========
Maix Bit
========

.. tags:: experimental, arch:risc-v, chip:k210, vendor:sipeed

.. figure:: maix-bit.png
   :figwidth: 50%
   :align: center
   :alt: The Maix Bit development board.

   The Maix Bit development board.

The Maix Bit is a RISC-V AI IoT development board.

Features
========

* K210 RISC-V AI Chip
* Dual-core
* Independent FPU
* 64-bit
* 8MB on-chip SRAM
* Double precision FPU with multiplication, division and square root

.. warning::

   There is currently no support for the FPU, or RISC-V User mode. Peripherals
   such as GPIO, SPI and I2C are also currently unsupported.

.. todo::

   If you are interested in using this board, please consider contributing
   implementations for the above missing features.

Installation
============

1. Download and install toolchain and openocd-k210

   .. code:: console

      $ curl https://static.dev.sifive.com/dev-tools/riscv64-unknown-elf-gcc-8.3.0-2019.08.0-x86_64-linux-ubuntu14.tar.gz
      $ export PATH=$PATH:/$TOOL_CHAIN_PATH/bin

2. Build openocd-k210

   .. code:: console

      $ git clone https://github.com/kendryte/openocd-kendryte
      $ cd openocd-kendryte
      $ ./bootstrap & ./configure & make


Flashing
========

Download and run NuttX from SRAM (not SPI-Flash):

.. code:: console

   $ picocom -b 115200 /dev/ttyUSB0
   $ sudo ./src/openocd -s ./tcl -f ./tcl/kendryte.cfg -m 0
   $ riscv64-unknown-elf-gdb ./nuttx
   (gdb) target extended-remote :3333
   (gdb) load nuttx
   (gdb) c

Write ``nuttx.bin`` to SPI-Flash:

.. code:: console

   $ pip3 install kflash
   $ kflash -p /dev/ttyUSB0 -b 1500000 ./nuttx/nuttx.bin

.. note::

   The ``kflash_gui`` is not recommended because it's unstable.

Configurations
==============

Configurations can be selected using the following configure tool command:

.. code:: console

   $ ./tools/configure.sh maix-bit:<config>

Where ``<config>`` can be replaced by the name of any configuration listed
below.

nsh
---

A simple configuration with NSH running.