The nRF52840 Dongle is a platform based around the nRF52840, an SoC with an ARM Cortex-M4 and a BLE radio. The kit is uses a USB key form factor and includes 1 button, 1 red LED and 1 RGB LED.
To program the nRF52840 Dongle with Tock, you will need a JLink JTAG device and the appropriate cables. An example setup is:
Then, follow the Tock Getting Started guide
JTAG is the preferred method to program. The development kit has the JTAG pins exposed either through the half-moons pads or, below the PCB, on a Tag-Connect TC2050 connector footprint. You need to install JTAG software.
Once you have all software installed, you should be able to simply run make flash in this directory to install a fresh kernel.
You can program an application via JTAG using tockloader:
$ cd libtock-c/examples/<app>
$ make
$ tockloader install --jlink --board nrf52dkSee the nrf52dk README for information about debugging the nRF52840 Dongle.