Electronics
The WII6 board carries an STM32U575 on Zephyr, an ESP32-S3 debug processor and an Iridium Certus modem, with switched and monitored power and a firmware update that reverts itself.
The WII6 buoy
A WII6 buoy measures surface motion on sea ice or in open water, computes the wave statistics on board, sends the selected data over Iridium and keeps the full record on the card.
Inside a WII5 buoy: the main board, Iridium modem and motion sensor in a Pelican case. WII6 is designed to fit the same enclosures.
A WII6 buoy sits on sea ice or floats at the ice edge and measures how the surface moves. It records motion, computes the wave statistics on board, and sends the selected data over Iridium. The full record is written to the card.
Built to your specification
Each buoy is built for its deployment. The figures on this site are examples; these are the choices you make:
| Choice | Examples |
|---|---|
| Motion sensor | a single-axis Kistler accelerometer, a Sparton AHRS-M2, or the sensor your analysis needs |
| Sampling rate | 8 Hz and 64 Hz are typical |
| Capture length | fifteen minutes is typical; shorter or longer to suit the site |
| Reporting interval | from every few minutes to once a month |
| Heading | from the motion sensor, or dual-antenna GNSS for accurate heading near the poles |
| Temperature | a probe arrangement to suit the deployment |
| Enclosure | an ice-surface box, a floating hull, or your own platform |
What it measures
| Sensor | Measurements and purpose |
|---|---|
| Motion sensor | acceleration and orientation for the wave maths |
| GNSS | position and time from a single receiver |
| Heading | from the motion sensor or a dual-antenna GNSS receiver |
| Temperature probes | air and water temperature, according to the deployment’s probe arrangement |
| Power monitoring | power and voltage measured on multiple buses to track the buoy’s health |
What it sends
The smallest message is 326 bytes of wave results: significant wave height, peak period, the power spectrum, direction and quality flags. Position and buoy health can be sent alongside them.
You choose which captures send just the power spectrum, which send a 2 Hz record, and which send the full-rate record. For example, for a fifteen-minute capture the 2 Hz record is about 56 kB and fits in a single Iridium Certus message. It lets you rerun the later processing stages on shore with different settings.
Full-rate transfers use more airtime and cost more, so the 2 Hz record is the practical choice for most satellite reprocessing requests. The full record remains on the card for recovery. Every record, the full record included, carries the filtering the motion sensor applies internally.
What changed from WII5
| Feature | WII5 v2 | WII6 |
|---|---|---|
| Main processor | ATmega2560 at 11 MHz, 8 kB RAM | STM32U575, Cortex-M33 at 160 MHz, 786 kB SRAM |
| Wave maths | on a Raspberry Pi woken for the job | on the main processor, using SRAM |
| Satellite | Iridium SBD, 340 bytes a message | RockBLOCK 9704, Iridium Certus, about 100 kB a message |
| Firmware | Arduino | Zephyr RTOS |
| Debug and local access | Raspberry Pi | ESP32-S3 with WiFi, off in deployment |
| Storage | two SD cards | one SD card, a write-once record layout |
| Power | per-peripheral switches | switched supplies, with power and voltage measured on multiple buses |
Earlier generations used a Kistler single-axis accelerometer with a lower-cost inertial measurement unit (IMU); WII5 used a Sparton motion sensor. Either can be fitted to WII6. The heritage page traces that development.
Where it stands
The WII6 electronics are on the bench on development boards. The Sparton streams into the maths on the STM32, captures go to the card, bench buoys post to the WII6 cloud and take commands back, and the sleep and the firmware update have been exercised. A bench buoy has run its cycle unattended for a week: an hourly capture, its result posted to the cloud, and the main processor asleep in between. Revision A of the main board is drawn and routed. The news has the detail. If you are planning a season, get in touch for the current development schedule.
- Electronics: the board, power monitoring and firmware.
- Hulls and boxes: what the enclosure has to survive and the forms it takes.
- Uses: where a buoy can go, and what it can be fitted to.
Hulls and boxes
What a WII buoy enclosure has to survive on sea ice and in open water, and the forms it takes: the ice-surface box, the floating hull, the tethered variant.