RTOS project (kernel plus drivers, device model, networking stacks, filesystems, BLE, build system, testing tools, etc.). Think “RTOS + integrated platform.”
Footprint and Complexity
FreeRTOS: Tpically smaller and simpler to drop into bare-metal MCU projects.
Zephyr: Can be small, but it’s usually heavier because it’s an OS platform with integrated subsystems.
Build System and Configuration
The ISA describes:
- Registersa
- Instruction set
- Programmer’s model
The ISA consists of:
- Base instruction sets (rv32i, rv64i)
- Extensions (m, a, f, c, etc.)
Hardware Support and Drivers
Supported instruction sets and extensions:
- rv32i
- rv64i
- m (integer multiply/divide)
- a (atomic instructions)
- f (single-precision floating point, rv32i only, requires m)
- fd (double-precision floating point, rv64i only, requires m)
- c (compressed instructions)
- b, Zb[abcs] (bit manipulation extensions)
- Zicsr (CSR extension)
- Zifencei (instruction-fetch fence)
- Zicbom (cache block management)
Networking and Connectivity
Released in 2025.1
- Timer
- Uartlite
- Interrupt controller
Released in 2025.2
- GPIO
- SPI
- I2C
- 16550 UART
Additional Notes
- AXI stream works well; no driver required
- Ethernet support coming soon
- Zephyr CONFIG_XIP allows code/data split
- Many applications fit easily in BRAM
Licensing
- FreeRTOS: MIT license
- Zephyr: Apache 2.0 (includes explicit patent grant)
Both are commercially friendly.
Zephyr RTOS vs FreeRTOS for Your FPGA Design
How customizable is the AMD MicroBlaze V processor? Is it possible to add multiple hardware cores or threads to a single instantiation of the IP? If multi-core configurations are supported, how does Zephyr RTOS detect this hardware configuration?
The AMD MicroBlaze V processor is highly configurable, consistent with its RISC-V-based architecture and soft-processor implementation within AMD FPGAs. Designers can select supported ISA extensions (e.g., M, A, F, D, C, bit manipulation extensions, CSR, etc.) and determine whether certain operations are implemented in hardware (for performance) or emulated in software (to reduce resource utilization).
Because MicroBlaze V is implemented as a soft processor in programmable logic, system architects can instantiate multiple independent processor cores within the FPGA fabric if required by the application.
Zephyr RTOS uses Devicetree to describe hardware configuration. During the build process, Zephyr reads the hardware description (generated via XSA → SDTGen → west lopper-command) and integrates it into the system’s Devicetree configuration. If a multi-core configuration is instantiated and properly described in the hardware design, Zephyr detects the hardware layout through this Devicetree-based configuration mechanism.
Is it necessary to use one of the preset MicroBlaze V configurations?
No. While AMD provides preset configurations to accelerate development and improve design productivity, MicroBlaze V is highly configurable and can be tailored to meet specific application requirements.
Preset configurations are provided for convenience and faster time-to-design, but custom configurations are fully supported.
What devices is Zephyr RTOS compatible with?
Zephyr RTOS is supported on devices that are supported by AMD Vivado ML Design Suite and can accommodate a MicroBlaze V processor instance.
Because MicroBlaze V is implemented in programmable logic, Zephyr can run on any AMD FPGA device (including AMD FPGAs, Zynq families, and Versal adaptive SoCs) that:
· Is supported by Vivado
· Has sufficient programmable logic and memory resources to instantiate the MicroBlaze™ V processor and required peripherals
Are most Zephyr drivers still in Early Access?
No. The majority of drivers required for MicroBlaze V support have reached production quality status.
Production-quality drivers include:
· Timer
· Uartlite
· Interrupt controller
· GPIO
· SPI
· I2C
· 16550 UART
A small number of features are still being finalized and refined toward full production quality. AXI Stream functionality works without requiring a dedicated driver, and Ethernet support is forthcoming.
What is the smallest MicroBlaze V configuration that supports Zephyr?
Any MicroBlaze V configuration can support Zephyr RTOS, provided that a timer peripheral is available.
A timer is required to support the RTOS scheduling and timekeeping functionality. As long as the processor configuration includes a timer and sufficient system resources, Zephyr can be deployed.
What version of Vivado is required to use MicroBlaze V with Zephyr?
It is recommended to use the latest version of Vivado ML Design Suite.
For best compatibility, the Vivado version should align with the Zephyr version being used in the project. Matching toolchain and RTOS versions ensures consistent hardware description generation and integration.
Is Zephyr included in the Vivado installation?
No. Zephyr RTOS is not included in the Vivado installation.
Zephyr is an open-source RTOS hosted by the Linux Foundation and must be installed separately. Integration with Vivado-based hardware designs is performed using the Zephyr build system, West meta-tool, and the AMD-specific lopper-command flow.
What are the limitations of FreeRTOS that are motivating the transition to Zephyr?
The transition from FreeRTOS to Zephyr is driven by several strategic and technical considerations:
· Strong and growing community momentum behind Zephyr
· Backing by the Linux Foundation
· Rich ecosystem of devices and features
· Devicetree-based hardware abstraction
· Built-in POSIX compliance
· Improved portability across architectures
· Reduced long-term maintenance burden
Zephyr’s broader ecosystem support and long-term sustainability make it a more scalable and future-ready platform for AMD processor roadmaps.
Zephyr RTOS Support Levels at AMD: EA (Early Access) vs PROD (Production)
Zephyr support at AMD is categorized into EA (Early Access) and PROD (Production).
EA (Early Access)
PROD (Production)
AMD Zephyr RTOS Roadmap for MicroBlaze V and Cortex Processors
Roadmaps subject to change
Important Notes:
- FreeRTOS not available on MicroBlaze V
- FreeRTOS maintenance continues for all Arm processors
Understanding RISC-V ISA Support in AMD MicroBlaze V
RISC-V International manages the RISC-V Instruction Set Architecture (ISA).
- AMD is a strategic member
- 4500 members across 70 countries
ISA Overview
The ISA specification is open source, but implementations are not required to be open source.
How MicroBlaze V Enables RISC-V Processing on AMD FPGAs
AMD MicroBlaze V Overview:
- Fast soft-processor performance
- Highest flexibility
RISC-V ISA Extensions Supported by AMD MicroBlaze V
Configurable ISA Implementation
Designers can:
- Implement operations in hardware (speed)
- Emulate in software (resource savings)
Customer feedback is requested regarding:
- Floating point usage
- Double precision on 32-bit
RISC-V Compressed Instructions (C Extension)
Current Zephyr AXI Driver Support for AMD MicroBlaze V
Current Status: 32-bit CPU support available now
Zephyr AXI Peripheral Drivers
The Future of Zephyr RTOS on MicroBlaze V and FPGA Platforms
As AMD transitions from FreeRTOS to Zephyr, especially for MicroBlaze V developers gain a powerful, future-ready, Linux Foundation–backed RTOS designed for connected, scalable embedded systems. Whether you're developing on AMD FPGAs, evaluating MicroBlaze V for a new design, or planning a long-term embedded product roadmap, Zephyr provides the flexibility and ecosystem support to scale with you.
If you're developing a Zephyr-based MicroBlaze V design and need AMD FPGAs, AXI peripherals, or RISC-V–compatible components, we can help secure production-ready inventory. Microchip USA specializes in supplying hard-to-find, allocated, obsolete, and production-volume electronic components. Our team helps you secure the AMD devices and supporting parts you need. Contact us today to discuss your project requirements.