SolidSense N8 nRF Connect SDK Example

This document gives instructions for using Nordic nRF Connect SDK for programming the 802.15.1 radio on SolidSense N8.

Instructions herein were tested on SolidRun Yocto BSP for i.MX8, Scarthgap release.

Installing nRF Connect SDK

Carefully read the nRF Connect SDK Documentation for installation instructions. At a bare minimum on a Linux host they boil down to the following steps:

Install nrfutil cli application
Install Toolchain using nrfutil
Download SDK Sources using nrfutil
Generate CMake Target

install -v -m755 -o root -g root ~/Downloads/nrfutil /usr/local/bin/
nrfutil install sdk-manager
nrfutil sdk-manager toolchain install --ncs-version v2.9.1

nrfutil sdk-manager toolchain launch --ncs-version v2.9.1  --shell
west init -m <https://github.com/nrfconnect/sdk-nrf> --mr v2.9.1 v2.9.1
cd ~/ncs/v2.9.1
west update
west zephyr-export

Enter Development Environment

This step should be repeated when launching a new terminal session:

nrfutil sdk-manager toolchain launch --ncs-version v2.9.1  --shell
cd ~/ncs/v2.9.1
source zephyr/zephyr-env.sh

cd <your-workspace>

Define Custom Board

Ultimately defining the SolidSense N8 as a board in Zephyr would be nice but is left as an exercise for the future.

Instead it is possible to reuse the already supported "nrf52833dk" board which is similar enough.

A device-tree overlay should be added to the application process with customer- and SolidRun-specific changes: <app-source>/boards/nrf52833dk_nrf52833.overlay:

/*
 * Copyright (c) 2025 Josua Mayer <josua@solid-run.com>
 */

&button0 {
        /* remap to GPIO18 (BT_RST#) from application processor */
	gpios = <&gpio1 2 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
};

&uart0 {
	/* Note: Flow-Control should be disabled: hw-flow-control; */
};

Thread CLI Sample

nRF Connect SDK provides a Thread example application with CLI interface on the MCU UART.
It can be ported to the SolidSense N8 as follows:

Copy example from nRF Connect SDK:
cd <your-workspace> cp -r ~/ncs/v2.9.1/nrf/samples/openthread/cli ./ot-cli-app cd ot-cli-app # optionally initialise version control git init . git add . git commit
Add Board configuration:
Create a new device-tree overlay at boards/nrf52833dk_nrf52833.overlay with the content described above.
Compile
west build -b nrf52833dk/nrf52833
The resulting application binary is found at build/ot-cli-app/zephyr/zephyr.bin:
ls -ln ./build/ot-cli-app/zephyr/zephyr.bin -rwxr-xr-x 1 1001 100 461524 7. Apr 18:38 ./build/ot-cli-app/zephyr/zephyr.bin

Program Application

The generated zephyr.bin file comes without separate bootloader and can be installed at offset 0 to the MCU flash.
The programming procedure utilizes SWD interface with OpenOCD.

OpenOCD uses a server-client architecture, it is therefore recommended to operate at least two concurrent terminals to the board, e.g. one UART Console and one SSH, or 2x SSH.
Open a third console for interactive debugging to monitor the UART between MCU and Linux.

Take MCU out of reset

The MCU may be kept in reset by GPIO1_IO5 of the Host. Release it:

# check status of control gpios (reset, power)
gpioget -c /dev/gpiochip0 5 6
"5"=inactive "6"=active

# release reset
gpioset -c /dev/gpiochip0 5=1

Start OpenOCD

A suitable configuration file for SolidSense N8 with FWM7BLZ22W MCU is provided below:

source [find interface/imx-native.cfg]
transport select swd
set WORKAREASIZE 0
source [find target/nrf52.cfg]
imx_gpio_peripheral_base 0x30200000
imx_gpio_speed_coeffs 50000 50
imx_gpio_swd_nums 14 15

The above is included by default in our Yocto BSP at /etc/openocd.cfg, but can be created on the fly as needed.

On the first console start the openocd server:

root@solidsense-n8:~# openocd --file /etc/openocd.cfg
Open On-Chip Debugger 0.12.0+dev-00150-g91bd43134-dirty (2025-04-07-18:00)
Licensed under GNU GPL v2
For bug reports, read
        <http://openocd.org/doc/doxygen/bugs.html>
imx_gpio GPIO nums: swclk = 14, swdio = 15
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : imx_gpio GPIO JTAG/SWD bitbang driver
Info : imx_gpio mmap: pagesize: 4096, regionsize: 131072
Info : clock speed 1000 kHz
Info : SWD DPIDR 0x2ba01477
Info : [nrf52.cpu] Cortex-M4 r0p1 processor detected
Info : [nrf52.cpu] target has 6 breakpoints, 4 watchpoints
Info : starting gdb server for nrf52.cpu on 3333
Info : Listening on port 3333 for gdb connections

Program MCU Flash

First the generated zephyr.bin file must be copied to the SolidSense N8 filesystem, e.g. at /root/zephyr.bin.

While openocd is running on the first console, use the second console for connecting with telnet:

root@solidsense-n8:~# telnet 127.0.0.1 4444
Connected to 127.0.0.1

Entering character mode
Escape character is '^]'.

Open On-Chip Debugger
> targets
    TargetName         Type       Endian TapName            State
--  ------------------ ---------- ------ ------------------ ------------
 0* nrf52.cpu          cortex_m   little nrf52.cpu          running

Halt the processor, erase flash and program zephyr.bin:

> halt
[nrf52.cpu] halted due to debug-request, current mode: Thread
xPSR: 0x41000000 pc: 0x0002083e psp: 0x20007e20
> nrf5 mass_erase
Mass erase completed.
> program /root/zephyr.bin 0x0000
[nrf52.cpu] halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0xfffffffe msp: 0xfffffffc
** Programming Started **
Adding extra erase range, 0x00070ad4 .. 0x00070fff
not enough working area available(requested 34)
no working area available, falling back to slow memory writes
** Programming Finished **

Programming may take a minute without progress indication.

Finally the MCU can be reset to restart execution.
It is however recommended to open /dev/ttymsxc3 and monitor the MCU UART before reset:

> reset
shutdown command invoked

Open MCU UART Console

This example provides a CLI on the UART that can be accessed from Linux running on the N8:

root@solidsense-n8:~# microcom -s 115200 /dev/ttymxc3

uart:~$ *** Booting nRF Connect SDK v2.9.1-60d0d6c8d42d ***
*** Using Zephyr OS v3.7.99-ca954a6216c9 ***
help
Please press the <Tab> button to see all available commands.
You can also use the <Tab> button to prompt or auto-complete all commands or its subcommands.
You can try to call commands with <-h> or <--help> parameter for more information.

Shell supports following meta-keys:
  Ctrl + (a key from: abcdefklnpuw)
  Alt  + (a key from: bf)
Please refer to shell documentation for more details.

Available commands:
  clear    : Clear screen.
  device   : Device commands
  devmem   : Read/write physical memory
             Usage:
             Read memory at address with optional width:
             devmem <address> [<width>]
             Write memory at address with mandatory width and value:
             devmem <address> <width> <value>
  gpio     : GPIO commands
  help     : Prints the help message.
  history  : Command history.
  kernel   : Kernel commands
  ot       : OpenThread subcommands
             Use "ot help" to get the list of subcommands
  rem      : Ignore lines beginning with 'rem '
  resize   : Console gets terminal screen size or assumes default in case the
             readout fails. It must be executed after each terminal width change
             to ensure correct text display.
  retval   : Print return value of most recent command
  shell    : Useful, not Unix-like shell commands.
uart:~$

microcom can be exited pressing ctrl+x.

Note: The MCU may be kept in reset by GPIO1_IO5 of the Host. Release it if needed: gpioset -c /dev/gpiochip0 5=1

Recovery after bad programming

It is possible to get the mcu into a locked state where openocd reports an “unknown” state, see lines 13 following:

root@solidsense-n8:~# openocd -f /etc/openocd.cfg 
Open On-Chip Debugger 0.12.0+dev-00150-g91bd43134-dirty (2025-04-07-18:10)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
imx_gpio GPIO nums: swclk = 14, swdio = 15
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : imx_gpio GPIO JTAG/SWD bitbang driver
Info : imx_gpio mmap: pagesize: 4096, regionsize: 131072
Info : clock speed 1000 kHz
Info : SWD DPIDR 0x2ba01477
Error: [nrf52.cpu] Could not find MEM-AP to control the core
****** WARNING ******
nRF52 device has AP lock engaged (see UICR APPROTECT register).
Debug access is denied.
Use 'nrf52_recover' to erase and unlock the device.

Warn : target nrf52.cpu examination failed
Info : starting gdb server for nrf52.cpu on 3333
Info : Listening on port 3333 for gdb connections

Recovery from this state is possible by nrf52_recover command:

Open On-Chip Debugger
> targets
    TargetName         Type       Endian TapName            State       
--  ------------------ ---------- ------ ------------------ ------------
 0* nrf52.cpu          cortex_m   little nrf52.cpu          unknown
> nrf52_recover
Waiting for chip erase...
nrf52.cpu device has been successfully erased and unlocked.
[nrf52.cpu] Cortex-M4 r0p1 processor detected
[nrf52.cpu] target has 6 breakpoints, 4 watchpoints
[nrf52.cpu] clearing lockup after double fault
Polling target nrf52.cpu failed, trying to reexamine
[nrf52.cpu] Cortex-M4 r0p1 processor detected
[nrf52.cpu] target has 6 breakpoints, 4 watchpoints
> targets
    TargetName         Type       Endian TapName            State       
--  ------------------ ---------- ------ ------------------ ------------
 0* nrf52.cpu          cortex_m   little nrf52.cpu          halted
> nrf5 mass_erase
nRF52833-xxAA(build code: A0) 512kB Flash, 128kB RAM
Mass erase completed.
> exit