by Sean Cross (xobs)
Only 13mm long, Fomu really puts the micro in microprocessor. Fomu is a fully open-source, programmable FPGA device that sits inside a USB Type-A port. It has four buttons, an RGB LED, and an FPGA that is compatible with a fully open source chain and capable of running a RISC-V core. Fomu comes in a custom plastic enclosure that slots perfectly into a USB port.
- has Python
- With 128 kilobytes of RAM and a large amount of storage, Fomu is powerful enough to run Python natively. And since it lives in your USB port, installation is super simple. FPGAs are complicated, but the latest Python tools make it easy to use Fomu without any specialized training.
- runs RISC-V
- Underneath the Python interpreter lies a RISC-V softcore running on the FPGA fabric. RISC-V is an up-and-coming processor architecture that is poised to take over everything from deeply-embedded chips to high-performance computing. Fomu’s RISC-V softcore is a great introduction to the processor architecture of the future.
- is an FPGA
- An FPGA is a piece of reconfigurable silicon. The default Fomu firmware exposes a USB bootloader running a RISC-V softcore, but you can load whatever you want. Softcores are also available for LM32 and OpenRISC. You can practice adding instructions to the CPU, or add new blocks such as LED blink patterns or better captouch hardware blocks.
- is entirely open
- Developing with Fomu is incredibly easy: just load code via USB and go. Whether you’re writing RISC-V code, Python code, or HDL, it’s all uploaded to Fomu in the same way. The ICE40UP5K FPGA is supported with a fully open toolchain, meaning you can start development without creating an account, signing an NDA, or downloading a multi-gigabyte installer. An FPGA is an Array of Gates that is Field-Programmable. When you buy a chip such as a CPU, the logic cells are all fixed in place. A CPU can run any amount of code, but if you want to do anything exotic you need to create software and, depending on what you want to do, that software can be very slow.
For example, many embedded projects use WS2812 LEDs such as NeoPixels that require a specialized timing signal. A CPU can generate this signal in software, but it can’t do anything in the background while talking to the light. If the string of LEDs is very long, then the CPU wastes a lot of time and power generating the signal.
With an FPGA, it becomes possible to create an “LED driver” that allows the CPU to keep running while a hardware component handles the timing. The CPU could do other work, or could put itself in a low power state.
In fact, the “CPU” in the FPGA is created from a hardware description language, meaning it can be modified or swapped out. If you wanted, you could create a brand-new CPU instruction. Do you want to have fast 64-bit multiplies? Or maybe you want a way to get random numbers easily? With Fomu and its FPGA, you have the source code to the CPU itself.
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This is the latest stable release of CircuitPython that will work with the Fomu.
Use this release if you are new to CircuitPython.
Built-in modules available: _asyncio, _pixelmap, adafruit_pixelbuf, aesio, array, atexit, binascii, builtins, builtins.pow3, busio.SPI, busio.UART, collections, digitalio, errno, getpass, io, json, keypad, keypad.KeyMatrix, keypad.Keys, keypad.ShiftRegisterKeys, math, microcontroller, msgpack, neopixel_write, os, os.getenv, rainbowio, random, re, select, storage, struct, supervisor, sys, time, touchio, traceback, ulab, usb_cdc, usb_hid, usb_midi, zlib
This is the latest development release of CircuitPython that will work with the Fomu.
Alpha development releases are early releases. They are unfinished, are likely to have bugs, and the features they provide may change. Beta releases may have some bugs and unfinished features, but should be suitable for many uses. A Release Candidate (rc) release is considered done and will become the next stable release, assuming no further issues are found.
Please try alpha, beta, and rc releases if you are able. Your testing is invaluable: it helps us uncover and find issues quickly.
Built-in modules available: _asyncio, _pixelmap, adafruit_pixelbuf, aesio, array, atexit, binascii, builtins, builtins.pow3, busio.SPI, busio.UART, collections, digitalio, errno, getpass, io, json, keypad, keypad.KeyMatrix, keypad.Keys, keypad.ShiftRegisterKeys, locale, math, microcontroller, msgpack, neopixel_write, os, os.getenv, rainbowio, random, re, select, storage, struct, supervisor, sys, time, touchio, traceback, ulab, usb_cdc, usb_hid, usb_midi, warnings, zlib
Every time we commit new code to CircuitPython we automatically build binaries for each board and language. The binaries are stored on Amazon S3, organized by board, and then by language. These releases are even newer than the development release listed above. Try them if you want the absolute latest and are feeling daring or want to see if a problem has been fixed.
Previous Versions of CircuitPython
All previous releases of CircuitPython are available for download from Amazon S3 through the button below. For very old releases, look in the OLD/ folder for each board. Release notes for each release are available at GitHub button below.
Older releases are useful for testing if you something appears to be broken in a newer release but used to work, or if you have older code that depends on features only available in an older release. Otherwise we recommend using the latest stable release.