FST-01 with Heat Shrink Tube

Features of FST-01 with Heat Shrink Tube:

Components of FST-01:

• STM32F103TB: MCU is Cortex-M3 based ARM by STMicroelectronics.  It runs at 72MHz, it has 128KB flash ROM and 20KB RAM.
• SPI Flash memory: Secret data should be on MCU's flash, but non confidential data (such as backup of public keyring) can be on SPI flash memory. SST25VF032B (32Mbit = 4MB) is used. 
• USB Terminator: NUF2221W1 USB Upstream Terminator is used here. This is because it has the feature of electrostatic discharge protection.  It is also better for smaller footprint than two capacitors and two resistors.
• LDO Regulator: CAT6217-330 is used, for 3.3V Regulator (from 5V).  Currency of 150mA is enough.   
• XTAL 12MHz CL=18pF: 12MHz XTAL CL=18pF is used. This is because we can find smaller footprint XTAL for 12MHz (than 8MHz).
• LED: LED shows the status.
• SWD port: SWD port is to install firmware to MCU's flash ROM. 
• Extension port of VDD/GND/Port0/Port1: There are two I/O pins. (One I/O pin is not enough even for minimalist.) With two I/O pins, it can be:
  • TX and RX of serial communication
  • Drive and input of touch sensor
  • Controlling other MCU's SWD port
• USB plug A: It is used to connect the the FST-01 to USB port, like USB thumb drive.

Designer: Niibe Yutaka

Resources:

• FST-01 Wiki
• Gnuk
• NeuG 
• Product Page (STM32F103TB)
• Datasheet (STM32F103TB)