COBHAM NOEL-ARTYA7-EX User manual

.
NOEL-ARTYA7-EX
Quick Start Guide
2020 User's Manual
The most important thing we build is trust
NOEL-ARTYA7-EX Quick Start Guide
NOEL-ARTYA7-EX-QSG 1 www.cobhamaes.com/gaisler
December 2020, Version 1.2

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 2www.cobhamaes.com/gaisler
Table of Contents
1. Introduction .......................................................................................................................... 4
1.1. Overview ................................................................................................................... 4
1.2. Availability ................................................................................................................ 4
1.3. Prerequisites ............................................................................................................... 4
1.4. References .................................................................................................................. 4
2. Overview .............................................................................................................................. 5
2.1. Boards ....................................................................................................................... 5
2.2. Design summary ......................................................................................................... 5
2.3. Processor features ........................................................................................................ 5
2.4. Software Development Environment ............................................................................... 5
2.4.1. RTEMS ........................................................................................................... 5
2.4.2. Bare C cross-compiler ....................................................................................... 6
2.4.3. Linux .............................................................................................................. 6
2.4.4. VxWorks 7 ...................................................................................................... 6
2.4.5. GRMON ......................................................................................................... 6
3. Board Configuration ............................................................................................................... 7
3.1. Push buttons ............................................................................................................... 7
3.2. Switches .................................................................................................................... 7
3.3. LEDs ......................................................................................................................... 7
3.4. Connectors ................................................................................................................. 7
3.5. Memories ................................................................................................................... 7
3.6. Programming the bitstream ........................................................................................... 7
4. GRMON hardware debugger .................................................................................................... 8
4.1. Overview ................................................................................................................... 8
4.2. NOEL-V support ......................................................................................................... 8
4.3. NOEL-V limitations ..................................................................................................... 8
4.4. Debug-link alternatives ................................................................................................. 9
4.4.1. Connecting via the Digilent USB/JTAG interface .................................................... 9
4.4.2. Connecting via the Ethernet debug interfaces ......................................................... 9
4.4.3. Connecting via the serial UART .......................................................................... 9
4.5. First steps .................................................................................................................. 9
4.6. Connecting to the board ............................................................................................... 9
4.7. Get system information ............................................................................................... 10
4.8. Load a RAM application ............................................................................................. 10
4.9. Debugging with GDB ................................................................................................. 11
5. RTEMS Real Time Operating System ...................................................................................... 13
5.1. Overview .................................................................................................................. 13
5.2. Features ................................................................................................................... 13
5.3. Install toolchain and kernel .......................................................................................... 13
5.4. Building an RTEMS sample application ......................................................................... 13
5.5. Running and debugging with GRMON .......................................................................... 13
5.6. RISC-V and NOEL-V integration with RTEMS .............................................................. 15
5.6.1. CSRs ............................................................................................................. 15
5.6.2. Clock tick ...................................................................................................... 15
5.6.3. Exceptions ..................................................................................................... 15
5.6.4. NOEL-V BSP variants ..................................................................................... 15
5.6.5. Console driver ................................................................................................ 16
5.6.6. Memory layout ............................................................................................... 16
5.6.7. Work area ...................................................................................................... 16
5.6.8. Symmetric Multiprocessing ............................................................................... 16
5.7. Device tree ............................................................................................................... 16
5.7.1. Background .................................................................................................... 16
5.7.2. GRMON ........................................................................................................ 16
5.8. Compiler options ....................................................................................................... 17
5.9. Building the kernel .................................................................................................... 17

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 3www.cobhamaes.com/gaisler
5.9.1. RTEMS test suite ............................................................................................ 17
5.10. Building the tool chain .............................................................................................. 18
6. Bare-metal cross-compiler ...................................................................................................... 19
6.1. Overview .................................................................................................................. 19
6.2. Installation ................................................................................................................ 19
6.3. Compiling with NCC ................................................................................................. 19
6.4. Compiler options ....................................................................................................... 19
6.5. Multilibs .................................................................................................................. 19
6.6. Running and debugging with GRMON .......................................................................... 20
7. Linux ................................................................................................................................. 21
7.1. Overview .................................................................................................................. 21
7.2. Step by step instructions ............................................................................................. 21
8. RTEMS Example applications ................................................................................................ 25
8.1. Basic examples .......................................................................................................... 25
8.1.1. hello .......................................................................................................... 25
8.1.2. tasks .......................................................................................................... 25
8.1.3. dhrystone .................................................................................................. 25
8.1.4. coremark .................................................................................................... 25
8.1.5. Creating a custom application ............................................................................ 26
8.2. Driver manager examples ............................................................................................ 26
8.2.1. Introduction .................................................................................................... 26
8.2.2. Requirements .................................................................................................. 26
8.2.3. Build ............................................................................................................. 26
8.2.4. Targets .......................................................................................................... 26
8.2.5. Comments ...................................................................................................... 27
8.2.6. Limitations ..................................................................................................... 27
9. Support ............................................................................................................................... 28

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 4www.cobhamaes.com/gaisler
1. Introduction
1.1. Overview
This document is a quick start guide for the NOEL-ARTYA7-EX design. The guide is mainly how-to oriented
and does not go into many technical details. For more in-depth information we refer to respective products User's
Manual. See the reference list below.
1.2. Availability
The FPGA bitstreams and software environment is available on the NOEL-ARTYA7-EX web page: https://
www.gaisler.com/NOEL-ARTYA7.
1.3. Prerequisites
To use the provided bitstream, the user needs:
• Digilent Arty A7 FPGA Development Board (A7-100T version)
• GRMON 3.2.9 evaluation version available at https://www.gaisler.com/grmon.
• Xilinx Vivado Design Suite to program the FPGA ([RD-7]).
1.4. References
Table 1.1. References
RD-1 NOEL-ARTYA7-EX User's Manual [https://www.gaisler.com/NOEL-ARTYA7]
RD-2 GRMON User's Manual [https://www.gaisler.com/doc/grmon3.pdf]
RD-3 RTEMS homepage [https://www.rtems.org]
RD-4 RTEMS User Manual [https://docs.rtems.org/branches/master/user/index.html]
RD-5 Arty A7 Reference Manual [https://reference.digilentinc.com/reference/programmable-log-
ic/arty-a7/reference-manual]
RD-6 Buildroot homepage [https://www.buildroot.com]
RD-7 Xilinx Vivado Design Suite [https://www.microsemi.com/product-directory/program-
ming/4977-flashpro]

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 5www.cobhamaes.com/gaisler
2. Overview
2.1. Boards
The NOEL-ARTYA7-EX design can be used with the Digilent Arty A7 FPGA Development Board (A7-100T
version) ([RD-5]).
2.2. Design summary
The NOEL-ARTYA7-EX is a GRLIB design which includes the following features:
• Cobham Gaisler NOEL RISC-V RV64G dual-core processor
• RISC-V Debug module
• L2 cache with 256 KiB in 4 ways
• Memory controller and 256 MiB SDRAM.
• Ethernet 10/100/1000 Mbit MAC interface
• APBUART serial interface
• GRLIB AMBA AHB bus controller
• JTAG, Ethernet EDCL and UART debug link
• AHB bus trace
• 20-pin GPIO controller
For more details on the NOEL-ARTYA7-EX design, see the NOEL-ARTYA7-EX User's Manual ([RD-1]). For
details about the the interfaces' connections in the board, see Chapter 3.
2.3. Processor features
• 64-bit architecture
• Hardware multiply and divide units
• Atomic instruction extension
• 32/64bitfloatingpointextensionsusingnon-pipelinedareaefficientFPUorhigh-performancefullypipelined
IEEE-754 FPU
• Machine, supervisor and user mode. RISC-V standard MMU with configurable TLB.
• User level interrupts
• RISC-V standard PLIC (platform interrupt controller)
• RISC-V standard PMP (physical memory protection)
• RISC-V standard external debug support
• Advanced 7-stage dual-issue in-order pipeline
• Dynamic branch prediction, branch target buffer and return address stack
• Four full ALUs, two of them late in the pipeline to reduce stalls
• Separate instruction and data L1 cache (Harvard architecture) with snooping
2.4. Software Development Environment
2.4.1. RTEMS
RTEMS is a hard Real Time Operating System.
The NOEL-V software development environment includes an RTEMS kernel, BSP tool chain and examples. This
allows for development of real-time multitasking applications with POSIX support. The RTEMS tool chain is
currently provided for the Linux 64-bit host operating systems.
Chapter 5 describes how to use RTEMS with NOEL-ARTYA7-EX.
The recommended method to load software onto NOEL-ARTYA7-EX is by connecting to a debug interface of
the board through the GRMON hardware debugger (Chapter 4).

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 6www.cobhamaes.com/gaisler
2.4.2. Bare C cross-compiler
NCC is a cross-compilation system for NOEL-V processors. It is based on the GNU compiler tools, the newlib
C library and a support library for programming NOEL-V systems. The cross-compiler allows compilation of C
and C++ single-threaded applications.
Chapter 6 describes how to use NCC with NOEL-ARTYA7-EX.
2.4.3. Linux
Buildroot can be used to easily create a bootable Linux image for NOEL-V [RD-6]. It automatically creates a
toolchain and supports a large number of useful userspace applications which can be included in the generated
root file system. Included in the software development environment is a NOEL-ARTYA7-EX BSP for Buildroot
which provides the necessary driver support.
See Chapter 7 for instructions on how to create a Linux image for NOEL-ARTYA7-EX with Buildroot.
2.4.4. VxWorks 7
Please contact [email protected] for information about NOEL-V BSPs for VxWorks 7.
2.4.5. GRMON
GRMON is a hardware monitor which allows non-intrusive debugging and execution control of software on
NOEL-ARTYA7-EX. GRMON provides a RISC-V GDB server. GRMON is available for Linux and Windows
host operating systems.
NOEL-V can be used with GRMON GUI.
Chapter 4 describes how to use GRMON with NOEL-ARTYA7-EX.

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 7www.cobhamaes.com/gaisler
3. Board Configuration
This chapter describes boards items as used by the NOEL-ARTYA7-EX design.
Please see Arty A7 Reference Manual for a detailed legend of the reference designators.
3.1. Push buttons
•BTN[0]: Main reset to the FPGA design
•BTN[1..]: GPIO inputs [5..7]
3.2. Switches
•SW[0..2] DIP switch: GPIO inputs [0..2]
•SW[3] acts as select signal for the UART interface. When "ON" if selects the UART debug link. When
"OFF" it selects the console UART
3.3. LEDs
•LED[0..3]: Connected to GPIO0 outputs [16..19]
3.4. Connectors
•J10: USB JTAG interface via Digilent module with micro-B USB connector. See (Chapter 4).
• Ethernet PHY SGMII interface with RJ-45 connector. See (Chapter 4).
3.5. Memories
The NOEL-ARTYA7-EX has 256 MiB of SDRAM available on the on-chip bus.
3.6. Programming the bitstream
A Xilinx Vivado script to program the FPGA is provided with the bitfile distribution. The bitstream folder contains
several bistreams which represent different configurations of the processor (EX1,EX2, ecc.). Select one of the
bitstreams (described in [RD-1]. and follow the instructions below to program the FPGA:
To program the FPGA please follow these instructions:
1. Connect the PC and the board using a standard micro-USB cable into the connector USB-JTAG J10.
2. Make sure that Vivado is added to your path variables
3. Open a terminal in the downloaded folder and issue the following command to launch Vivado:
vivado -mode tcl -notrace -source doprog.tcl
4. To program the FPGA with the selected configuration, run in the Vivado console (in this case for EX1):
doprog EX1
5. Once the FPGA has been programmed, it is possible to connect to the board using GRMON, using the
command:
grmon -digilent
Please see (Chapter 4) for further information regarding GRMON and the available debug links.
Alternatively, the bitfile (.bit) can be programmed to the Digilent ARTY-A7 using the Vivado design suite
graphical interface. Start Vivado and select the menu item Flow -> Open Hardware Manager. Once the FPGA
has been programmed, remember to close the hardware manager before connecting with GRMON.

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 8www.cobhamaes.com/gaisler
4. GRMON hardware debugger
4.1. Overview
GRMON is a debug monitor used to develop and debug GRLIB systems with NOEL and LEON processors. The
target system, including the processor and peripherals, is accessed on the AHB bus through a debug-link connected
to the host computer. GRMON has GDB support which makes C/C++ level debugging possible by connecting
GDB to the GRMON's GDB socket.
With GRMON one can for example:
• Inspect NOEL-V and peripheral registers
• Upload applications to RAM with the load command.
• Program the FLASH with the flash command.
• Control execution flow by starting applications (run), continue execution (cont), single-stepping (step), in-
serting breakpoints/watchpoints (bp) etc.
• Inspect the current CPU state listing the back-trace, instruction trace and disassemble machine code.
The first step is to set up a debug link in order to connect to the board. The following section outlines which
debug interfaces are available and how to use them on the NOEL-ARTYA7-EX design. After that, a basic first
inspection of the board is exemplified.
GRMON is described on the homepage [https://www.gaisler.com/index.php/products/debug-tools] and in detail
in the GRMON User Manual [RD-2].
4.2. NOEL-V support
Most of the GRMON commands available for LEON are also available for NOEL-V. GRMON commands avail-
able for NOEL-V include:
•load: RISC-V ELF file support. Symbols are loaded from the ELF file and can be used instead of addresses
for most commands.
•run, cont, go, step: execution control
•mem, wmem: read/write any on-chip address.
•disassemble: RISC-V instruction disassembly
•inst: CPU instruction trace
•bp: Hardware and software breakpoint
•bt: call tree backtrace, based on dwarf debug information
•reg: read and write all RISC-V CPU general purpose registers and CSR registers. CSR registers can be
specified by name or address.
•mmu: inspect and walk MMU tables
•forward: UART forwarding to the GRMON console
•info reg, info sys: Supports the NOEL-V related GRLIB devices.
•gdb: Creates a GDB server for connecting with a GDB compiled with RISC-V as target.
4.3. NOEL-V limitations
• GRMON can report only the following reasons for termination of execution:
• An ebreak instruction was executed.
• The signal haltreq was asserted by the debug module. Typically as a consequence of the user hitting
ctrl+c in the GRMON terminal.
In the current NOEL-V release, execution can not be aborted at an arbitrary exception or hardware breakpoint.
• CPU local AHB trace is not available. The NOEL-ARTYA7-EX design includes an AHBTRACE which can
be controlled with the GRMON command at.
The limitations listed above are present in the current release of NOEL-V. The features mentioned are part of the
schedule for future releases.

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 9www.cobhamaes.com/gaisler
4.4. Debug-link alternatives
4.4.1. Connecting via the Digilent USB/JTAG interface
Please see GRMON User's Manual for information on how to set up the required Digilent Adept driver software.
Then connect the PC and the board using a standard USB cable into the USB-mini J10 USB-JTAG connector and
issue the following command:
grmon -digilent
4.4.2. Connecting via the Ethernet debug interfaces
If another address is wanted for the Ethernet debug link then one of the other debug links must be used to connect
GRMON to the board. The EDCL IP address can then be changed using GRMON's edcl command. This new
address will persist until next system reset.
With the Ethernet Debug Communication Link 0 address set to 192.168.0.51 the GRMON command to connect
to the board is:
grmon -eth 192.168.0.51
4.4.3. Connecting via the serial UART
Make sure the switch SW[3] is selecting the UART debug link. Please see GRMON User's Manual for instructions
how to connect GRMON to a board using a serial UART connection. The PC is connected using a standard USB
cable to serial converter) to the USB-mini J10 connector and then starting GRMON without debug-link option
(default is UART) or by specifying which PC UART using the -uart COMPORT_NAME command line switch.
For example:
grmon -uart /dev/ttyUSB0
4.5. First steps
The previous sections have described which debug-links are available and how to start using them with GRMON.
The subsections below assume that GRMON, the host computer and the NOEL-ARTYA7-EX board have been
set up so that GRMON can connect to the board.
When connecting to the board for the first time it is recommended to get to know the system by inspecting the
current configuration and hardware present using GRMON. With the info sys command more details about the
system is printed and with info reg the register contents of the I/O registers can be inspected. Below is a list of
items of particular interest:
• AMBA system frequency is printed out at connect, if the frequency is wrong then it might be due to noise in
auto detection (small error). See -freq flag in the GRMON User's Manual [RD-2].
• Memory location and size configuration is found from the info sys output.
• If the Ethernet debug link is present, one can view and change the EDCL IP using the edcl command as
described in the GRMON User's Manual [RD-2].
4.6. Connecting to the board
In the following example a JTAG debug link is used to connect to the board. The auto-detected frequency, memory
parameters and stack pointer are verified by looking at the GRMON terminal output below.
grmon -digilent
GRMON version: v3.2.8.3-101-gf451057 internal version
OS: Linux
Command line: grmon -digilent -jtagcable 2
GRMON debug monitor v3.2.8.3-101-gf451057 64-bit internal version
Copyright (C) 2020 Cobham Gaisler - All rights reserved.
For latest updates, go to http://www.gaisler.com/
Comments or bug-reports to [email protected]
This internal version will expire on 27/11/2021

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 10 www.cobhamaes.com/gaisler
JTAG chain (1): xc7a200t
Device ID: 0x291
GRLIB build version: 4258
Detected frequency: 40.0 MHz
Component Vendor
NOEL-V RISC-V Processor Cobham Gaisler
NOEL-V RISC-V Processor Cobham Gaisler
AHB-to-AHB Bridge Cobham Gaisler
AHB Debug UART Cobham Gaisler
JTAG Debug Link Cobham Gaisler
EDCL master interface Cobham Gaisler
L2-Cache Controller Cobham Gaisler
Generic AHB ROM Cobham Gaisler
Xilinx MIG Controller Cobham Gaisler
AHB/APB Bridge Cobham Gaisler
RISC-V CLINT Cobham Gaisler
RISC-V PLIC Cobham Gaisler
RISC-V Debug Module Cobham Gaisler
AHB/APB Bridge Cobham Gaisler
AHB-to-AHB Bridge Cobham Gaisler
AMBA Trace Buffer Cobham Gaisler
Version and Revision Register Cobham Gaisler
AHB Status Register Cobham Gaisler
General Purpose I/O port Cobham Gaisler
GR Ethernet MAC Cobham Gaisler
Gaisler RGMII Interface Cobham Gaisler
On chip Logic Analyzer Cobham Gaisler
Modular Timer Unit Cobham Gaisler
Generic UART Cobham Gaisler
Use command 'info sys' to print a detailed report of attached cores
grmon3>
4.7. Get system information
One can limit the output to certain cores by specifying the core(s) name(s) to the info sys and info reg commands.
As seen below the memory parameters, first UART and first Timer core information is listed.
grmon3> info sys mig0
mig0 Cobham Gaisler Xilinx MIG DDR3 Controller
AHB: 40000000 - 80000000
SDRAM: 1024 Mbyte
grmon3> info sys uart0 gptimer0
uart0 Cobham Gaisler Generic UART
APB: 80000100 - 80000200
IRQ: 1
Baudrate 38422, FIFO debug mode available
gptimer0 Cobham Gaisler Modular Timer Unit
APB: 80000300 - 80000400
IRQ: 2
16-bit scalar, 2 * 32-bit timers, divisor 80
grmon3> info reg -v ahbstat0
AHB Status Register
0x80000f00 Status register 0x00000012
9 ce 0x0 Correctable error
8 ne 0x0 New error
7 hw 0x0 HWRITE on error
6:3 hm 0x2 HMASTER on error
2:0 hs 0x2 HSIZE on error
0x80000f04 Failing address register 0x80000f00
4.8. Load a RAM application
An application linked to RAM can be loaded directly with the load command and run with the run command. The
dtb command is used to load a device tree description for the board. In the example below, the file board.dtb
should be changed into the name of the target board .dtb file.
grmon3> load hello.elf
40000000 .text 142.0kB / 142.0kB [===============>] 100%
400237D0 .rtemsroset 96B [===============>] 100%
40024840 .data 4.4kB / 4.4kB [===============>] 100%
Total size: 146.44kB (777.96kbit/s)
Entry point 0x40000000
Image hello.elf loaded

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 11 www.cobhamaes.com/gaisler
grmon3> forward enable uart0
I/O forwarding to uart0 enabled
grmon3> dtb board.dtb
DTB will be loaded to the stack
grmon3> run
hello, world
CPU 0: Forced into debug mode
0x4001607c: 00100073 ebreak <_CPU_Fatal_halt+36>
CPU 1: Interrupted!
0x40011018: 10500073 wfi <_CPU_Thread_Idle_body+0>
The line hello, world is the program output which is forwarded to the GRMON terminal.
4.9. Debugging with GDB
It possible to connect the GDB debugger to GRMON to be able to debug programs at source level. Either start
GRMON with the -gdb flag or enter the gdb command in GRMON.
grmon3> gdb
Started GDB service on port 2222.
GDB is included with the RTEMS toolchain as riscv-rtems5-gdb:
user@workstation:~$ riscv-rtems5-gdb
GNU gdb (GDB) 8.3
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "--host=x86_64-pc-linux-gnu --target=riscv-rtems5".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb)
Specify the filename of the image to debug using the file command:
(gdb) file /home/user/riscv/demo/hello/hello.exe
Reading symbols from /home/user/riscv/demo/hello/hello.exe...
Connect to GRMON using target extended-remote:
(gdb) target extended-remote :2222
Remote debugging using :2222
0x0000000000000000 in ?? ()
The image can be loaded onto the target using the load command. This needs to be done before starting or
restarting the program.
(gdb) load
Loading section .start, size 0x4c lma 0x40000000
Loading section .text, size 0x132e8 lma 0x4000004c
Loading section .rodata, size 0x120a0 lma 0x40013338
Loading section .sdata2, size 0x30 lma 0x400253d8
Loading section .eh_frame, size 0x4 lma 0x40025408
Loading section .init_array, size 0x8 lma 0x40025410
Loading section .fini_array, size 0x8 lma 0x40025418
Loading section .rtemsroset, size 0x68 lma 0x40025420

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 12 www.cobhamaes.com/gaisler
Loading section .data, size 0x768 lma 0x40025488
Loading section .htif, size 0x1000 lma 0x40025c00
Loading section .sdata, size 0xa8 lma 0x40027000
Start address 0x40000000, load size 158864
Transfer rate: 62 KB/sec, 7943 bytes/write.
RTEMS images expect register a1 to contain a pointer to a device tree description. This can be set up with the
dtb command provided by GRMON. Use the mon prefix to execute a command in GRMON and load the device
tree using dtb:
(gdb) mon dtb noel-xilinx-artya7.dtb
DTB will be loaded to the stack
Use the break command to insert a breakpoint at the Init function:
(gdb) break Init
Breakpoint 1 at 0x40000170: file test.c, line 13.
The program can now be executed using the run command. GDB should break the execution once the program
reaches the Init function.
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/user/riscv/demo/hello/hello.exe
Breakpoint 1, Init (ignored=1073914168) at test.c:13
13 puts("");
At this stage one can, for example, step through the program with step or next, print the values of variables
with p, or continue execution with the cont command.
(gdb) cont
Continuing.
hello, world
The following message is printed if the RTEMS program exits normally.
*** FATAL ***
fatal source: 5 (RTEMS_FATAL_SOURCE_EXIT)
fatal code: 0 (0x00000000)
RTEMS version: 5.0.0.94bddc9c5daf258a8d0981e63bf4180b7b249677
RTEMS tools: 9.3.0 20200312 (RTEMS 5, RSB 5 (3bd11fd4898b), Newlib 7947581)
executing thread ID: 0x08a010001
executing thread name: UI1
Program received signal SIGTRAP, Trace/breakpoint trap.
_CPU_Fatal_halt (source=source@entry=5, error=error@entry=0)
at /home/user/riscv/leon-rtems/build/../c/src/lib/libbsp/riscv/riscv/
../../../../../../bsps/riscv/riscv/start/bsp_fatal_halt.c:43
43 asm ("ebreak");
(gdb)

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 13 www.cobhamaes.com/gaisler
5. RTEMS Real Time Operating System
5.1. Overview
RTEMS is a real time operating system that supports many processor families [RD-3]. Cobham Gaisler distributes
a precompiled RTEMS toolchain for NOEL-V. This section gives the reader a brief introduction on how to use
RTEMS together with the NOEL-ARTYA7-EX design. It will be demonstrated how to install the toolchain and
build an existing sample RTEMS project and run it on the board using GRMON.
The NOEL-V RTEMS distribution includes a prebuilt toolchain with GNU Binutils, GCC and Newlib. The sup-
ported host operating system is Linux. It also contains prebuilt RTEMS kernels for the NOEL-V, including 32-bit
and 64-bit versions. Support is included for the NOEL-ARTYA7-EX interrupt controller, timer and UART.
Sample RTEMS projects are available within the toolchain package, installed in the examples directory.
5.2. Features
• Kernel:
• BSP variants for rv32i, rv32im, rv32ima, rv32imafd, rv64im, rv64ima and rv64imafd.
• Uni-processor and SMP kernels available.
• RTEMS POSIX support
• Based on RTEMS master as of June 2020. (Exact rtems.git commit hash can be found in the README
file in the root directory of the toolchain distribution.)
• NOEL-V BSP
• Console driver for APBUART
• Interrupt controller (PLIC and CLINT)
• Clock driver via CLINT mtime
• GCC 9.3.0
5.3. Install toolchain and kernel
The toolchain and source can be downloaded from https://www.gaisler.com/NOEL-ARTYA7.
First extract the toolchain and kernel archive into /opt. In order for the compiler to be found, the binary directory
/opt/rtems-noel-1.0.4/bin has to be added to the PATH variable as below:
$ cd /opt
$ tar xf rtems-noel-1.0.4.tar.bz2
$ export PATH=$PATH:/opt/rtems-noel-1.0.4/bin
5.4. Building an RTEMS sample application
Once the toolchain is set up, you can compile and link a sample RTEMS application by doing:
$ cd /opt/rtems-noel-1.0.4/examples/hello
$ make
riscv-rtems5-gcc --pipe -march=rv64ima -mabi=lp64 \
-B/opt/rtems-noel-1.0.4/kernel/riscv-rtems5/noel64ima/lib \
-specs bsp_specs -qrtems -c test.c -o test.o
riscv-rtems5-gcc --pipe -march=rv64ima -mabi=lp64 \
-B/opt/rtems-noel-1.0.4/kernel/riscv-rtems5/noel64ima/lib \
-specs bsp_specs -qrtems -Wl,--gc-sections test.o -o hello.exe
The default load address is at the start of the RAM, i.e. 0x00000000.
See Chapter 8 for more information on the available examples.
5.5. Running and debugging with GRMON
Once your executable is compiled, connect to your NOEL-ARTYA7-EX with GRMON. The following log shows
how to load and run an executable. Note that the console output is redirected to GRMON by the use of the -u

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 14 www.cobhamaes.com/gaisler
command line switch, so that target application console output (APBUART) is shown directly in the GRMON
console.
Example 5.1.
$ grmon -digilent -u
GRMON debug monitor v3.2.9 64-bit version
grmon3> dtb board.dtb
DTB will be loaded to the stack
grmon3> load hello.exe
00000000 .start 76B [===============>] 100%
0000004C .text 98.6kB / 98.6kB [===============>] 100%
00018AB0 .rodata 83.5kB / 83.5kB [===============>] 100%
0002D8E0 .sdata2 48B [===============>] 100%
0002D910 .eh_frame 4B [===============>] 100%
0002D918 .init_array 8B [===============>] 100%
0002D920 .fini_array 8B [===============>] 100%
0002D928 .rtemsroset 112B [===============>] 100%
0002D998 .data 2.3kB / 2.3kB [===============>] 100%
0002E2C0 .htif 4.0kB / 4.0kB [===============>] 100%
00030000 .sdata 208B [===============>] 100%
Total size: 188.86kB (1.12Mbit/s)
Entry point 0x00000000
Image hello.exe loaded
grmon3> run
hello, world
CPU 0: Forced into debug mode
0x0001607c: 00100073 ebreak <_CPU_Fatal_halt+36>
CPU 1: Interrupted!
0x00011018: 10500073 wfi <_CPU_Thread_Idle_body+0>
grmon3>
To debug the compiled program you can insert break points, step and continue directly from the GRMON console.
Compilation symbols are loaded automatically by GRMON once you load the executable. An example is provided
below.
grmon3> load hello.exe
[...]
Total size: 188.86kB (1.12Mbit/s)
Entry point 0x00000000
Image hello.exe loaded
grmon3> bp Init
Software breakpoint 1 at <Init>
grmon3> run
Breakpoint 1 hit
0x00000118: 1141 addi sp, sp, -16 <Init+0>
grmon3> inst 5
TIME L P ADDRESS INSTRUCTION RESULT SYMBOL
593654 1 M 0000705a jalr ra, a5 [000000000000705C] _Thread_Handler+0x4e
593658 1 M 00007684 ld t1, 272(a0) [0000000000000118] _Thread_Entry_adaptor_numeric+0x0
593660 0 M 00007688 ld a0, 280(a0) [0000000000023128] _Thread_Entry_adaptor_numeric+0x4
593660 1 M 0000768c jalr zero, t1 [000000000000768E] _Thread_Entry_adaptor_numeric+0x8
593695 0 M 00000118 addi sp, sp, -16 [ BREAKPOINT ] Init+0x0
grmon3> step
0x4000013c: 4002e537 lui a0, 0x4002e <Init+0>
grmon3> inst 5
TIME L P ADDRESS INSTRUCTION RESULT SYMBOL
593660 0 M 00007688 ld a0, 280(a0) [0000000000023128] _Thread_Entry_adaptor_numeric+0x4
593660 1 M 0000768c jalr zero, t1 [000000000000768E] _Thread_Entry_adaptor_numeric+0x8
593695 0 M 00000118 ebreak [ BREAKPOINT ] Init+0x0
593728 0 M 00000118 addi sp, sp, -16 [0000000000029D70] Init+0x0
593729 0 M 0000011a sd s0, 0(sp) [0000000000029D70] Init+0x2

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 15 www.cobhamaes.com/gaisler
grmon3> reg
a0: 0000000040023128 t0: 7F7F7F7FFFFFFFFF s0: 0000000040021A48
a1: 0000000000000000 t1: 0000000040000118 s1: 0000000000000000
a2: 000000004001ECC8 t2: FFFFFFFFFFFFFFFF s2: 0000000000000000
a3: 000000000A010001 t3: 0000000000000000 s3: 0000000000000000
a4: 0000000000000000 t4: 0000000000000002 s4: 0000000000000000
a5: 0000000040007684 t5: 00000000000021ED s5: 0000000000000000
a6: 0000000021DAE500 t6: FFFFFFFFFFFFFFF0 s6: 0000000000000000
a7: 0000000021DAE500 s7: 0000000000000000
tp: 0000000000000000 s8: 0000000000000000
sp: 0000000000029D70 gp: 0000000000020800 s9: 0000000000000000
s10: 0000000000000000
mstatus: 0000000A00000008 mip: 000 mie: 800 s11: 0000000000000000
ra: 000000000000705C <_Thread_Handler+0x50>
pc: 000000000000011A sd s0, 0(sp) <Init+0x2>
grmon3> cont
hello, world
Forced into debug mode
0x0000c2ba: 9002 ebreak <_CPU_Fatal_halt+36>
grmon3>
Alternatively you can run GRMON with the -gdb command line option and then attach a GDB session to it.
5.6. RISC-V and NOEL-V integration with RTEMS
5.6.1. CSRs
RTEMS RISC-V executes in machine privilege mode only. The following is the set of CSRs which are accessed
by the kernel:
•mcause
•mepc
•mie
•mstatus
•mtvec
5.6.2. Clock tick
mtime is used for the RTEMS kernel clock service. It relies on the core local interrupt controller (clint).
Note that an RTEMS application can chose to not use the kernel clock service, in which case the the mtime
interrupt will not be enabled.
5.6.3. Exceptions
The only RISC-V exceptions handled by RTEMS is the mtime interrupt exception and external interrupts. All
other exceptions (interrupt and non-interrupt) will result in a kernel fatal. The fatal handler will print the current
processor state and then terminate execution.
Terminating execution is performed on NOEL-V by executing a ebreak.
5.6.4. NOEL-V BSP variants
The NOEL-V RTEMS BSP variants are similar to the RTEMS mainline BSP variants for RISC-V (rv64imac,
etc) available in the kernel source tree directory bsps/riscv/riscv/config.
The full list of BSP variants provided with the tool chain is:
•noel32i
•noel32im
•noel32imafd
•noel32imafd_smp

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 16 www.cobhamaes.com/gaisler
•noel32ima_smp
•noel64im
•noel64imafd
•noel64imafd_smp
•noel64ima_smp
BSP variants suffixed with _smp have SMP enabled in the kernel.
5.6.5. Console driver
NOEL-V BSP variants include support for the GRLIB APBUART device which is used as RTEMS console. The
GRLIB driver apbuart_termios.c is used. That is, the NOEL-V BSP and the LEON BSP:s use the same
console driver. Polling mode is used by default and the kernel can optionally be configured for interrupt console
UART.
5.6.6. Memory layout
All NOEL-V RTEMS BSP variants link the full application to RAM. The link address is the first address of RAM:
0x00000000. ROM is not used. MMU or PMP is not used by RTEMS.
5.6.7. Work area
The NOEL-V RTEMS BSP variants tries to detect the amount of RAM and sizing of the workspace (heap) at run-
time. This is done by investigating the stack pointer (sp) at entry to kernel.
• If sp equals 0at entry to the kernel, then the BSP assumes that a total of 12 MiB RAM is available.
• If sp is not equal to 0at entry to the kernel, then the BSP assumes that sp points to the top of RAM.
In both cases, the workspace (heap) is configured to use all RAM space ranging from end of the image to the end
of RAM. sp is normally initialized by GRMON when using the run command.
5.6.8. Symmetric Multiprocessing
RTEMS on NOEL-V supports Symmetric Multiprocessing (SMP). This works out-of-the-box with NOEL-V and
no RTEMS changes are needed for SMP, except for giving the option --enable-smp when configuring the
kernel. Some of the NOEL-V BSP variants in the binary kernel distribution are compiled with SMP support
(Section 5.6.4).
5.7. Device tree
5.7.1. Background
RTEMS relies on a device tree description of the target system to operate. It is used for locating peripheral devices
and other hardware configuration. On entry to the kernel, RTEMS assumes that a pointer to the device tree is
available in register a1. The RTEMS init code copies the device tree from the location pointed to by a1 to a
private buffer in RAM where it is later parsed during device discovery.
Whenbuilding an RTEMS applicationwith rtems-noel-1.0.4, a devicetree is not includedin the link image.
The benefit of this is that the same application binary can be used on different systems.
5.7.2. GRMON
GRMON is responsible for preparing the device tree binary file (.dtb) in RAM and pointing to it with a1.
Preparing and defining the device tree with GRMON is easiest done using the dtb command.
Then use the command run as normal to start an RTEMS application, or any other application expecting a device
tree:
Example 5.2. load and run a RAM image which expects a device tree
grmon3> dtb noel-xilinx-artya7.dtb
grmon3> load myprogram.elf
grmon3> run

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 17 www.cobhamaes.com/gaisler
5.7.2.1. Details
The following describes how to manually prepare GRMON and the processor for executing an RTEMS applica-
tion. It replicates the steps taken by the run command after it has been patched.
• The below procedure may change or may not be needed in future versions of GRMON or the RTEMS BSP.
1. Use the device tree compiler (dtc) to generate a device tree blob (.dtb) from a device tree source file ().
$ dtc board.dts > board.dtb
2. Tell GRMON about the the device tree blob .dtb file with the dtb command.
grmon3> dtb the.dtb
3. Load the application ELF file.
grmon3> load hello.exe
4. Start execution with the GRMON command run.
grmon3> run
5.8. Compiler options
The build examples above use Makefile fragments available in the tool chain installation directory and is provided
by the RTEMS kernel. An overview of this is given in the text file rtems-noel-1.0.4/kernel/share/
rtems5/make/README.
All GCC compiler options are described in the GCC User's Manual. Some of the commonly used options are
repeated below:
Table 5.1. Common GCC options for rtems-noel
-g generate debugging information - must be used for debugging with GDB
-msoft-float emulate floating-point - must be used if no FPU exists in the system
-march=rv64ima generate code with mul/div and atomic instructions
-O2 or -O3 optimize code maximum performance and minimal code size
5.9. Building the kernel
The source code for the RTEMS NOEL-V BSPs is available in the archive named rtems-noel-1.0.4-
src.tar.bz2.
Tobuildthekernel,firstextracttheNOEL-V RTEMS kernelsourcearchive,andthen use thefollowingcommands:
Example 5.3.
export THE_KERNPREFIX=/opt/my-rtems-noel
cd <kernel-source-dir>
./bootstrap
mkdir -p build
cd build
../configure \
--prefix=$THE_KERNPREFIX \
--target=riscv-rtems5 \
--enable-smp \
--enable-tests \
--enable-posix=yes \
--enable-rtemsbsp="noel32imafd_smp noel64imafd_smp"
make -j 4
make install
5.9.1. RTEMS test suite
Giving the kernel configure option --enable-tests will build the RTEMS kernel test suite, consisting of over
600 tests, together with the kernel. Most tests run correctly on NOEL-V. Cobham Gaisler is currently analyzing

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 18 www.cobhamaes.com/gaisler
if failing tests can be explained by general RTEMS issues, RISC-V issues in RTEMS, or because of the NOEL-
V integration.
5.10. Building the tool chain
The host tools can be built using the rtems-source-builder, as described at [RD-4]. A git patch file is included in
the binary distribution which adds additinoal multilibs. rtems-noel tools were built using this patch applied
on top of rtems-source-builder. The commit hash is specified in the README of the binary tool chain distribution.
An example on how to build the tool chain is provided below.
Example 5.4.
export THE_PREFIX=/opt/my-rtems-noel
export THE_RSB_REPO="git://git.rtems.org/rtems-source-builder.git"
export THE_RSB_COMMIT=5.1
export THE_RSB_PATCHES=/opt/rtems-noel-1.0.4/0001-noel-multilibs-for-gcc-9.3.0.patch
git clone $THE_RSB_REPO rsb
pushd rsb
git checkout -b noel $THE_RSB_COMMIT
git apply $THE_RSB_PATCHES --check
git am $THE_RSB_PATCHES
popd
pushd rsb/rtems
../source-builder/sb-set-builder --prefix=$THE_PREFIX 5/rtems-riscv
popd

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 19 www.cobhamaes.com/gaisler
6. Bare-metal cross-compiler
6.1. Overview
The Bare C Cross-Compiler (NCC) is a GNU-based cross-compilation system for NOEL-V processors. It allows
cross-compilation of C and C++ single-threaded applications. This section gives the reader a brief introduction
on how to use NCC together with the NOEL-ARTYA7-EX design. It will be demonstrated how to build an an
example program and run it on the NOEL-ARTYA7-EX using GRMON.
The NCC toolchain includes the GNU C/C++ cross-compiler 10.2.0, GNU Binutils, Newlib embedded C library,
the Bare-C run-time system with NOEL-V support and the GNU debugger (GDB). The toolchain can be down-
loaded from [RD-1] and is available for Linux host.
6.2. Installation
Extract the toolchain and add the bin directory to PATH. For example:
$ cd /opt
$ tar xf ncc-1.0.0-gcc.tar.bz2
$ PATH="$PATH:/opt/ncc-1.0.0-gcc/bin"
The rest of this chapter assumes that the toolchain has been installed and that riscv-gaisler-elf-gcc is available
in the PATH environment variable.
6.3. Compiling with NCC
The following command shows an example of how to compile a typical hello, world program with NCC.
$ cat hello.c
#include <stdio.h>
int main(void)
{
printf("hello, world\n");
return 0;
}
$ riscv-gaisler-elf-gcc -O2 -g hello.c -o hello.elf
It creates a program with the following characteristics:
• RV64IM instruction set
• linked to address 0.
• UART, TIMER, PLIC is probed using AMBA Plug&Play.
To build the same example targeting a 32-bit NOEL-V processor, use:
$ riscv-gaisler-elf-gcc -march=rv32im -mabi=ilp32 -O2 -g hello.c -o hello.elf
6.4. Compiler options
All GCC options are described in the gcc manual. Some of the most common options are:
Table 6.1. NCC's GCC compiler relevant options
-g generate debugging information - recommended for debugging with GDB
-march= Selects instruction set for code generation. See Section 6.5.
-mabi= Select ABI.
-O2 optimize for speed
-Os optimize for size
-Og optimize for debugging experience
6.5. Multilibs
The available multilibs are:

NOEL-ARTYA7-EX-QSG
December 2020, Version 1.2 20 www.cobhamaes.com/gaisler
Directory Options
---------------------------------------------------
rv32i/ilp32 -march=rv32i -mabi=ilp32
rv32im/ilp32 -march=rv32im -mabi=ilp32
rv32ima/ilp32 -march=rv32ima -mabi=ilp32
rv32imafd/ilp32d -march=rv32imafd -mabi=ilp32d
rv64ima/lp64 -march=rv64ima -mabi=lp64
rv64imafd/lp64d -march=rv64imafd -mabi=lp64d
---------------------------------------------------
The default multilib when (no march or mabi) is used corresponds to -march=rv64im -mabi=ilp64.
6.6. Running and debugging with GRMON
Once your application is compiled, connect to your NOEL-ARTYA7-EX with GRMON. The following log shows
how to load and run an application. Note that the console output is redirected to GRMON by the use of the -u
command line switch, so that the application standard output is forwarded to the GRMON console.
$ grmon -ftdi -u
GRMON3 LEON debug monitor v3.2.9 professional version
Copyright (C) 2020 Cobham Gaisler - All rights reserved.
For latest updates, go to http://www.gaisler.com/
Comments or bug-reports to [email protected]
[...]
grmon3> load hello.elf
00000000 .text 23.6kB / 23.6kB [===============>] 100%
00005E70 .data 2.7kB / 2.7kB [===============>] 100%
Total size: 26.29kB (803.58kbit/s)
Entry point 0x00000000
Image hello.elf loaded
grmon3> run
hello, world
CPU 0: Program exited normally.
Todebug the compiled program you can insert breakpoints, step andcontinue execution directly from the GRMON
console. Program symbols are loaded automatically by GRMON when you load the application. An example is
provided below.
grmon3> load hello.elf
00000000 .text 23.6kB / 23.6kB [===============>] 100%
00005E70 .data 2.7kB / 2.7kB [===============>] 100%
Total size: 26.29kB (806.59kbit/s)
Entry point 0x00000000
Image hello.elf loaded
grmon3> bp main
Software breakpoint 1 at <main>
grmon3> run
CPU 0: breakpoint 1 hit
0x00001928: b0102000 addi sp, sp, -16 <main+0>
grmon3> step
0x40001928: b0102000 mov 0, %i0 <main+4>
grmon3> step
0x4000192c: 11100017 sethi %hi(0x40005C00), %o0 <main+8>
grmon3> cont
hello, world
CPU 0: Program exited normally.
Alternatively you can run GRMON with the -gdb command line option and then attach a GDB session to it.