ARM for Advanced Risc Machines: the Commonest 32-bit Architecture

STM32

The STM32 is a family of 32-bit microcontrollers from STMicroelectronics and is based on the ARM Cortex-M CPU. While there are multiple versions of the STM32, the most common version is the "Blue Pill", featuring a 72 MHz ARM Cortex M-3 CPU.

The Blue Pill has 64 KB of Flash and 20 KB of SRAM memory, along with 32 digital I/O pins, 12 of which support Pulse Width Modulation. The Blue Pill also has 14 analog input pins, three Serial UART ports, two SPI buses and two I2C buses. The Blue Pill version is available from online suppliers such as AliExpress usually for under $3.00.

Comparison between RaspBerry Pi, Beaglebone Black, SMT32 Boards...

In the field of single-board computers, two names stand out: Raspberry Pi and Beagle Bone Black. They are quite popular because they are powerful pieces, in a very small and pretty inexpensive package, ideal for every hobbyist, developer, or teacher. Though most features of them are common, one still exists to differentiate each uniquely in a manner suitable for a different type of project... (see https://www.geeksforgeeks.org/linux-unix/difference-between-raspberry-pi-and-beaglebone-black/)

The Raspberry Pi excels in general computing, multimedia, and ease of use with a vast community, better built-in connectivity (Wi-Fi/BT), and powerful specs (newer models), ideal for beginners, servers, or media centers. The BeagleBone Black (BBB) shines in industrial control, robotics, and real-time projects due to its more extensive, adaptable I/O (GPIO, analog), integrated microcontrollers (PRUs), and durable design, suiting hardware-focused, mission-critical applications despite its older tech and smaller community.

(From AI OverView, by Google)