Embedded Systems Altera NIOS II Software Development: Part I Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-1 Overview • NIOS II programs and associated projects – Applications – User libraries – Board support packages (BSPs) • Programming a NIOS II system – User programs – C standard library – Hardware abstraction layer (HAL) and HAL layers – Device drivers • HAL Architecture and Services • Developing Programs Using the HAL Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-2 1 NIOS II Programs • Each NIOS II program consists of: – an application project, – optional user library projects, and – a board support package (BSP) project • The build process creates an Executable and Linking Format File (.elf) which runs on a NIOS II processor. Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-3 NIOS II Software Project Types: Application Project • A NIOS II C/C++ application project consists of a collection of source code, plus a makefile • A typical characteristic of an application is that one of the source files contains function main() • An application includes code that calls functions in libraries and BSPs • The makefile contains commands to: – compile the source code – link it with a BSP and one or more optional libraries – create one .elf file Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-4 2 NIOS II Software Project Types: User Library Project • A user library project is a collection of source code compiled to create a single library archive file (.a) – Libraries often contain reusable, general purpose functions that multiple application projects can share – A collection of common arithmetical functions is one example • A user library does not contain a main() function Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-5 NIOS II Software Project Types: BSP Project • A NIOS II BSP project is a specialized library containing system-specific support code • A BSP provides a software runtime environment customized for one processor in an SOPC Builder system • The NIOS II EDS provides tools to modify settings that control the behavior of the BSP • A BSP contains the following elements: – Hardware abstraction layer – Newlib C standard library – Device drivers – Optional software packages – Optional real-time operating system Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-6 3 Overview of the Hardware Abstraction Layer • The HAL provides a simple device driver interface for programs to connect to the underlying hardware • The HAL application program interface (API) is integrated with the ANSI C standard library • The HAL API allows access to devices and files using familiar C library functions – printf(), fopen(), fwrite(), etc. • The HAL serves as a device driver package for NIOS II processor systems – provides a consistent programming interface to the peripherals in a NIOS II system Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-7 HAL Architecture and Services • Integration with the newlib ANSI C standard library – Provides the familiar C standard library functions • Device drivers – Provides access to each device in the system • The HAL API – Provides a consistent, standard interface to HAL services, such as device access, interrupt handling, and alarm facilities • System initialization – Performs initialization tasks for the processor and the runtime environment before main() • Device initialization – Initializes each device in the system before main() runs Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-8 4 Layers of a HAL-Based System Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-9 HAL Generic Device Models • The HAL provides generic device models for classes of peripherals found in embedded systems – timers, Ethernet MAC/PHY chips, and I/O peripherals that transmit character data, etc. • Generic device models allow programs to use a consistent API, regardless of the underlying hardware Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-10 5 HAL Device Model Classes • Character-mode devices – Hardware peripherals that send and/or receive characters serially, such as a UART. • Timer devices – Hardware peripherals that count clock ticks and can generate periodic interrupt requests. • File subsystems – A mechanism for accessing files stored in physical device(s) • Ethernet devices – Devices that provide access to an Ethernet connection for a networking stack • Direct memory access (DMA) devices – Peripherals that perform bulk data transactions from a data source to a destination • Flash memory devices – Nonvolatile memory devices that use a special programming protocol to store data Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-11 HAL Peripherals • All peripherals must have a header file that defines the peripheral’s low-level interface to hardware • Therefore, all peripherals support the HAL to some extent • However, some peripherals might not provide device drivers • If drivers are not available, use only the definitions provided in the header files to access the hardware • Some peripherals provide functions that are not based on the HAL generic device models – For example, Altera provides a general-purpose parallel I/O (PIO) core for use with the NIOS II processor system – The PIO peripheral does not fit in any class of generic device models provided by the HAL, and so it provides a header file and a few dedicated functions only – User pushbuttons and LEDs are examples of these Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-12 6 Developing Programs Using The HAL • NIOS II Development Flows – The NIOS II Embedded Design Suite (EDS) provides two distinct development flows for creating NIOS II programs • NIOS II Software Build Tools (SBT for Eclipse or command line) • NIOS II Integrated Development Environment (IDE) • HAL BSP Settings – Every NIOS II board support package (BSP) has settings that determine the BSP’s characteristics – For example, HAL BSPs have settings to identify the hardware components associated with standard devices such as stdout • Defining and manipulating BSP settings is an important part of NIOS II project creation • BSP settings can be modified with the NIOS II BSP Editor, with command-line options, or with Tcl scripts Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-13 The NIOS II HAL Project Structure Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-14 7 The NIOS II HAL Project Structure • Every HAL-based NIOS II program consists of two NIOS II projects – Your application-specific code is contained in one project (the user application project), and – it depends on a separate BSP project (the HAL BSP). • The application project contains all the code you develop • The executable image for your program ultimately results from building both projects • With the NIOS II Software Build Tools for Eclipse, the tools create the HAL BSP project when you create your application project • The BSP project depends on the SOPC Builder system, defined by a SOPC Information File (.sopcinfo) – The SOPC file is created using the SPOC Builder tool within the Altera Quartus software Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-15 The system.h System Description File • The system.h file provides a complete software description of the NIOS II system hardware • The system.h file describes each peripheral in the system and provides: – The hardware configuration of the peripheral – The base address – Interrupt request (IRQ) information (if any) – A symbolic name for the peripheral Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-16 8 Excerpts from a system.h File Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-17 Data Widths and the HAL Type Definitions • For embedded processors such as the NIOS II processor, it is often important to know the exact width and precision of data • Because the ANSI C data types do not explicitly define data width, the HAL uses a set of standard type definitions instead • The ANSI C types are supported, but their data widths are dependent on the compiler’s convention • The header file alt_types.h defines the HAL type definitions Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-18 9 The HAL and GNU Toolchain Type Definitions and Data Widths Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-19 UNIX-Style Interface • The HAL API provides a number of UNIX-style functions – The UNIX-style functions provide a familiar development environment for new NIOS II programmers – Can ease the task of porting existing code to run in the HAL environment • The HAL uses these functions primarily to provide the system interface for the ANSI C standard library – For example, the functions perform device access required by the C library functions defined in stdio.h. Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson Lecture 5-20 10 Available UNIX-style Functions • _exit() • open() • close() • read() • fstat() • sbrk() • getpid() • settimeofday() • gettimeofday() • stat() • ioctl() • usleep() • isatty() • wait() • kill() • write() • lseek() Electrical & Computer Engineering – Embedded Systems Dr. Jeff Jackson