171 lines
5.6 KiB
Markdown
171 lines
5.6 KiB
Markdown
MicroPython port to Zephyr RTOS
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===============================
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This is a work-in-progress port of MicroPython to Zephyr RTOS
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(http://zephyrproject.org).
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This port requires Zephyr version v3.1.0, and may also work on higher
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versions. All boards supported
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by Zephyr (with standard level of features support, like UART console)
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should work with MicroPython (but not all were tested).
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Features supported at this time:
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* REPL (interactive prompt) over Zephyr UART console.
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* `time` module for time measurements and delays.
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* `machine.Pin` class for GPIO control, with IRQ support.
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* `machine.I2C` class for I2C control.
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* `machine.SPI` class for SPI control.
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* `socket` module for networking (IPv4/IPv6).
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* "Frozen modules" support to allow to bundle Python modules together
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with firmware. Including complete applications, including with
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run-on-boot capability.
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* virtual filesystem with FAT and littlefs formats, backed by either
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DiskAccess or FlashArea (flash map).
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Over time, bindings for various Zephyr subsystems may be added.
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Building
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--------
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Follow to Zephyr web site for Getting Started instruction of installing
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Zephyr SDK, getting Zephyr source code, and setting up development
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environment. (Direct link:
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https://docs.zephyrproject.org/latest/getting_started/index.html).
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You may want to build Zephyr's own sample applications to make sure your
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setup is correct.
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If you already have Zephyr installed but are having issues building the
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MicroPython port then try installing the correct version of Zephyr via:
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$ west init zephyrproject -m https://github.com/zephyrproject-rtos/zephyr --mr v3.1.0
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Alternatively, you don't have to redo the Zephyr installation to just
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switch from master to a tagged release, you can instead do:
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$ cd zephyrproject/zephyr
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$ git checkout v3.1.0
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$ west update
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With Zephyr installed you may then need to configure your environment,
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for example by sourcing `zephyrproject/zephyr/zephyr-env.sh`.
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Once Zephyr is ready to use you can build the MicroPython port just like any
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other Zephyr application. You can do this anywhere in your file system, it does
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not have to be in the `ports/zephyr` directory. Assuming you have cloned the
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MicroPython repository into your home directory, you can build the Zephyr port
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for a frdm_k64f board like this:
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$ west build -b frdm_k64f ~/micropython/ports/zephyr
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To build for QEMU instead:
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$ west build -b qemu_x86 ~/micropython/ports/zephyr
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Consult the Zephyr documentation above for the list of
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supported boards. Board configuration files appearing in `ports/zephyr/boards/`
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correspond to boards that have been tested with MicroPython and may have
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additional options enabled, like filesystem support.
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Running
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-------
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To flash the resulting firmware to your board:
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$ west flash
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Or, to flash it to your board and start a gdb debug session:
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$ west debug
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To run the resulting firmware in QEMU (for BOARDs like qemu_x86,
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qemu_cortex_m3):
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$ west build -t run
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Networking is enabled with the default configuration, so you need to follow
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instructions in
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https://docs.zephyrproject.org/latest/guides/networking/qemu_setup.html#networking-with-qemu
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to setup the host side of TAP/SLIP networking. If you get an error like:
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could not connect serial device to character backend 'unix:/tmp/slip.sock'
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it's a sign that you didn't follow the instructions above. If you would like
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to just run it quickly without extra setup, see "minimal" build below.
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Quick example
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-------------
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To blink an LED:
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import time
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from machine import Pin
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LED = Pin(("GPIO_1", 21), Pin.OUT)
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while True:
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LED.value(1)
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time.sleep(0.5)
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LED.value(0)
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time.sleep(0.5)
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The above code uses an LED location for a FRDM-K64F board (port B, pin 21;
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following Zephyr conventions port are identified by "GPIO_x", where *x*
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starts from 0). You will need to adjust it for another board (using board's
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reference materials). To execute the above sample, copy it to clipboard, in
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MicroPython REPL enter "paste mode" using Ctrl+E, paste clipboard, press
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Ctrl+D to finish paste mode and start execution.
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To respond to Pin change IRQs, on a FRDM-K64F board run:
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from machine import Pin
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SW2 = Pin(("GPIO_2", 6), Pin.IN)
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SW3 = Pin(("GPIO_0", 4), Pin.IN)
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SW2.irq(lambda t: print("SW2 changed"))
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SW3.irq(lambda t: print("SW3 changed"))
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while True:
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pass
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Example of using I2C to scan for I2C slaves:
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from machine import I2C
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i2c = I2C("I2C_0")
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i2c.scan()
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Example of using SPI to write a buffer to the MOSI pin:
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from machine import SPI
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spi = SPI("SPI_0")
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spi.init(baudrate=500000, polarity=1, phase=1, bits=8, firstbit=SPI.MSB)
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spi.write(b'abcd')
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Minimal build
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-------------
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MicroPython is committed to maintain minimal binary size for Zephyr port
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below 128KB, as long as Zephyr project is committed to maintain stable
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minimal size of their kernel (which they appear to be). Note that at such
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size, there is no support for any Zephyr features beyond REPL over UART,
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and only very minimal set of builtin Python modules is available. Thus,
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this build is more suitable for code size control and quick demonstrations
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on smaller systems. It's also suitable for careful enabling of features
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one by one to achieve needed functionality and code size. This is in the
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contrast to the "default" build, which may get more and more features
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enabled over time.
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To make a minimal build:
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$ west build -b qemu_x86 ~/micropython/ports/zephyr -- -DCONF_FILE=prj_minimal.conf
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To run a minimal build in QEMU without requiring TAP networking setup
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run the following after you built an image with the previous command:
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$ west build -t run
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