The Spresense project consists of a Arduino compatible board with Sony’s high performance CXD5602 micro-controller. The CXD5602 has built-in GPS and high-resolution audio capabilities.
The main board uses a processor developed by Sony for IoT and sensing applications. The main board can be operated alone or with the extension board.
The Spresense uses Sony’s new chipset on the main board: * The CXD5602 System on Chip (SoC) multi core processor with GNSS * The CXD5247 power management and audio analog interface chip
The Spresense extension board is a board which extends the interfaces compared to the Spresense main board. The Spresense main board and the Spresense extension board are connected by a Board-to-Board (B-2-B) connector. The Spresense extension board has Arduino Uno pin compatible shape and pin socket locations. However, there are some differences compared to the Arduino Uno.
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This is the latest stable release of CircuitPython that will work with the Spresense.
Start here if you are new to CircuitPython.
This is the latest unstable release of CircuitPython that will work with the Spresense.
Unstable builds have the latest features but are more likely to have critical bugs.
Built-in modules available: 
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. Try them if you want the absolute latest and are feeling daring or want to see if a problem has been fixed.
All previous releases are listed on GitHub, with release notes, and are available for download from Amazon S3. They are handy for testing, but otherwise we recommend using the latest stable release. Some older GitHub release pages include the same binaries for downloading. But we have discontinued including binaries as assets on newer release pages because of the large number of files for each release.