Problem Flashing nrf52 chip using Openocd

Question

I have a custom nrf52 chip on a pcb with swd pins exposed. I have cloned and installed the latest openocd from https://github.com/ntfreak/openocd. The latest version includes all the latest pathes for the nrf52 chip, so no need for any additional changes as suggested in many older guides online. I am able to connect to the chip using ST-LinkV2. when connected I can read and write memory locations using mdw and mdb. I can also run some basic openocd commands like dump_image e.t.c, which confirms that the setup is good. But halt and program commannds always lead to errors like:

JTAG failure -4
JTAG failure -4
JTAG failure -4
JTAG failure -4
JTAG failure -4
JTAG failure -4
target halted due to debug-request, current mode: Thread 
xPSR: 00000000 pc: 00000000 msp: 00000000
jtag status contains invalid mode value - communication failure
Polling target nrf52.cpu failed, trying to reexamine
Examination failed, GDB will be halted. Polling again in 100ms
Previous state query failed, trying to reconnect
jtag status contains invalid mode value - communication failure
Polling target nrf52.cpu failed, trying to reexamine

if I try to use flash image_write I get the error,

JTAG failure
Error setting register
error starting target flash write algorithm
Failed to enable read-only operation
Failed to write to nrf52 flash
error writing to flash at address 0x00000000 at offset 0x00000000
in procedure 'dap'
jtag status contains invalid mode value - communication failure
Polling target nrf52.cpu failed, trying to reexamine

I have read different guides online, and one of the possible solutions involves the APPPROTECT register which has to be disabled to enable any writes to flash. APP_PROTECT, But the dap commmand which is supposed to help us access this bit,

dap apreg 1 0x04 0x01

returns an error:

invalid subcommand apreg 1 0x04 0x01

Please, I will like to know if anyone has had success programming a new empty nrf52 chip with the stlink-v2 and the steps which are necessary, or if any one has encountered similar problems. Thanks.

Here is my config file:

#nRF52832 Target
source [find interface/stlink.cfg]

transport select hla_swd

source [find target/nrf52.cfg]

#reset_config srst_nogate connect_assert_srst

Have you searched Nordic dev zone for this? devzone.nordicsemi.com/f/nordic-q-a/21415/… — Catsunami

matthew matthew · Accepted Answer · 2019-01-25T20:43:16

I solved the "protected nRF52" chip problem this way, on Windows, using a Particle.io Debugger https://store.particle.io/products/particle-debugger setup to program nRF52 chips from Arduino as described in https://www.forward.com.au/pfod/BLE/LowPower/index.html

Note: The recovery process described here does NOT need Arduino to be installed

Download OpenOCD-20181130.7z pre-compiled openocd for windows from http://gnutoolchains.com/arm-eabi/openocd/

The latest version of openocd src on https://github.com/ntfreak/openocd should also work as it includes the apreg cmd in target\arm_adi_v5.c

unzip, open cmd prompt to unzip dir, enter cmd

bin\openocd.exe -d2 -f interface/cmsis-dap.cfg -f target/nrf52.cfg

response

Info : auto-selecting first available session transport "swd". To override use '
transport select <transport>'.
adapter speed: 1000 kHz
cortex_m reset_config sysresetreq
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : CMSIS-DAP: SWD  Supported
Info : CMSIS-DAP: FW Version = 1.10
Info : CMSIS-DAP: Interface Initialised (SWD)
Info : SWCLK/TCK = 1 SWDIO/TMS = 1 TDI = 0 TDO = 0 nTRST = 0 nRESET = 1
Info : CMSIS-DAP: Interface ready
Info : clock speed 1000 kHz
Info : SWD DPIDR 0x2ba01477
Error: Could not find MEM-AP to control the core
Info : Listening on port 3333 for gdb connections

Open telnet program eg teraTerm and connect to localhost on port 4444, i.e. 127.0.0.1 telnet port 4444

cmd window shows

Info : accepting 'telnet' connection on tcp/4444

in telnet (i.e. teraTerm) type

nrf52.dap apreg 1 0x04

returns 0 <<< chip protected then

nrf52.dap apreg 1 0x04 0x01

then

nrf52.dap apreg 1 0x04

returns 1 << chip un-protected

then power cycle board

Can now use arduino ide to flash softdevice and code low power BLE

Problem Flashing nrf52 chip using Openocd

4 Answers