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STM wifi module provides security for M2M and IoT

Steve Rogerson
March 9, 2017

The latest cloud-compatible wifi module from Geneva-based ST Microelectronics could accelerate development of all kinds of IoT and M2M devices. The module provides internet-security and application protocols, and includes a microcontroller capable of supporting operation in standalone or serial-to-wifi modes.
The SPWF04 module integrates an ARM Cortex-M4 STM32 microcontroller with multi-functional GPIOs and 2Mbyte on-chip flash and 256kbyte RAM for code and data storage. Features include a hardware cryptographic accelerator and an SPI port for faster host communications.
In addition, the MicroPython scripting engine simplifies development of custom applications to run directly on the module in standalone mode. Host interactions can use AT commands via a uart, compatible with the previous generation of wifi modules, or equivalent proprietary protocol over SPI.
Support for internet-security protocols includes WPA2-Enterprise, which enables authentication and access control in large networks, and WPS that helps safely connect devices such as printers or embedded systems. There is also support for HTTPS and encryption protocols including TLS, as well as secured over-the-air updates for applying software, firmware or flash file-system upgrades in the field via the wifi connection.
A TCP/IP protocol stack including HTTP, HTTPS, MQTT, SMTP and WebSockets simplifies connections to the cloud and mobile devices such as smartphones or tablets. Multiple UDP protocols, including TFTP, SNTP and mDNS, aid device discovery and file exchanges. Further highlights include IPv6 support, extended web-server functionality to simplify interaction with connected devices, and a Rest API that enables bandwidth-efficient interaction with web resources.
Versatile operating modes simplify integration with existing network infrastructure, using the module in station mode, or setting up direct point-to-point connections using the module in MiniAP mode as an access point for other devices, up to five stations. The module also comes with a socket layer capable of managing up to eight socket clients or two socket servers simultaneously handling up to eight clients each, or two WebSocket clients.
Like its predecessor, it benefits from high RF output power and receiver sensitivity, ensuring reliable communications even in harsh environments. Furthermore, the module delivers its performance and versatility within tight size and power constraints: it measures 26.92 by 15.24 by 2.35mm, and draws 40µA in standby and 5mA in idle connected mode.
It is available in two versions, with an efficient ISM-band antenna (SPWF04SA), or with a built-in U.FL connector for attaching an external antenna (SPWF04SC). Modules are FCC (USA), CE (EU) and IC Canada) certified, and RoHS compliant.