141 lines
4.8 KiB
Markdown
141 lines
4.8 KiB
Markdown
# Serial Library
|
|
|
|
The serial library #docs
|
|
|
|
The **serial library** supports [serial communication](https://en.wikipedia.org/wiki/Serial_port) between the BBC micro:bit and another computer. Basically, this allows you to send data from the micro:bit to your own computer. This is very useful for debugging purposes: you can add `write line` statements in your code and see them display on your computer as the program executes.
|
|
|
|
The code below shows a simple script that sends a line when the BBC micro:bit starts and another line each time the button ``A`` is pressed.
|
|
|
|
```
|
|
serial.writeLine("started...")
|
|
input.onButtonPressed("A", () => {
|
|
serial.writeLine("A pressed")
|
|
})
|
|
```
|
|
|
|
## How to read the micro:bit's serial output from your computer
|
|
|
|
Unfortunately, using the serial library requires quite a bit of a setup.
|
|
|
|
### Windows
|
|
|
|
You must install a device driver (for the computer to recognize the serial interface of the micro:bit); then, you must also install a terminal emulator (which is going to connect to the micro:bit and read its output). Here's how to do it:
|
|
|
|
* Follow instructions at https://developer.mbed.org/handbook/Windows-serial-configuration in order to install the device driver
|
|
* Install a terminal emulator; we recommend [Tera Term](https://ttssh2.osdn.jp/index.html.en). At the time of this writing, the latest version is 4.88 and can be downloaded [from here](http://en.osdn.jp/frs/redir.php?m=jaist&f=%2Fttssh2%2F63767%2Fteraterm-4.88.exe). Follow the instructions from the installer.
|
|
|
|
Once both the driver and the terminal emulator are installed, plug in the micro:bit and wait until the device is fully setup. Then, open TeraTerm.
|
|
|
|
* Hit `File` > `New Connection`
|
|
* Check "Serial"; in the dropdown menu, pick the COM port that says "mbed Serial Port". Hit `Ok`.
|
|
* In the menus, hit `Setup` > `Serial Port` and set the baud rate to `115200`.
|
|
|
|
You should be good. Feel free to hit `Setup` > `Save Setup` in the menus to erase the default configuration file with a new one so that you don't have to type in the settings again.
|
|
|
|
Please note that Windows will assign you a different COM port if you plug in another micro:bit. If you're juggling between micro:bits, you'll have to change the COM port every time.
|
|
|
|
### Alternative Windows setup with Putty
|
|
|
|
If you prefer another terminal emulator (such as [PuTTY](http://www.putty.org/)), here are some instructions.
|
|
|
|
* Open Windows's [Device Manager](https://windows.microsoft.com/en-us/windows/open-device-manager); expand the section called "Ports (COM & LPT)"; write down the com number for "mbed Serial Port" (e.g. COM14)
|
|
* Open PuTTY; on the main screen, use the following settings: Serial / COM14 / 115200. Replace COM14 with the COM port number you wrote down previously. Feel free to type in a name and hit "Save" to remember this configuration.
|
|
|
|
|
|
|
|
* (optional): in the "Terminal" section, check "implicit cr in every lf"
|
|
|
|
|
|
|
|
### Linux
|
|
|
|
(Untested).
|
|
|
|
* Plug in the micro:bit
|
|
* Open a terminal
|
|
* `dmesg | tail` will show you which `/dev/` node the micro:bit was assigned (e.g. `/dev/ttyUSB0`)
|
|
* Then, do: `screen /dev/ttyUSB0 115200` (install the `screen` program if you don't have it). To exit, run `Ctrl-A` `Ctrl-D`.
|
|
|
|
Alternative programs include minicom, etc.
|
|
|
|
### Mac OS
|
|
|
|
* Plug in the micro:bit
|
|
* Open a terminal
|
|
* `ls /dev/cu.*` will return to you a list of serial devices; one of them will look like `/dev/cu.usbmodem1422` (the exact number depends on your computer)
|
|
* `screen /dev/cu.usbmodem1422 115200` will open up the micro:bit's serial output. To exit, hit `Ctrl-A` `Ctrl-D`.
|
|
|
|
## Using the serial library in your programs
|
|
|
|
If the ``serial`` button is not available, you will need first to add the ``micro:bit serial`` library to your script:
|
|
|
|
* tap on `add new`
|
|
* tap on `library`
|
|
* select `micro:bit serial`
|
|
|
|
### Writing data
|
|
|
|
This is basically what you will use the serial library for: debugging purposes.
|
|
|
|
* write a number
|
|
|
|
```
|
|
serial.writeNumber(42)
|
|
```
|
|
|
|
* write a string
|
|
|
|
```
|
|
serial.writeString("hello")
|
|
```
|
|
|
|
* write a line of text
|
|
|
|
```
|
|
serial.writeLine("this is a line")
|
|
```
|
|
|
|
Theoretically, you can dump more sophisticated data and then read it back in the event that two micro:bits should be connected to each other over serial. We have not tested this scenario yet as we have yet to expose functionality that allows re-routing the serial ports to the edge connector.
|
|
|
|
* write an image
|
|
|
|
```
|
|
let img = images.createImage(`
|
|
. . . . .
|
|
. # . # .
|
|
. . . . .
|
|
. . . . .
|
|
# # # # #
|
|
`)
|
|
serial.writeImage(img)
|
|
```
|
|
|
|
* write the current screen LED status
|
|
|
|
```
|
|
serial.writeScreen()
|
|
```
|
|
|
|
### Reading data
|
|
|
|
This is useful if you have something connected at the other end. As explained above, this is not yet a scenario.
|
|
|
|
* reads a line of text
|
|
|
|
```
|
|
let msg = serial.readString()
|
|
```
|
|
|
|
* reads an image
|
|
|
|
```
|
|
img = serial.readImage()
|
|
```
|
|
|
|
* reads the state of the screen from serial
|
|
|
|
```
|
|
serial.readScreen()
|
|
```
|
|
|