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.. _dev-repl:
==================
Accessing the REPL
==================
REPL (Read-Evaluate-Print-Loop) allows the micro:bit to read and evaluate code
in real-time as you write it.
Accessing the REPL on the micro:bit will require you to:
* Determine the communication port identifier for the micro:bit
* Use a program to establish communication with the device
For versions of Windows before 10 you might need to install the Mbed serial
driver, the instructions for which are found here:
https://os.mbed.com/docs/latest/tutorials/windows-serial-driver.html
Using a serial communication program
------------------------------------
The `Mu Editor <https://codewith.mu/en/tutorials/1.0/repl>`_ has built-in
support for REPL and even includes a real-time data plotter. Some other common
options are `picocom` and `screen`. You will need to install a program and
read the appropriate documentation to understand the basics of connecting to a
device.
Determining the port
--------------------
The micro:bit will have a port identifier (tty, usb) that can be used by the
computer for communicating. Before connecting to the micro:bit we must
determine the port identifier.
**Windows**
When you have installed the aforementioned drivers the micro:bit will appear in
device-manager as a COM port.
**Mac OS**
Open Terminal and type ``ls /dev/cu.*`` to see a list of connected serial
devices; one of them will look like ``/dev/cu.usbmodem1422`` (the exact number
will depend on your computer).
**Linux**
In terminal, type ``dmesg | tail`` which will show which ``/dev`` node the
micro:bit was assigned (e.g. ``/dev/ttyUSB0``).
Communicating with the micro:bit
--------------------------------
Once you have found the port identifier you can use a serial terminal program
to communicate with the micro:bit.
**Windows**
You may wish to use Tera Term, PuTTY, or another program.
In Tera Term:
* Plug in the micro:bit and open Tera Term
* Select Serial as the port
* Go to Setup -> Serial port. Ensure the Port is the correct COM port.
* Choose a baud rate of ``115200``, data 8 bits, parity none, stop 1 bit.
In PuTTY:
* Plug in the micro:bit and open PuTTY
* Switch the Connection Type to Serial
* Ensure the Port is the correct COM port
* Change the baud rate to ``115200``
* Select 'Serial' on the menu on the left, then click 'Open'
**Mac OS**
Open Terminal and type ``screen /dev/cu.usbmodem1422 115200``, replacing
``/dev/cu.usbmodem1422`` with the port you found earlier. This will open the
micro:bit's serial output and show all messages received from the device.
To exit, press Ctrl-A then Ctrl-\\ and answer Yes to the question. There are
many ways back to a command prompt including Ctrl-A then Ctrl-D, which will
detach screen, but the serial port with still be locked, preventing other
applications from accessing it. You can then restart screen by typing
``screen -r``.
**Linux**
Using the ``screen`` program, type ``screen /dev/ttyUSB0 115200``, replacing
``/dev/ttyUSB0`` with the port you found earlier.
To exit, press Ctrl-A then \\ and answer Yes to the question. There are many
ways back to a command prompt including Ctrl-A then Ctrl-D, which will detach
screen. All serial output from the micro:bit will still be received by
``screen``, the serial port will be locked, preventing other applications from
accessing it. You can restart screen by typing ``screen -r``.
Using ``picocom``, type ``picocom /dev/ttyACM0 -b 115200``, again replacing
``/dev/ttyACM0`` with the port you found earlier.
To exit, press Ctrl-A then Ctrl-Q.
|
