Conexio Stratus - An nRF9160 board with solar energy harvesting capability (Crowdfunding)

Conexio Stratus board is equipped with Nordic Semi nRF9160 System in Package (SiP) with LTE-M (eMTC) & NB-IoT cellular IoT connectivity as well as GPS support through a pair of u.FL connectors for antennas, together with 500MB of mobile data valid for ten years.

Designed for battery operation, the devkit comes with built-in battery charging, monitoring, and energy-harvesting circuitry, plus an accelerometer and a temperature and humidity sensor that makes it ideal for prototyping cellular IoT systems such as asset-tracking applications, environmental monitoring, and smart-meter monitoring, among others.

Conexio Stratus board

Conexio Stratus specifications:

SiP – Nordic Semi nRF9160 system-in-package with Arm Cortex M33 MCU, 1 MB Flash, 256 kB RAM, cellular IoT modem, and GPS.
Cellular Connectivity
- 3GPP LTE release 13 Category M1 and NB1 compliant
- 3GPP release 14 NB2 compliant
- RF Transceiver for global coverage supporting bands:
  - Cat-M1: B1, B2, B3, B4, B5, B8, B12, B13, B14, B17, B18, B19, B20, B25, B26, B28, B66
  - Cat-NB1/NB2: B1, B2, B3, B4, B5, B8, B12, B13, B17, B18, B20, B25, B26, B28, B66
- Supports 4FF Nano SIM
- 1x u.FL antenna connector
GNSS – GPS receiver (GPS L1 C/A supported), 1x u.FL connector for active antenna
Sensors
- Sensirion SHT4x temperature and humidity sensor
- ST Microelectronics LIS2DH MEMS motion sensor (3-axis Femto accelerometer)
USB – 1x Micro USB port for USB-to-Serial, DFU, application firmware programming and debugging, and LiPo battery charging
Expansion – 32 through holes (2.54mm pitch) with 26 user-programmable GPIOs
Debugger & Programmer – J-Link and CMSIS-DAP based programmers via 10-pin (1.27 mm pitch) pin connector
Misc – Reset and user push buttons; ON/OFF slide switch; 1x user LED (green)
Power Management
- Energy harvester IC – E-peas Semiconductors AEM10941 solar energy harvester
  - Vin: 50 mV to 5 V
  - Cold start: 3 μW @ 380 mV
  - Power input: 3 μW to 550 mW
  - Maximum power point tracking (MPPT) support
  - Supports Li-ion and NiMH battery types
  - Max solar panels: up to 7 solar cells simultaneously
- Power Supply
  - 3.3 V Buck/Boost up to 0.9 A of current draw
  - Operating range 2.8 to 5.5 V
  - 2-pin JST connector for LiPo battery
  - Charge rate set to 300 mA with yellow LED indication
  - Maximum output current: 800 mA
  - Current consumption in low-power-mode: < 5 μA
Dimensions – 50.8 x 22.86 mm
Weight – ~5 grams.

Software integration

The hardware itself is interesting, but we’ll already seen other similar nRF9160 boards with the likes of nRF9160 Feather, Icarus IoT, or Pebble Tracker, although AFAICR, Stratus is the first with an energy harvesting chip. But it seems Conexio puts a lot of effort into making sure the platform is easy to use from the start.

First, the board comes preloaded with 500 MB of mobile data and a total of 250 SMS messages, valid for 10 years with service in more than 100 countries worldwide. 1NCE has a similar 10-year plan with 500MB of data, so it could be in collaboration with them, or another company, I could not find the details. The result is the same in that you can use mobile data for free for up to ten years as long as you don’t exceed the quota.

Conexio Stratus is preprogrammed with MCUBoot bootloader, and the board is compatible with various cloud platforms including Edge Impulse and Golioth to provide machine learning (e.g. for predictive maintenance) and seamless Over-the-Air (OTA), as well as Datacake IoT platform that does not require any programming knowledge. This should make it easy to develop applications in the fields of environmental monitoring, smart agriculture, smart energy and utilities (think Smart Grid), healthcare (e.g. patient monitoring) and real-time asset tracking

Development tools

Conexio provides both hardware and software development tools for the Stratus board starting with a shield equipped with standard MikroBus, Qwiic, and Grove connectors to easily extend functionality from a choice of over a thousand modules.

The shield also includes a 2-pin JST connector for solar-panel input as well as a user-programmable LED for debugging.

Nordic Semi already offers the Zephyr based nRF Connect SDK for nRF91 and nRF52 WiSoCs, but Conexio still developed the Conexio Studio IDE to create and debug Conexio Stratus and Zephyr RTOS projects in Visual Studio Code. The tool integrates built-in templates to easily get started, and examples and the VSCode extension will be available for download when the campaign begins.

The board is also compatible with Memfault to debug, monitor devices, and resolve any issues with cloud connectivity.

You can see a comparison between Stratus and other nRF9160 boards below that highlights the hardware and software benefits of the board.

The company claims the hardware will be open-source with both software and hardware design files released on Github. Right now the source files for the board are not available yet, but those should be made available before the board ships.

Conexio has just launched the Stratus board and shield on Crowd Supply with a $10,000 funding goal. Rewards start at $139 for the Stratus board with 10-year connectivity, while the shield adds $19, and an accessory bundle with antennas, micro USB and SWD cables add another $39. Shipping is free to the US and $12 to the rest of the world, and backers should start getting their rewards shipped in May 2022.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.