embedded-trainings-2020/boards/dongle

dongle

Pre-made applications for the nRF52840 Dongle.

These applications will be used in the beginner workshop.

Hardware

LEDs

• The green LED (LD1) is connected to pin P0.6
• The red channel of the RGB LED (LD2) is connected to pin P0.8
• The green channel of the RGB LED (LD2) is connected to pin P1.9
• The blue channel of the RGB LED (LD2) is connected to pin P0.12

Both LEDs are mounted near the USB connector.

Buttons

• The Reset button is mounted sideways near the edge of the board that's opposite of the USB connector.
• The SW1 button is connected to pin P1.06. This round-ish button is right next to the RESET button but closer to the USB connector.

Changing the puzzle secret string

Create the secret string

Run the puzzlegen.rs program on the host to create a new secret string.

$ cargo new --bin puzzlegen

$ cp puzzlegen.rs puzzlegen/src/main.rs

$ cd puzzlegen
$ # or manually modify the Cargo.toml
$ cargo add rand

$ # update the plaintext in `src/main.rs`
$ cargo run

Take note of the output; it will look like this:

from: [116, 68, 123, 97, 47, 46, 90, 120, 34, 49, 59, 39, 50, 106, 71, 75, 108, 115, 81, 117, 69, 57, 76, 41, 100, 38, 93, 58, 78, 126, 70, 56, 84, 111, 113, 91, 89, 55, 40, 114, 122, 52, 61, 64, 45, 79, 67, 83, 48, 66, 63, 104, 43, 77, 44, 54, 98, 92, 94, 60, 62, 118, 87, 80, 95, 74, 65, 112, 109, 73, 110, 101, 53, 86, 33, 121, 42, 35, 85, 82, 105, 36, 37, 119, 125, 51, 96, 99, 88, 32, 103, 72, 107, 124, 102]
to: [81, 78, 109, 61, 120, 87, 125, 98, 100, 91, 97, 66, 57, 117, 49, 64, 48, 85, 75, 73, 92, 101, 83, 110, 62, 89, 35, 37, 93, 71, 123, 121, 60, 38, 115, 102, 59, 47, 108, 80, 58, 44, 86, 111, 41, 84, 96, 50, 51, 70, 43, 112, 79, 46, 113, 107, 106, 116, 65, 68, 69, 77, 105, 56, 103, 67, 40, 54, 99, 55, 45, 63, 34, 88, 119, 74, 94, 32, 114, 36, 95, 124, 118, 76, 126, 72, 82, 122, 33, 104, 90, 39, 42, 52, 53]
secret: "<p=-*Uh5&Ph6=PQ_z_6=Q_-Zh_-h&IPh?cj?>>?>h$IUQhL&P*Up&6w"

Generate puzzle ELF

$ git clone --branch dongle-puzzle https://github.com/japaric/embedded2020

$ cd embedded2020/firmware/apps

Find puzzle.rs in the embedded2020/firmware/apps/src/bin folder.

Update puzzle.rs with the FROM, TO and SECRET data that you got from puzzlegen

static FROM: &[u8] = &[
    116, 68, 123, 97, 47, 46, 90, 120, 34, 49, 59, 39, 50, 106, 71, 75, 108, 115, 81, 117, 69, 57,
    76, 41, 100, 38, 93, 58, 78, 126, 70, 56, 84, 111, 113, 91, 89, 55, 40, 114, 122, 52, 61, 64,
    45, 79, 67, 83, 48, 66, 63, 104, 43, 77, 44, 54, 98, 92, 94, 60, 62, 118, 87, 80, 95, 74, 65,
    112, 109, 73, 110, 101, 53, 86, 33, 121, 42, 35, 85, 82, 105, 36, 37, 119, 125, 51, 96, 99, 88,
    32, 103, 72, 107, 124, 102,
];

static TO: &[u8] = &[
    81, 78, 109, 61, 120, 87, 125, 98, 100, 91, 97, 66, 57, 117, 49, 64, 48, 85, 75, 73, 92, 101,
    83, 110, 62, 89, 35, 37, 93, 71, 123, 121, 60, 38, 115, 102, 59, 47, 108, 80, 58, 44, 86, 111,
    41, 84, 96, 50, 51, 70, 43, 112, 79, 46, 113, 107, 106, 116, 65, 68, 69, 77, 105, 56, 103, 67,
    40, 54, 99, 55, 45, 63, 34, 88, 119, 74, 94, 32, 114, 36, 95, 124, 118, 76, 126, 72, 82, 122,
    33, 104, 90, 39, 42, 52, 53,
];

// store the secret rather than the plaintext -- otherwise `strings $elf` will reveal the answer
static SECRET: &[u8] = b"<p=-*Uh5&Ph6=PQ_z_6=Q_-Zh_-h&IPh?cj?>>?>h$IUQhL&P*Up&6w";

Build the program; this will produce an ELF file called puzzle (no file ending).

$ cargo build --bin puzzle --release

Copy this ELF file from embedded2020/firmware/target/thumbv7em-none-eabi/release to embedded-trainings-2020/boards/dongle

Test the produced puzzle file:

• flash it onto a dongle using nrfdfu puzzle. The green LED on the dongle should turn on
• run cargo xtask serial-term; you should see the following output. deviceid will be different

deviceid=d90eedf1978d5fd2 channel=25 TxPower=+8dBm app=puzzle

• run the radio-puzzle-solution program on a DK; it should be able to decrypt the new secret
• run cargo xtask change-channel <some number between 11 and 26> to test changing the Dongle's radio channel
• modify and re-run the radio-puzzle-solution program on a DK to solve the puzzle using a the channel you set in the previous step

Generate puzzle-nousb-*

The procedure is similar to the one for generating the puzzle ELF file. The differences are:

• you build puzzle-nousb.rs in the embedded2020 repository and copy embedded2020/firmware/target/thumbv7em-none-eabi/release/puzzle-nousb over
• you also need to change const CHANNEL in puzzle-nousb.rs
• you need to produce one ELF file per hard-coded radio channel.

Also test these nousb ELF files. Note that the green LED won't turn on when the dongle restarts! The green LED will toggle when a new packet is received and the blue LED will turn on when the decoded secret is received. Also, cargo xtask change-channel won't work with the nousb variants so you can skip that test.

References

• nRF52840 Dongle section on Nordic Semiconductor's info center