====== Most Noticeable Platforms ======
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The IoT market is an emerging one. New hardware solutions appear almost daily, while others disappear quickly. At the moment of writing the first version of this book (2016-2019), some hardware solutions that seemed prominent for at least a couple of years existed. After a few years, while the 2nd edition of the publication is being prepared (2023–2025), most of the hardware solutions described previously are still present on the market, even strengthening their position and having modernized and improved versions (e.g. ESP32 as the successor of ESP8266). However, some other platforms increased their popularity, mainly because of their appearance in the VSCode programming environment with PlatformIO, and what is even more important, the possibility of writing programs in the Arduino model. In the following sections, a short review of these platforms is provided.
  * AVR: Arduino – a development board using the Atmel microcontroller, undoubtedly the most popular development platform for enthusiasts and professionals. Arduino itself barely offers networking capabilities yet; there are many extension boards, including wired and wireless network interfaces.
  * ESP: Espressif (Espressif Systems) – the great SoC solutions with wireless network interfaces built-in; the family of Espressif chips includes ESP8266 (WiFi) and ESP32 (802.11: WiFi, Bluetooth and 802.15.4: Matter, BLE, Thread and Zigbee).
  * nRF52: Nordic Semiconductor SoC based on ARM architecture offers 802.15.4 protocols: Bluetooth, ZigBee, Matter, and Thread.
  * STM32: Another ARM-based family of SoCs; some have Bluetooth wireless module built-in and 802.15.4 protocols.
  * ARM: Raspberry Pi (and its clones) – advanced boards, including Linux operating system with GUI interface, even able to replace desktop computers. There are also, however, low-powered, constrained devices with ARM cores, such as Cortex-M0+ (Raspberry Pi Pico/Pico W: RP2040).

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The following chapters are dedicated to the families of the devices, describing their main features:
  * [[en:iot-open:hardware2:arduino|Arduino]],
  * [[en:iot-open:hardware2:espressif|Espressif family]],
  * [[en:iot-open:hardware2:nrf52|nRF52]],
  * [[en:iot-open:hardware2:stm32|STM]],
  * [[en:iot-open:hardware2:RaspberryPI|Raspberry PI]].
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