News: I have restructured the options page, introducing a bunch of new chips and manufacturers into the mix. Read below for a full list of specifications.

So your project happened to outgrow Arduino Zero or Uno, but stepping up to Due or Mega seemed too much? This board can be a solution to that.

What's New

• This board deprecates the previous design, which suffered from an improperly designed USB circuitry and a suboptimal automatic power input switch-over scheme.
• This board is also tested with a lot more chips, including ones with a different processor architecture (STM32F072C8T6 and STM32F303CCT6, which is based on ARM Cortex-M0 and Cortex-M4F respectively) and other manufacturers (GigaDevices GD32F103CBT6.)
• The onboard USB to UART chip is updated to WCH CH340B. The original CH340G driver should still work, but thanks to the serial number written into the devices you should now have a device node name that sticks.

Specification

3.3V, ARM architecture, Cortex-M (speed and instruction set depend on the processor selection) in LQFP-48 package

• Microcontroller options:
  • STM32F072C8T6: Cortex-M0 @48MHz, 64kB Flash, 16kB SRAM
  • STM32F103CBT6: Cortex-M3 @72MHz, 128kB Flash, 20kB SRAM
  • STM32L151CCT6: Cortex-M3 @32MHz, 256kB Flash, 32kB SRAM, ULP
  • STM32F303CCT6: Cortex-M4F @72MHz, 256kB Flash, 40kB SRAM
  • STM32L433CCT6: Cortex-M4F @80MHz, 256kB Flash, 64kB SRAM
  • GD32F103CBT6: Cortex-M3 @108MHz, 128kB Flash, 20kB SRAM
  • BLM32F103CBT6: Cortex-M3 @96MHz, 128kB Flash, 20kB SRAM
  • AT32F403CGT6: Cortex-M4F @200MHz, 1MB Flash, 224kB SRAM
• Onboard 8MHz high-speed crystal for main PLL and 32768Hz watch crystal for RTC
• Two USB 2.0 Full-Speed interfaces: one native to the processor, one for on-board USB to Serial adapter
• CR1220 Backup battery for real-time clock
• Switch-mode power architecture for ultra low power operation

This board comes in the same physical dimensions as Arduino Uno and follows the Arduino 1.0 pinout, and existing shields should fit.

Software

The "official" software for this board is not yet ready for release.

The generous buyer Shinichi have provided a port of STM32duino and bootloader for this board. Please check out her work:

• Bootloader: https://github.com/hanyazou/STM32duino-bootloader/tree/SushiBitsOneF103C
• Arduino Core: https://github.com/hanyazou/Arduino_STM32/tree/SushiBitsOneF103C
• Demonstration: https://www.youtube.com/watch?v=b_IgPVzI7hU

The SushiBits Family

SushiBits is a family of Arduino-compatible development boards. The family includes:

• SushiBits One: the original SushiBits ARM Development Kit, for various chips that follow the same pinout as STM32F103CBT6. This is the page for SushiBits One.
• SushiBits Pro: based on SushiBits One, but comes with an on-board DAP42 CMSIS-DAP debugger.
• SushiBits ARM Classic: the SushiBits for people that prefers time-honored technology, uses an ARM7TDMI-S chip.

More variants will be introduced down the road.

Story of Creation

This design is one of my post-graduation design challenges: try to design a board around STM32 MCU that:

• Arduino-compatible form factor,
• Take an 48-pin STM32 microcontroller (since STM32F103CBT6 are that cheap,)
• Bring all I/O pins out somewhere, be it the connectors, JTAG or USB,
• No two pins can be shorted together,
• Use only switch-mode power supply,
• Two layer PCB only,
• Single side load.

This board came out of that challenge, and worked fairly well as a general development board. Also ST doesn't have a Discovery kit for STM32F103 series, this board may serve that purpose too.