Running

In order to finally run NuttX on your board, you first have to flash the NuttX binary. As an easy start, it is recommended that you choose a well supported board which also integrates the debugger/programmer in the board itself exposed via USB connector.

A good choice is a Nucleo or Discovery board from ST Microelectronics, as there is a wide choice of suported boards for the STM32 architecture in NuttX. Also, these boards expose an UART port over the USB connection which allows you to interact with NuttX via the interactive console without any extra hardware. For the purposes of this guide, we will use the Nucleo F103RB board.

Flashing

There are various tools you can use to flash the NuttX binary to your Nucleo board. One common option is to use openocd which supports a large number of programmers and target microcontrollers.

To install the stable version of openocd you can do:

$ apt install openocd

Todo

add instructions for other platforms

You should note that openocd project has not made stable releases for long time and support for newer hardware will probably be only available in the latest Git version. To install it you should:

$ git clone git://git.code.sf.net/p/openocd/code openocd
$ cd openocd
$ ./bootstrap
$ ./configure --prefix install/
$ make install

The resulting installation will be under openocd/install. You can add openocd/install/bin to your PATH.

Now, to flash the binary to your board, connect the USB cable and do:

$ cd nuttx/
$ openocd -f interface/st-link-v2.cfg -f target/stm32f1x.cfg -c 'init' \
  -c 'program nuttx/nuttx.bin verify reset' -c 'shutdown'

Access NuttShell

Once you flash your board, it will reset and offer a prompt over the serial console. With the Nucleo board, you can simply open the terminal program of your choice where you will see the nsh> prompt:

$ picocom -b 115200 /dev/ttyUSB0

Debugging

Using openocd you can also debug NuttX. To do so, first run:

$ openocd -f interface/st-link-v2.cfg -f target/stm32f1x.cfg

which will start a GDB server. Then, start gdb as:

$ cd nuttx/
$ gdb-multiarch nuttx/nuttx

Inside gdb console, connect to the openocd server with:

(gdb) target extended-remote :3333

You can debug using standard gdb commands.

Advanced Debugging with JTAG

If your board does not have an embedded programmer and uses JTAG connector instead, things are a bit different. This guide assumes you have a JTAG hardware debugger like a Segger J-Link. JTAG is a set of standards that let you attach a hardware device to your embedded board, and then remotely control the CPU. You can load code, start, stop, step through the program, and examine variables and memory.

  1. Attach the Debugger Cables

  2. Start the Debugger

    Refer to your JTAG debugger’s documentation for information on how to start a GDB Server process that gdb can communicate with to load code and start, stop, and step the embedded board’s CPU. Your command line may be different from this one.

    $ JLinkGDBServer -device ATSAMA5D27 -if JTAG -speed 1000 -JTAGConf -1,-1

  3. Launch the GNU Debugger

    In another terminal window, launch the GDB. In the case of this guide, this came with the ARM Embedded GNU Toolchain we downloaded in the Install step.

    $ cd nuttx/
$ gdb-multiarch nuttx/nuttx

  4. Set gdb to talk with the J-Link

    (gdb) target extended-remote :2331

  5. Reset the board

    (gdb) mon reset

  6. You may need to switch to the serial console to hit a key to stop the board from booting from its boot monitor (U-Boot, in the case of the SAMA5 boards from Microchip).

  7. Halt the board

    (gdb) mon halt

  8. Load nuttx

    (gdb) load nuttx
`/home/adamf/src/nuttx-sama5d36-xplained/nuttx/nuttx' has changed; re-reading symbols.
Loading section .text, size 0x9eae4 lma 0x20008000
Loading section .ARM.exidx, size 0x8 lma 0x200a6ae4
Loading section .data, size 0x125c lma 0x200a6aec
Start address 0x20008040, load size 654664
Transfer rate: 75 KB/sec, 15587 bytes/write.
(gdb)

  9. Set a breakpoint

    (gdb) breakpoint nsh_main

  10. Start nuttx

    (gdb) continue
Continuing.

Breakpoint 1, nsh_main (argc=1, argv=0x200ddfac) at nsh_main.c:208
208        sched_getparam(0, &param);
(gdb) continue
Continuing.

Debugging Shortcuts

Note that you can abbreviate gdb commands, info b is a shortcut for information breakpoints; c works the same as continue, etc.

Next up is Configuring.