Walter is a small form-factor IoT system-on-module which combines the powerful ESP32-S3 processor with a 5G modem and GNSS receiver. On top of the ESP32-S3’s many built-in peripherals, such as UART, SPI, I2C, CAN, Wi-Fi b/g/n, and Bluetooth 5, Walter also boasts the second-generation Sequans GM02SP LTE-M/NB-IoT 5G modem and GNSS receiver.

The Walter module can be used for both prototyping and production, as it will be certified for FCC, CE, Australia SDoC, and New Zealand SDoC. We also guarantee a minimum of ten years availability, which makes it a uniquely reliable building block for your IoT application.

Walter comes with a range of 100% open source software libraries for jump-starting your 5G IoT project in minutes. So you can program in familiar languages and toolchains, Walter supports ESP-IDF, Arduino, Micropython, and Toit. No special dongles are needed to program Walter - just connect it directly to your development machine via a normal USB Type-C cable.

Antennas

Walter has a built-in Wi-Fi and Bluetooth antenna, and relies on external antennas for optimal LTE-M/NB-IoT and GNSS operation. There are two u.FL connectors especially for this purpose. We have chosen Taoglas as the recommended antenna partner because of their quality and ten-year availability guarantee. The antennas are designed to be stuck onto a product case. This self-adhesive flexible design makes it possible to easily integrate the antennas into your projects.

Carrier Board

Although it is possible to use Walter completely standalone, the system-on-module is designed to be incorporated into a product by plugging it into some kind of carrier board. We have designed a carrier board for Walter which allows you to build proof-of-concept IoT products in seconds. The name of this carrier board is Walter Feels. It contains everything you need to build a battery-powered IoT sensing platform:

• Wide input range (3.1 V - 35 V) MPPT power input
• Single- to multi-cell and multi-chemistry (LiFePo, Li-Ion, Lead) battery charger. The board starts with a battery voltage as low as 2.5 V.
• I2C battery and power management (Analog devices LTC4015)
• SD card slot
• Multiple sensors: temperature, humidity, barometric pressure, six DoF IMU, absolute CO2
• Multiple interfaces such as RS232, RS485, SDI-12, 1-Wire
• 3.3 V, 5 V and 12 V output
• Two GPIO pins directly from the Walter board
• Compatible with Takachi PFF13-4-13W housing for indoor applications

Use Cases

Walter has been created for remote sensing and control applications. In the past few months we have been working hard on perfecting our module by incorporating feedback from many beta testers, who have given us insights on possible use cases for Walter:

• GNSS tracker: As the GNSS receiver is built-in you don't even need an expansion board to build a global tracking solution with Walter. In fact, Walter comes pre-flashed with tracking firmware which uploads data to the walterdemo.quickspot.io demonstration platform.
• Remote weather station: When you plug Walter into its Walter Feels carrier board, you can monitor various sensors from virtually anywhere. The 5G connection (LTE-M or NB-IoT) has such good range that you can easily monitor remote locations. We even did a test where Walter was deployed on a measurement pole in the North Sea. Although normal 4G reception was very bad, the LTE-M connection worked flawlessly.
• Tank level sensor: To test the indoor coverage of Walter, we built a tank level sensor. We connected an ultrasonic sensor to Walter and tested the solution at various locations throughout Belgium. We were surprised with the results and even got a good signal two stories underground beneath a metal cover.

The above examples are only the tip of the iceberg, your creativity is the only limiting factor! Our team is already thinking about pet trackers, online delivery ticket printers, IoT access control systems, remote pump controls, and more.

Features & Specifications

• ESP32-S3-WROOM-1-N16R2 microcontroller:
  • Xtensa dual-core 32-bit LX7 CPU
  • 16 MiB quad SPI flash memory
  • 2 MiB quad SPI PSRAM
  • 150 Mbps 802.11 b/g/n Wi-Fi 4 with on-board PCB antenna
  • 2 Mbps Bluetooth 5 Low Energy with on-board PCB antenna
• Sequans GM02SP 5G modem:
  • Dual-mode LTE-M / NB-IoT (NB1, NB2)
  • 3GPP LTE release 14 (upgradeable up to release 17)
  • Ultra-low, deep-sleep mode in eDRX and PSM
  • Adaptive +23 dBm, +20 dBm and +14 dBm output power
  • Integrated LNA and SAW filter for GNSS reception
  • Assisted and non-assisted GNSS with GPS and Galileo constellations
  • Integrated SIM card
  • Nano SIM card slot
  • u.FL RF connectors for GNSS and 5G antennas
• Inputs & outputs:
  • 24 GPIO pins for application use
  • UART, SPI, I2C, CAN, I2S, and SD available on any of the GPIO pins
  • ADC, DAC, and PWM integrated in ESP32-S3
  • 3.3 V software-controllable output
  • USB Type-C connector for flashing and debugging
  • 22 test points for production programming and testing
  • On-board reset button
• Power supply
  • 5.0 V via USB Type-C
  • 3.0 - 5.5 V via Vin pin
  • Not allowed to use both power inputs simultaneously
  • Designed for extremely low quiescent current
• Form factor
  • Easy to integrate via 2.54 mm headers
  • 55 mm x 24.8 mm board dimensions
  • Pin- and footprint-compatible with EOL Pycom GPy
  • Breadboard friendly
• Software
  • Libraries for the Espressif IDF
  • Libraries for the Arduino ecosystem
  • Libraries for the Micropython
  • Future support and libraries for Toit
  • Natively supported in the BlueCherry.io IoT platform
  • We are open to other suggestions
• Certifications
  • Industrial temperature range of -40°C to +85°C
  • Pending certification for CE, FCC, Australia and New Zealand
  • Designed and manufactured in the European Union
  • Ten-year availability guarantee
  • CE (EU), FCC (US), SDoC (AU), SDoC (NZ)

Pinout Diagram

Open Source

We are continuously improving the documentation of Walter and its accessories. We also actively encourage everyone to contribute to this effort. Currently the following resources are available:

• Schematics
• Datasheet
• Footprints and renders
• Libraries
• Documentation
• Walter Feels KiCad project

First Production Run

Walter is ready for production and conformity testing. In the past few months we have been working closely with the production house to get the design for manufacturing (DFM) just right. Below is a video showing the complete manufacturing process.