STM32 F103RB: a 32-bit ARM Cortex M3 microprocessor
Clock Speed: 72 MHz
Operating Voltage: 3.3V
Input Voltage (recommended): 3.0V-12V
39 Digital I/O Pins (GPIO)
16 Analog Input Pins
12-bit ADC resolution (ADC)
15 PWM pins at 16-bit resolution (PWM)
Dedicated USB port for programming and communications (USB)
External JTAG interface (USB)
128 Flash and 20KB SRAM
64 Channel nested vector interrupt handler (including external interrupt on GPIO’s)
Integrated SPI (SPI)
Integrated I2C (I2C)
7 Channels of Direct Memory Access (DMA)
3 USART devices
Four 4-channel Timers (Timers)
Supplies up to 500mA @ 3.3v
Support for low power and sleep modes (<500uA)

serial flash

dpavlin@nuc:/nuc/stm32$ git clone https://github.com/jsnyder/stm32loader