The Blue Pill board offers much more than a replica Arduino for the same price. We show how to bring the circuit board to life.
Sometimes it can also be a little more: With the 32-bit wide ARM Cortex-M3 architecture of the STM32F103C8T6 and a clock frequency of 72 MHz, the very inexpensive one outperforms blue pillBoard an ATMega328P Arduino (16 MHz clock frequency) several times. The program memory, which is twice as large at 64 KB flash, and the comparatively lavish 20 KB RAM, allow for the fact that 32-bit programs require more storage space; the additional requirement is of course put into perspective if predominantly values with a width of 16 or 32 bits are to be processed, which an 8-bit always has to be broken down into several sub-steps.
The board also includes a real-time clock (RTC) clocked at 32,768 MHz with a separate crystal, but without a backup battery. In normal operation, the microcontroller uses 3.3V logic levels, but 5V input levels are also allowed on some pins. Otherwise, the board is refreshingly modest: The Chinese manufacturer has dispensed with lavish equipment with all kinds of peripheral components, such as the STM Discovery boards. You won’t even find a programming adapter or an interface component for the serial port.
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That doesn’t have to be a disadvantage: you don’t have to pay for components that are not required for the respective application; the board is available as a China import for well under three euros. Also, superfluous peripheral chips often block I/O pins, I2C or SPI interfaces that could be of good use externally.