General Overview

What is ZentriOS-WL?

ZentriOS-WL is a highly-optimized yet feature-packed IoT operating system designed specifically to power hardware platforms with secure Wi-Fi networking capability.

Hardware running ZentriOS provides a product with a powerful and secure wireless connection to a mobile device or the cloud.

You can build external MCU apps that communicate with ZentriOS using the extensive Wi-Fi Command API, via serial interface, HTTP REST or a remote terminal.

For the Bluetooth Low Energy version of ZentriOS, see ZentriOS-S.

Command API

The ZentriOS-WL Command API is available for applications connecting with a wired serial interface, or a wireless interface using HTTP REST or Remote Terminal. The API provides direct access to peripherals connected to ZentriOS hardware via GPIO. For a quick start guide to using a ZentriOS evaluation board, see Getting Started.

Features and Interfaces

The ZentriOS-WL Command API offers a powerful set of commands for control of connected devices, together with a large number of variables for configuration.

A host MCU communicates with ZentriOS via a UART.

A mobile or desktop app communicates with ZentriOS via the HTTP Server RESTful API or by the local or remote terminal interface.

The local or remote host sends commands to control the operation of ZentriOS and to exchange data with other devices on the network.

A summary of ZentriOS-WL features and interfaces is outlined in the following sections.

Wi-Fi, Networking & Web

Peripherals & Sensors


All ZentriOS commands can be issued manually using human mode or under host control using machine mode. Human mode should only be used for evaluation and manual testing. Machine mode is strongly recommended for production.

For human mode, the interfaces are a ZentriOS Terminal, the ZentriOS Web App, or a remote terminal.

Getting Started

To start using your ZentriOS hardware in human mode, see Getting Started.

ZentriOS Web App

The ZentriOS Web App provides complete monitoring and control of your ZentriOS hardware using a web browser.

See ZentriOS Web App.

Serial Interface

ZentriOS provides one of the easiest to use and most flexible serial Wi-Fi networking interfaces in the industry. The ZentriOS serial interface provides support for multiple serial buses, different serial communications modes including command mode and stream mode, and is easily configured for use by humans and machines alike.

See Serial Interface.


ZentriOS provides an easy-to-use serial API allowing you to focus your efforts on application development, rather than the time-consuming complexity and interoperability issues associated with the development of a full-featured secure wireless network stack.

Two Wi-Fi interfaces are supported, including a Wi-Fi client (wlan) and Wi-Fi soft access point (softAP) interface. WLAN and softAP cannot run concurrently.

See Wi-Fi Interface.

Networking and Security

ZentriOS includes a full IPv4 networking stack that supports a range of popular networking protocols including TCP, UDP, DNS, DHCP. Additional network application libraries are provided for native HTTP and cloud access.

See Networking and Security.


Various peripheral APIs are available to provide access to general purpose IOs (GPIOs), analog functions such as analog-digital and digital-analog converters, and timers including a real time clock. Special system and network functions can be assigned to GPIOs to enable handy features including:

See Peripherals.

File System

Most connected applications require the ability to store configuration information or cache local data. ZentriOS provides a reliable read/write filesystem and on-board flash storage to satisfy application storage requirements. With just a few simple commands, ZentriOS provides your application with complete access to local and network connected storage.

See File System.


For management of ZentriOS device memory, see Memory.

Configuration and Setup

Several options are available to setup a module running ZentriOS. The most common option, and also the most convenient when prototyping is to use a command line and serial interface such as a UART. A PC terminal can be quickly connected to a ZentriOS evaluation board, and within 60 seconds it is possible to be connected to a Wi-Fi network and downloading HTTP webpages or connecting to a remote TCP server.

Other methods for configuration, setup and Wi-Fi provisioning include:

See Configuration and Setup.

System Functions

System functions include:

See System Functions.

Update and Recovery

ZentriOS is part of a larger sophisticated application framework installed on all ZentriOS devices. The framework provides a hardened bootloader, read/write file system, safemode recovery mechanism, and over-the-air (OTA) update capability.

Zentri manages a secure on-line OTA server that offers each ZentriOS device with the ability to securely update individual files, applications or an entire firmware bundle. In the rare event that ZentriOS fails to regularly execute correctly, the bootloader switches the boot application to safe mode. The safe mode application provides the host with the ability to update the firmware, switch back to ZentriOS or even factory reset the module.

See Update and Recovery.