Microcontroller Boards


A certified ESP32-S3 module with LTE-M, NB-IoT, and GNSS for prototyping and production

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Walter is a small-form-factor IoT system-on-module (SoM) that combines a powerful ESP32-S3 system-on-chip (SoC) with a second-generation Sequans GM02SP LTE-M/NB-IoT 5G modem and GNSS receiver. Its ESP32-S3 provides many built-in peripherals as well, including UART, SPI, I²C, CAN, Wi-Fi b/g/n, and Bluetooth 5. Walter is the only module that packs all of these connectivity options into such a small package.

Walter functionality
1. 5G Modem & GNSS receiver6. Integrated GNSS LNA + SAW11. 2.54 mm pin headers
2. Reset button7. 3.3 V out software switch12. Test pads
3. USB Type-C8. Ultra low sleep current DC-DC13. Nano SIM slot
4. 5G antenna connector9. ESP32-S3 SoC
5. GNSS antenna connector10. Wi-Fi & BLE antenna

Open Hardware Powered by Open-Source Software

To help you get the most out of Walter, we have published the schematic and the KiCAD footprint, both of which are available on GitHub, along with our datasheet, which describes all pins and test pads so you don’t have to go hunting for them.

Walter comes with a range of fully open-source software libraries so you can jumpstart your 5G IoT project in minutes using your preferred languages and toolchains. It supports ESP-IDF, Arduino, MicroPython, and Toit. No special dongles are needed to program Walter – just connect it directly to your dev machine using a regular USB Type-C cable.

Our embedded-software team is continuously improving Walter’s open-source libraries, which you can find in our GitHub repo. These libraries are optimized for flexibility and ease-of-use, with a particular emphasis on:

More Than a Development Board

Evolving a prototype into a commercial offering is the most daunting stage of product development. Walter aims to reduce this complexity, especially for low- to medium-volume production. It is the perfect entry point for businesses looking to develop their own 5G connected IoT products.

How did we approach the challenge of designing a board like this? First of all, you will find no unnecessary components on Walter. There are no sensors, no RGB LEDs, and no charging circuits, to name just a few intentional omissions. Each of these "features" would have increased Walter’s cost while sitting unused most of the time for most applications. Instead, you will find a number of test pads, on the bottom of the board, which can be used to automate firmware flashing and product testing.

Secondly, we have certified Walter for FCC, CE, UKCA, IC, and RCM (for Australia and New-Zealand). Unless you add another radio to your Walter-based product, your certification costs and risks will be minimal.

Next, our team has years of experience in embedded development, so we know that most dev boards are only available for a few years, which can be a problem because IoT products are often deployed in the field for much longer than that. Reliable, long-term support is essential for IoT products, so we have negotiated contracts with our component suppliers that allow us to guarantee availability for a minimum of ten years.

Walter's size in comparison with an AA battery
Walter's size in comparison with an AA battery

Finally, did we mention how small we made it? Walter is only 24.8 x 55 mm, so it will fit in just about any product. In fact, we’re not aware of any possible way to make a smaller standalone board with support for these RF technologies.

Ultra Low-Power Deep Sleep

For many battery-powered applications, Walter will spend most of its time in deep sleep. It is therefore critical that we consume as little power as possible in this mode, which was among our key requirements during the design stage. We are extremely proud of the result and have validated that Walter only consumes 9.8 µA in deep sleep mode:

As a result, Walter can sleep for over 34 years on a single 18650 cell with an average capacity of 3000 mAh.

Compatible With the Former PyCom GPy

There are many products on the market that are based on the PyCom GPy, which is EoL and no longer available. Walter is fully pin compatible with the GPy and can be swapped in without redesigning carrier boards. PyCom’s closed-source solution suffered from various hardware shortcomings, as well. We have addressed all of those issues, making Walter not just a replacement, but a serious upgrade. Have a look at this wonderful feedback we received from one of our beta testers:

We have converted our GPy application over to Walter with good results. Key points include:

Thanks for the great work!

Tommy Lanier,
Computer Engineered Solutions, Inc.

Pre-Certified Antennas

Walter has a built-in Wi-Fi and Bluetooth antenna but relies on external antennas for optimal LTE-M/NB-IoT and GNSS operation. It includes two u.FL connectors for this purpose. We have chosen Taoglas as our recommended antenna partner because of their quality and their ten-year availability guarantee. The antennas in our devkit are adhesive, which makes them easy to integrate into your products by attaching them to an enclosure.

Walter with antennas
Walter with antennas

The Walter Feels Carrier Board

Although it is possible to use Walter as a standalone module, it was designed to be incorporated into your product by way of a carrier board. We provide just such a carrier board to help you design and build proof-of-concept IoT products as quickly as possible. We named our carrier board Walter Feels, and it contains everything you need to build a battery-powered IoT sensing platform:

Walter Feels with and without Walter and antennas

We have created a sample Arduino sketch that you can run on Walter Feels. It sends data to the Walter Demo platform, which immediately visualizes all incoming sensor and power-management data.


We created Walter for remote sensing and control applications, and we’ve been working hard to perfect it by incorporating feedback from beta testers who’ve given us insights related to various other possible applications, including:

Applications for Walter and Walter feels
Applications for Walter and Walter feels

The examples above are only the tip of the iceberg. Our team is already thinking about pet trackers, ticket printers for online-delivery services, IoT access-control systems, and remote pump controls, among other possible applications. And we can’t wait to hear your ideas as well!

Features & Specifications

Pinout Diagram

Walter pinout diagram


WalterPycom GPyAVR IoT miniArduino MKR NB 1500iLabs RP2040 connectivityParticle BRN404X
CPUESP32-S3 (Dual 240 MHz) ESP32 (Dual 240 MHz) AVR128DB48 (24 MHz) SAMD21 (48 MHz) RP2040 (Dual 133 MHz) nRF52840 (64 MHz)
NB-IoTYes Yes Yes Yes Yes Yes
LTE-MYes Yes Yes Yes Yes Yes
2G GPRSNo No No No Yes No
3GPP release14 13 14 13 13 14
GNSSYes No No No No No
WiFiYes Yes No No Yes No
BLEYes Yes No No Yes Yes
Size (mm)24.8 x 55 20 x 55 23.78 x 81.69 25 x 67.6 42 x 54 22.86 x 50.8
Battery chargerNo No Yes Yes Yes Yes
USB connectorUSB Type-C None USB Type-C Micro-USB USB Type-C Micro-USB
Open SourceHW + SW No HW + SW HW + SW HW + SW HW + SW
RAM KiB2,576 4,608 16 32 264 256
Flash (KiB)16,384 8,192 128 256 8,192 1,024
SoftwareESP-IDF, Arduino, MicroPython, Toit MicroPython C Arduino Arduino Device OS
Deep sleep (uA)9.8 17 70 500 260 106
AvailableYes No Yes Yes Yes Yes

Support & Documentation

We are continuously improving our documentation and design documents for Walter and its accessories. We invite you to have a look at (and contribute to!) the following resources:

Based on feedback from our beta testers, we will launch a documentation website to make some of the information above more accessible and to host sample code for various applications that you can use to get started with your own projects. Our team is actively monitoring GitHub issues and email correspondence, so if you’d like help implementing your project, let us know, and we may be able to offer contracting support as well.

Manufacturing Plan

The Walter team has over seven years of experience in hardware and software development for the Internet of Things. Over the past few months, we’ve been working with our Belgian manufacturing partner to perfect our design and prepare for mass production. Walter will be manufactured in a state-of-the-art European factory, as demonstrated in the video below:

Fulfillment & Logistics

After our production run is complete, we will package everything up and send it along to Crowd Supply’s fulfillment partner, Mouser Electronics, who will handle distribution to backers worldwide. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.

Risks & Challenges

We have worked on Walter for about a year. During that time, it’s gone through a total of six different iterations, each of which was tested not only by our own team but by a network of beta testers all over the world. You can see the results in realtime on our demo platform. We are quite certain that Walter is stable, even when operating in difficult environments, and we believe that our biggest risks have already been taken.

We are currently finalizing our certification process, which has involved two stages:

Walter undergoing certification testing
Walter undergoing certification testing

We expect to complete the above certification process any day now. While there is always a chance that we could fail one of the formal compliance tests, doing so would just lead us to mitigate the issue by implementing relatively minor design changes. We would anticipate no more than a one- to three-month delay should this occur.

In the Press

Circuit Digest

"A cutting-edge, certified ESP32-S3 module with LTE-M, NB-IoT, and GNSS capabilities, set to revolutionize IoT (Internet of Things) prototyping and production."


"Walter is an ESP32-S3-based IoT system-on-module supporting LTE-M/NB-IoT 5G and GNSS. This compact device is certified for FCC, CE, Australia SDoC, and New Zealand SDoC, so this module can be used for prototyping and production."

Andreas Spiess

"The Walter library and sketches use the optimized UDP and CoAP protocols for communication. DPTechnics started a new open-source library that is up to the task, and maybe it will become the new standard for modern cellular protocols."

Hackster News

"Compact Walter SoM scales from prototype to mid-volume production. It contains wireless connectivity, 10-year availability, and 24 GPIOs."

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Produced by DPTechnics in Knokke-Heist, Belgium.

Sold and shipped by Crowd Supply.

Walter SoM

Walter is a small-form-factor IoT system-on-module (SoM) that combines a powerful ESP32-S3 SoC with a 5G modem and a GNSS receiver. It supports Wi-Fi, Bluetooth, LTE-M, NB-IoT, and GNSS connectivity.

$77 $8 US Shipping / $18 Worldwide

Walter Devkit

Everything you need to get Walter online in a matter of minutes, including antennas, a 250 MiB worldwide Soracom SIM card, a USB Type-A to Type-C cable, and a USB Type-C to Type-C cable. Our devkit also comes with 30 minutes of expert support to help you kickstart your project. (You'll be able to book a video meeting with one of our engineers by providing the IMEI and MAC addresses of your modem.) Walter is a small-form-factor IoT system-on-module (SoM) that combines a powerful ESP32-S3 SoC with a 5G modem and a GNSS receiver. It supports Wi-Fi, Bluetooth, LTE-M, NB-IoT, and GNSS connectivity.

$310 $8 US Shipping / $18 Worldwide

Walter Feels

Walter Feels is a carrier board for the Walter module. It provides an MPPT battery charger, battery management with coulomb counter, and various sensors, including temperature, humidity, barometric pressure, and 6-DoF IMU. Walter Feels supports interfaces like RS232, RS485, SDI-12, CAN bus, and GPIO with ADC functionality. It includes a MicroSD card slot and provides power output at 3.3, 5, and 12 V. It also hosts a connector for the Sensirion SCD30 absolute CO₂ sensor (not included).

$104 $8 US Shipping / $18 Worldwide

About the Team


Knokke-Heist, Belgium  ·   dptechnics  ·   dptechnics  ·   dptechnics.com

We develop and produce next-generation, internet-connected products, from embedded systems to software to industrial design. QuickSpot is our line of IoT building blocks designed to help you focus on your product rather than on low-level technical details.

Ronny Pape
Dries Vandenbussche

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