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Installing nRF Connect SDK
Carefully read the [Nordic nRF Connect SDK documentation] Documentation for installation instructions. At a bare minimum on a Linux host they boil down to the following steps:
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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:
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# 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:
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This example provides a CLI on the UART that can be accessed from Linux running on the N8:
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oot@solidsenseroot@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:
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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:
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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 |