Walter Modem - LTE / GPS

Dom

Jun 11, 2025 • 2 min read

Walter is a board designed by DPTechnics which combines an ESP32-S3 and a Sequans Monarch 2 in a small form factor IoT module.

Setting Up Arduino IDE

Pretty easy to get the Walter plugged in and configured in Arduino IDE. It's also documented here.

Install the esp32 boards (by Expressif) and the WalterModem library.
Choose the right settings, I used the ESP32S3 board, and DPTechnics Walter is now an available board.

Writing Some Code

There are several examples available for Walter, of varying quality and states of development.

I chose the http_query example to start with to test LTE connectivity, but ended up using the Positioning example to base my final code on, and started by taking a copy of this example in my local IDE.

Once I hacked and slashed at these files a bit more, I came up with this code, which will test both the LTE and GPS connectivity

View the full code on GitHub Gist

Connectivity

Since the Walter requires (or at least works best with) a SIM card with LTE connectivity, I needed an IoT SIM card to get me started. I had a look at a couple options, and there are a few. I ended up choosing Hologram.io, as they have a nice control panel and have global coverage with a fair pricing structure for my use-case.

All Together

After building on the example code, I've connected to the LTE network, and obtained my own GPS co-ordinates! From here, I plan on starting to play with HTTP Sockets, and find a way to send push messages to my Walter.

Walter Modem Turn On :: v0.0.1
Walter's MAC is: CC:8D:XX:XX:XX:XX
Modem initialization OK
Modem identity:
 IMEI: 012345678910123
 IMEISV: 01234567891012
 SVN: 13
Modem radio technology: LTEM
SIM card identity:
 ICCID: 1234567890123456789123
 eUICCID: 

-----
1. Connect + Test Modem
-----
Connected to the network
Temp: 31.40°c
Connected on band 0 using operator Telstra Mobile (50501) and cell ID 12345.
Signal strength: RSRP: -103.60, RSRQ: -17.00.
rsrq: -170, rsrp: -103
rssi: -79 dB
epochTime: 1749363709, timeZoneOffset: 32
Disconnected from the network
-----
2. Get GPS Fix
-----
Disconnected from the network
Almanac data is available and should be updated within 15243760s
Real-time ephemeris data is available and should be updated within 5872s
Started GNSS fix

... after several re-tries ...

Started GNSS fix
...............
GNSS fix attempt finished:
  Confidence: 11.14
  Latitude: -33.856720
  Longitude: 151.215134
  Satcount: 12
  Good sats: 0
----- waiting 60s .....