Walter

Overview

Walter is a compact IoT development board that combines an Espressif ESP32-S3 SoC with a Sequans Monarch 2 GM02SP LTE-M/NB-IoT/GNSS modem. More information about Walter can be found on the QuickSpot Website [1] and on the QuickSpot GitHub page [2].

Hardware

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 Monarch 2 GM02SP modem:

  • Dual-mode LTE-M / NB-IoT (NB1, NB2)

  • 3GPP LTE release 14 (Upgradable 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

Supported Features

Current Zephyr’s Walter board supports the following features:

Interface

Controller

Driver/Component

UART

on-chip

serial port

GPIO

on-chip

gpio

PINMUX

on-chip

pinmux

USB-JTAG

on-chip

hardware interface

SPI Master

on-chip

spi

TWAI/CAN

on-chip

can

ADC

on-chip

adc

Timers

on-chip

counter

Watchdog

on-chip

watchdog

TRNG

on-chip

entropy

LEDC

on-chip

pwm

MCPWM

on-chip

pwm

PCNT

on-chip

qdec

GDMA

on-chip

dma

USB-CDC

on-chip

serial

Wi-Fi

on-chip

Bluetooth

on-chip

Cellular

on-board

modem_cellular

Prerequisites

Espressif HAL requires WiFi and Bluetooth binary blobs in order work. Run the command below to retrieve those files.

west blobs fetch hal_espressif

Note

It is recommended running the command above after west update.

Building & Flashing

Simple boot

The board could be loaded using the single binary image, without 2nd stage bootloader. It is the default option when building the application without additional configuration.

Note

Simple boot does not provide any security features nor OTA updates.

MCUboot bootloader

User may choose to use MCUboot bootloader instead. In that case the bootloader must be build (and flash) at least once.

There are two options to be used when building an application:

  1. Sysbuild

  2. Manual build

Note

User can select the MCUboot bootloader by adding the following line to the board default configuration file.

CONFIG_BOOTLOADER_MCUBOOT=y

Sysbuild

The sysbuild makes possible to build and flash all necessary images needed to bootstrap the board with the ESP32-S3 SoC.

To build the sample application using sysbuild use the command:

west build -b walter/esp32s3/procpu --sysbuild samples/hello_world

By default, the ESP32 sysbuild creates bootloader (MCUboot) and application images. But it can be configured to create other kind of images.

Build directory structure created by sysbuild is different from traditional Zephyr build. Output is structured by the domain subdirectories:

build/
├── hello_world
│   └── zephyr
│       ├── zephyr.elf
│       └── zephyr.bin
├── mcuboot
│    └── zephyr
│       ├── zephyr.elf
│       └── zephyr.bin
└── domains.yaml

Note

With --sysbuild option the bootloader will be re-build and re-flash every time the pristine build is used.

For more information about the system build please read the Sysbuild (System build) documentation.

Manual build

During the development cycle, it is intended to build & flash as quickly possible. For that reason, images can be build one at a time using traditional build.

The instructions following are relevant for both manual build and sysbuild. The only difference is the structure of the build directory.

Note

Remember that bootloader (MCUboot) needs to be flash at least once.

Build and flash applications as usual (see Building an Application and Run an Application for more details).

# From the root of the zephyr repository
west build -b walter/esp32s3/procpu samples/hello_world

The usual flash target will work with the walter board configuration. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b walter/esp32s3/procpu samples/hello_world
west flash

Open the serial monitor using the following command:

west espressif monitor

After the board has automatically reset and booted, you should see the following message in the monitor:

***** Booting Zephyr OS vx.x.x-xxx-gxxxxxxxxxxxx *****
Hello World! walter/esp32s3/procpu

Debugging

ESP32-S3 support on OpenOCD is available at OpenOCD ESP32 [4].

ESP32-S3 has a built-in JTAG circuitry and can be debugged without any additional chip. Only an USB cable connected to the D+/D- pins is necessary.

Further documentation can be obtained from the SoC vendor in JTAG debugging for ESP32-S3 [3].

Here is an example for building the Hello World application.

# From the root of the zephyr repository
west build -b walter/esp32s3/procpu samples/hello_world
west flash

You can debug an application in the usual way. Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b walter/esp32s3/procpu samples/hello_world
west debug

References