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Arm's Cortex-M0 is at the low end of the 32-bit spectrum. It is designed to compete with 8- and 16-bit micrcontrollers while providing the power and flexibility of the Cortex architecture. STMicroelectronics adds to its Cortex portfolio with the STM F0 that is priced around $1. The STM32 F0 Series (Fig. 1) runs at 48 MHz. It has up to 128 Kbytes flash and 20 Kbytes SRAM. Some chips have RAM parity support. The F0 also has DMA-support CRC integrity check of flash memory. These are required for Class B-ready, safety-related applications. There are two watchdog timers as well. Memory and peripherals are linked via a bus matrix that allows the 5-channel DMA to operate in parallel with the processor.
ig. 1: STM32 F0 includes support for HDMI Consumer Electronics Control (CEC).
The Cortex-M0 is at the low end of the power and performance spectrum but the STM32 F0 performs very well. It's CoreMark result is over 1.6 CoreMarks/MHz besting may 8- and 16-bit processors. It is designed to be very power efficient drawing only 5μA in stop mode and 2μA in standby mode. It also has a very fast wake up time. HDMI Consumer Electronics Control (CEC) is part of the HDMI specification. CEC allows an HDMI connection to control up to 10 CEC devices. The STM32 F0 can be one of those CEC devices. STMicroelectronics includes a software library that supports CEC. The analog peripheral set is similar to that found on other STMicroelectronics microcontrollers. The STM32 F0 has 12-bit, 1 Msample/s ADC as well as a 12-bit DAC and a pair of comparators. The analog subsystem has a separate power supply. Capacitive touch support can handle 18 keys as well as sliders and wheels. The digital peripheral set includes serial ports with IrDA support. There is an infrared software library to simplify development chores. The I2C interface runs at speeds up to 1 Mbit/s. SPI is also supported. The 32-bit timers work with up to 17 capture-compare pins. They have PWM support but there is also a motor control subsystem designed to handle permanant magnet synchronous motors (PMSM). STMicroelectronics provides a motor control library. The real time clock (RTC) supports sub-second alarms with a 31μs step designed for RF applications. The calendar used a BCD format. It has configurable windows/step calibration trimming support. Development can start using a number of eval boards. The STM320518 evaluation kit (Fig. 2) is priced at $199. The board includes a QVGA LCD display. Developers have access to a graphics libraries that work with the display.
Fig. 2: The STM320518 includes a QVGA display.
The $7.99 STM32F0Discovery (Fig. 3) follows STMicroelectronics Discovery line. This DIP module has a USB debug interface and exposes most of the chip's peripheral pins.
Fig. 3: STM32F0Discovery is a low cost eval platform.
The STM32 F0 requires a 1.8V to 3.6V power supply. Battery backup support in standby mode includes 20 bytes of backup registers. Standby mode uses only 0.43 μA including RTC support. It is available in a range of chip packages that can handle temperature extremes.
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