Reprogramming the PineTime

Introduction

The PineTime Dev Kit comes with the back not glued down to allow it to be easily reprogrammed, however the kit does not include an hardware programmer/debugger.

There is a bewildering variety of different hardware programmers available but whatever programmer you have there are only a few tasks you will have to learn about:

• Unlock the device
• Upload new software
• Run a debugger

Unlocking the device is a one-time action that is needed to enable to debug port and provide full access to the device. Unlocking the device will erase all existing software from the internal flash.

nrfjprog

The following steps have been tested with the Segger JLink embedded in the NRF52-DK development board.

Hookup

Connect the Pinetime SWD pins to the debugger (P20 on NRF52-DK)

Pintime	JLink
GND	GND
SWDCLK	SWDCLK
SWDIO	SWDIO
VCC (3.3V)	VTG (target detect)

Unlocking the FLASH

Unlocking the device and erase the memory.

You need to execute this step only once, to remove the read protection on the memory. Note that it will erase the whole flash memory of the MCU! :

nrfjprog -f NRF52 --recover

Uploading new software

1. Program the BLE softdevice (if needed by the firmware). Replace PATH_TO_NRF_SDK by the path where you unzipped the NRF52 SDK :

nrfjprog -f NRF52 --program /PATH_TO_NRF_SDK/components/softdevice/s132/hex/s132_nrf52_6.1.1_softdevice.hex --sectorerase

2. Program the firmware (replace firmware.hex by the actual filename of the firmware):

nrfjprog -f NRF52 --program firmware.hex --sectorerase

3. Reset and run the new firmware:

nrfjprog -f NRF52 --reset

OpenOCD

Adapters

These examples allow you to use telnet to issue futher commands to the devkit. Using them you can connect to 127.0.0.1 (localhost) port 4444 using telnet and invoke OpenOCD commands. GDB should also be available on port 3333.

CMSIS-DAP

Issue this command to initialize a connection to the devkit:

openocd \
   -c 'source [find interface/cmsis-dap.cfg]' \
   -c 'transport select swd' \
   -c 'source [find target/nrf52.cfg]' \
   -c 'init'

JLink

Start OpenOCD:

openocd \
   -c 'interface jlink' \
   -c 'transport select swd' \
   -c 'source [find target/nrf52.cfg]' \
   -c 'init'

Raspberry Pi

openocd \
   -c 'interface bcm2835spi' \
   -c 'bcm2835spi_speed 31200' \
   -c 'source [find target/nrf52.cfg]' \
   -c 'init'

STLink

Complete this subsection if you have gotten it to work

Unlocking the device

If you need to disable access port protection then you can do this using the following commands below.

This can be done from the telnet connection, just use telnet localhost 4444.

Note: Unlocking the device to remove access port protection will erase the contents of flash.

 telnet localhost 4444
   Trying 127.0.0.1...
   Connected to localhost.
   Escape character is '^]'.
   Open On-Chip Debugger
   > nrf52.dap apreg 1 0x04
   0x00000000
   > nrf52.dap apreg 1 0x04 0x01
   > nrf52.dap apreg 1 0x04
   0x00000001

(If the nrf52.dap command cannot be found, try just dap instead.)

Uploading new software

Just issue this command, replace code.hex with your own (and cmsis-dap.cfg with an appropriate adapter).

 openocd \
     -c 'source [find interface/cmsis-dap.cfg]' \
     -c 'transport select swd' \
     -c 'source [find target/nrf52.cfg]' \
     -c 'init' \
     -c 'nrf5 mass_erase' \
     -c 'program code.hex verify' \
     -c 'reset' \
     -c 'exit'

Black Magic Probe

BlackMagic Probe is an JTAG/SWD adapter with open-source firmware, allowing for it to be ported to a multitude of different boards. One of it's defining features is lack of need for intermediate software such as OpenOCD - one would just need to connect to the GDB server running on the chip and proceed with debugging. For more information, refer to wiki.

Native adapters

The native adapters are the official Black Magic family of debug adapters, including the original Black Magic Probe and the Black Magic Probe Mini. By buying the official hardware you are supporting the continued development of the Black Magic Probe software.

Providing your native adapter is running up-to-date firmware then it can be used to program your PineTime.

STM32 (Blue Pill)

It is possible to flash a popular development board based on STM32F103C8T6 microcontroller, known as Blue Pill, to make a BlackMagic Probe device. For example, one may follow instructions in forum post or gist (mac os). Also, it is possible to use SWD pins on the board to flash other devices, instead using arbitrary pins on the board itself. See this link for more detals.

Other hardware

The Black Magic Probe firmware can be run on a variety of host devices. See BMP Debugger Hardware for more information.

Using the BMP to flash the PineTime

Refer to the BMP wiki for the full description of commands. Overall, the process on Linux is like following. (/dev/ttyBmpGdb is a symlink created by the udev rule). It's useful to create a gdb script file (or .gdbinit) with following commands:

 target extended-remote /dev/ttyBmpGdb
 monitor swdp_scan
 attach 1
 file %firmware file%

Then one may use load command to flash the firmware, compare-sections to verify the upload, or monitor erase_mass to erase the firmware.

Then, proceed with debugging as normal.

External links and additional tutorials

• https://github.com/jlukanc1/pinetime-boot-flasher
• https://blog.aegrel.ee/absniffer-cmsis-dap-sniffer.html
• https://blog.dbrgn.ch/2020/5/16/nrf52-unprotect-flash-jlink-openocd/
• https://medium.com/@ly.lee/openocd-on-raspberry-pi-better-with-swd-on-spi-7dea9caeb590
• https://medium.com/@ly.lee/build-and-flash-rust-mynewt-firmware-for-pinetime-smart-watch-5e14259c55