How to Fix Your Particle Mesh Board Using J-link

Jared Wolff · 2019.8.6· 4 Minute Read · particle

Intro image

If you anything like me, you break stuff. (Like.. all the time.)

This quick tutorial is about how to un-brick a Particle Mesh board using J-Link.

This method may seem scary. It sure was when I started! The good thing is that anything done wrong here is reversible.

Let’s get going!

Prerequisites

  1. You will need jlinkexe installed if you haven’t already. Go here and find the J-link Software and Documentation Pack.
  2. You’ll need to download the latest Nordic softdevice. As of this writing it’s s140_nrf52_6.0.0_softdevice.hex. It’s also the one that Particle is currently using.
  3. You’ll also need a 10-pin ribbon cable that is compatible. If you don’t have one, a reasonable one can be found at Adafruit.

Now let’s un-bork you board!

  1. Connect nRF52 dev kit (or similar) to your computer

  2. Connect the 10pin ribbon cable to the Debug out connector on the NRF52 dev kit.

    Setup

  3. Connect to jlinkexe using the following command

     jlinkexe -device nRF52 -if SWD -speed 4000 -autoconnect 1
    

    If all is well, jlinkexe will connect and the output will look something like this:

     Jareds-MacBook-Pro:nrfjprog.sh jaredwolff$ jlinkexe -device nRF52 -if SWD -speed 4000 -autoconnect 1
     SEGGER J-Link Commander V6.40b (Compiled Jan 22 2019 11:31:00)
     DLL version V6.40b, compiled Jan 22 2019 11:30:49
    
     Connecting to J-Link via USB...O.K.
     Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Jan  7 2019 14:07:15
     Hardware version: V1.00
     S/N: 682978319
     VTref=3.300V
     Device "NRF52" selected.
    
    
     Connecting to target via SWD
     Found SW-DP with ID 0x2BA01477
     Found SW-DP with ID 0x2BA01477
     Scanning AP map to find all available APs
     AP[2]: Stopped AP scan as end of AP map has been reached
     AP[0]: AHB-AP (IDR: 0x24770011)
     AP[1]: JTAG-AP (IDR: 0x02880000)
     Iterating through AP map to find AHB-AP to use
     AP[0]: Core found
     AP[0]: AHB-AP ROM base: 0xE00FF000
     CPUID register: 0x410FC241. Implementer code: 0x41 (ARM)
     Found Cortex-M4 r0p1, Little endian.
     FPUnit: 6 code (BP) slots and 2 literal slots
     CoreSight components:
     ROMTbl[0] @ E00FF000
     ROMTbl[0][0]: E000E000, CID: B105E00D, PID: 000BB00C SCS-M7
     ROMTbl[0][1]: E0001000, CID: B105E00D, PID: 003BB002 DWT
     ROMTbl[0][2]: E0002000, CID: B105E00D, PID: 002BB003 FPB
     ROMTbl[0][3]: E0000000, CID: B105E00D, PID: 003BB001 ITM
     ROMTbl[0][4]: E0040000, CID: B105900D, PID: 000BB9A1 TPIU
     ROMTbl[0][5]: E0041000, CID: B105900D, PID: 000BB925 ETM
     Cortex-M4 identified.
     J-Link>
    
  4. Next let’s erase the whole chip + write the softdevice.

     h
     w4 4001e504 2
     w4 4001e50c 1
     sleep 100
     r
     h
     w4 4001e504 1
     loadfile /path/to/s140_nrf52_6.0.0_softdevice.hex
     r
    

    Let’s go through each command:

    h is to halt the chip from executing code

    w4 4001e504 2 is writing to the magic control register to allow erase to flash

    w4 4001e50c 1 is the command to erase the whole chip

    r is to reset the device and h is to halt again

    w4 4001e504 1 is to allow writes to flash so we can write the soft device

    loadfile loads the file into flash. If it’s a hex file we only need one parameter

    we finally reset with r

  5. Next let’s write the bootloader

     h
     w4 4001e504 1
     loadfile /path/to/[email protected] 0xf4000
     r
     h
     w4 4001e504 2
     w4 4001e514 1
     w4 4001e504 1
     w4 10001014 0xf4000
     w4 4001e504 0
     r
     g
     exit
    

    Let’s break down some of the new commands here:

    loadfile writes a binary file. The address parameter is required. We use 0xf4000 because that is the starting address for the bootloader.

    After loadfile we want to make sure the processor is stopped with r and h

    w4 4001e504 2 enables an erase but this time we’ll only erase the UICR. The UICR is a non-volatile part of memory used to track reset information, boot vectors, etc. We erase it first with w4 4001e514 1

    Then, using w4 10001014 0xf4000, we write the bootloader address to 10001014. That way, the NRF52840 boots to the correct location!

    w4 4001e504 0 disables write mode.

    We finish up with a r g and exit. This will reset, start execution and exit from jlinkexe We’re done here!

At the end of step 5, your device should be blinking yellow. You can follow the standard procedure using particle flash

The easier alternative

I’ve also modified a shell script written a long time ago before Nordic had a stable command line tool for OSX.

  1. Clone git clone [[email protected]](mailto:[email protected]):jaredwolff/nrfjprog.sh.git
  2. Change to that directory
  3. Run ./nrfjprog.sh --flash-softdevice /path/to/s140_nrf52_6.0.0_softdevice.hex
  4. Then, run ./nrfjprog.sh --flash-bootloader-bin /path/to/[email protected] 0xf4000
  5. The device should be blinking yellow. Next, let’s program the system part:particle flash --usb /path/to/[email protected]
  6. Finally, lets flash Tinker to make sure everything works!particle flash --usb /path/to/[email protected]

Note: you can substitute the deviceOS version that i’ve used above. Just make sure they’re the same.

Conclusion

That’s it for this quick tutorial. Hope you found it useful!

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