Send data to the computer

Classroom resources

Load these into Waypoints Prepare: choose Load URL and paste the copied address, or download the file and import it. In Prepare, the worksheet's Teacher edition shows the answers; the student copy hides them.

• Slides Download Copy address for Prepare Present from the browser, or export to PowerPoint or PDF.
• Worksheet Download Copy address for Prepare Print the student copy; the Teacher edition has the answers.

Students will be able to

• I can send a sensor reading to the computer again and again.
• I can explain what travels down the cable (a named line of text).
• I can send two values and choose how often they are sent.

Timing

Predict and Run 8 min · On a real micro:bit 8 min (typical) · Investigate 8 min · Modify 10 min · Make 10 min

Before class

The idea: a micro:bit plugged into a computer can send text down the USB cable, one line at a time (this is called serial). serial write value sends a line such as light:128: a name, a colon and a number. Whatever is on the other end (MakeCode's Show data, the board in this lesson, a spreadsheet) turns those lines into a table or a graph.

Without micro:bits: the MakeCode simulator shows the values under Show data, so every required step works in the browser. The board step ("On a real micro:bit") is optional and needs a micro:bit, a data USB cable and Chrome or Edge.

With micro:bits: students download the program, leave the micro:bit plugged in, and click Connect a micro:bit on the board. Only one page can use the cable at a time, so if MakeCode is connected to the micro:bit, disconnect it there first.

Running the lesson

1. Predict: most say a graph. Ask: who draws the graph, the micro:bit or the computer?
2. Run: Show data appears under the simulator once values arrive.
3. On a real micro:bit: covering it and shining a torch makes a clear graph.
4. Investigate: Ben's logger is the on start versus forever slip from Foundations.

The hard part (on purpose)

The text format links the micro:bit and the board. When nothing shows, ask whether the program is running and the write block is inside forever.

When students get stuck

Answers to the checks

1. Predict: This program runs on a micro:bit plugged into a computer. What arrives at the computer every half second?
   A line of text: the name light, a colon, and the reading. The computer draws the graph from the lines; the micro:bit only sends text.
2. On a real micro:bit: Download the program to a micro:bit, connect it, and collect at least 10 light readings.
   
3. Names: Why does each line start with a name (light:)?
   So the computer can tell different values apart when there are several
   With light:128 and temperature:21 arriving on the same cable, the name says which is which. The graph draws one line per name.
4. No pause: You delete the pause. What happens?
   Readings pour out as fast as the micro:bit can send them, far more than you need
   Forever repeats as fast as it can. The pause sets how many readings a second you get: 500 ms is two a second.
5. Ben's logger: Ben's program sends one reading when the micro:bit starts, then nothing. Why?
   The block is in on start, not in forever, so it runs only once
   A logger has to read and send again and again: the send goes in forever, with a pause.

Solutions

One possible solution for each task. Other correct programs are fine.

Modify › Two values

basic.forever(function () {
    serial.writeValue("light", input.lightLevel())
    serial.writeValue("temperature", input.temperature())
    basic.pause(500)
})

Modify › Faster

basic.forever(function () {
    serial.writeValue("light", input.lightLevel())
    basic.pause(100)
})

Make

basic.forever(function () {
    serial.writeValue("x", input.acceleration(Dimension.X))
    serial.writeValue("y", input.acceleration(Dimension.Y))
    basic.pause(200)
})
input.onButtonPressed(Button.A, function () {
    serial.writeLine("mark")
})

Stretch and support

Stretch: Send the sound level too, and find out which is noisier: the classroom or the corridor.

Support: Give the Make program with x done; students add y and the button.

Exit ticket

What does the computer receive when the micro:bit runs serial write value light, light level?

A line of text: the name light, a colon and the reading, such as light:128.

What each step is for

• On a real micro:bit: The same lines arrive from a real micro:bit, and a different program (this board) can graph them: the text format is what connects the two.
• Investigate: Each reading is a named line of text sent again and again; the name tells values apart and the pause sets how often a reading is sent.
• Modify: A second named value appears as its own line on the graph; changing the pause changes how often readings arrive.

Where it leads

Next: the computer sends commands to the micro:bit. Real world: data loggers in science labs, weather stations and fitness trackers.