JellingStone

This repository is part of the Fieldtracks project, which aims at creating a tracking system to be used in field exercises by relief organizations.

Building

Please make yourself comfortable with ESP-IDF. JellingStone based on ESP-IDF a more-or-less standard way. It is built like other ESP-IDF Applications:

git clone https://github.com/FieldTracks/JellingStone.git

Finally run make flash to compile the project and flash it to an attached ESP32. Debug output can be watched with make monitor (or run them together with make flash monitor).

Flashing wifi and mqtt credentials to the ESP32

This will not run automatically during make flash.

1. Copy nvs_data.csv.example to nvs_data.csv
2. Edit the credentials
3. Run ./flash_nvs

Running JellingStone

The current design is designed to run on ESP32-WROOM dev-boards having a blue and a read LED. LED status indication:

• red (solely): Problems starting the APP. Jelling-Stone is not Active
• red + blue blinking
  • 1 Hz: Booting, no WLAN connection
  • 5 Hz: IP connection, no MQTT connection
  • 1 Hz / 5 Hz oscillating: Unrecoverable error occurred. Check monitor log
  • Short "twinkle": Report is submitted over MQTT
• red + blue: Device is operating (i.e. WLAN + MQTT connection, BLE is scanning and beaconing)

MQTT messages

SCAN report

Topic: JellingStone/scan/<MAC of BLE>

Header

Byte	Description
0	0x01 (Version), reserved: 0x7B for JSON Payloads
1-4	Report-ID / 32-Bit timestamp (seconds since Unix-epoch), Big-Endian / Network Byte Order
5	Message sequence number (signed), unique per report, starts at 0x01 in each report, incremented per message, a negative number marks final one, e.g. 0xFF (-1), if there's just one message
6	unsigned, number of beacon data segments in this message (report has more, if and only if there are more messages)
7 - 1100	0...255 (up to 255) segments of beacon data

Beacon Data segment

Byte	Description
0	Type and length of Beacon ID in byte. 0x14 AltBeacon 0x08 Eddystone EID 0x10 Eddystone UID 0x06 Eddystone UID, namespace matches configured one 0x01 Eddystone UID, namespace matches configured one, instance <= 255 (i.e. 1 byte) 0x02 Eddystone UID, namespace matches configured one, instance <= 65536 (i.e. 2 bytes)
1	signed, detected RSSI in dBm + 100 (i.e. -228 dBm to 27 dBm) encoded as -128 to 127
2 - 21	Beacon ID, variable length

Remarks

• Beacon data is encoded on a type-value basis, whereas the byte value of the type corresponds to the length of the ID-value
• The reporting stone (i.e. sender address) is included in the topic-name. It is part of the MQTT-header, hence.
• Using a 32-Bit timestamp is motivated by time_t having 32-Bit in ESP-IDF. Due to a year 2036-problem that may change in later versions of the protocol.

JSON status report

Topic: JellingStone/status/<MAC of BLE>

See content for details.

License

This file is part of JellingStone - (C) The Fieldtracks Project

JellingStone is distributed under the civilian open source license (COSLi).
Military usage is forbidden.

You should have received a copy of COSLi along with JellingStone.
If not, please contact info@fieldtracks.org

Misc notes

• 1100 Bytes for message Tcp-header: 20 Bytes (typically), IPv: 20 / 40 Bytes, MQTT: 14-Bytes + Topic, Websocket, + TLS, should be below a minimum MTU of 1280 => Hardly any need for fragmentation