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# Which message?
micro:bit: talk and play · Talk
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## Today
**We are learning to** use the number that arrives by radio to do something different for each message, and send words as well as numbers.
- I can make the receiver do something different for each number that arrives.
- I can send a word by radio and show it.
- I can agree a code of numbers with a partner.
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## Why it matters
> A garage door opener has one receiver but two buttons: open and close. The receiver reads which code arrived and acts on it.
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💬 Discussion
## Predict
**You press B on the first micro:bit. What does the second micro:bit show?**
- A heart, then a sad face
- A sad face
- The number 2
- A heart
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✅ Check
## What happened?
* A sad face. B sends 2. On the second micro:bit receivedNumber is 2, so the first question is false and the else if part runs.
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✍️ Activity
## Run it
Open the lesson at this step and try it together.
[studio.learningwaypoints.com/tutorials/code/microbit-play/microbit-which/?full=step-2#step-2](https://studio.learningwaypoints.com/tutorials/code/microbit-play/microbit-which/?full=step-2#step-2)
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💬 Discussion
## Investigate
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✅ Check
## Trace the messages
**What does the receiver show for each number that arrives?**
| receivedNumber | shows |
|---|---|
| 1 | ? |
| 2 | ? |
| 5 | ? |
* Answer: heart, sad face, nothing
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✅ Check
## Max's second block
**Max wants 1 to show a heart and 2 a sad face. He drags in a second on radio received block for 2, and it greys out. What should he do?**
- Put the second block in forever
- Send 2 twice
- Use one on radio received, with if receivedNumber = 1 … else if receivedNumber = 2
- Use a different group for 2
* Answer: Use one on radio received, with if receivedNumber = 1 … else if receivedNumber = 2
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✅ Check
## In Python
```python
def on_received_number(receivedNumber):
if receivedNumber == 1:
basic.show_icon(IconNames.HEART)
elif receivedNumber == 2:
basic.show_icon(IconNames.SAD)
radio.on_received_number(on_received_number)
```
`elif` is Python's short way to write *else if*.
**The receiver in Python. Match each line with what it does.**
| | |
|---|---|
| `def on_received_number(receivedNumber):` | A. runs for every number that arrives |
| `if receivedNumber == 1:` | B. checks whether the number was 1 |
| `elif receivedNumber == 2:` | C. otherwise, checks whether it was 2 |
* Answer: def on_received_number(receivedNumber): → A. runs for every number that arrives; if receivedNumber == 1: → B. checks whether the number was 1; elif receivedNumber == 2: → C. otherwise, checks whether it was 2
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✍️ Activity
## Agree a code (4 min)
Pairs agree what 1, 2 and 3 mean (left, right, stop). One holds up fingers silently; the other acts it out.
---
✍️ Activity
## Modify
- **A third message:** Make a **shake** send 3, and the receiver show a surprised face when 3 arrives.
- **Send a word:** **send string** sends a word, and **on radio received receivedString** holds the word that arrived. Make **A+B** send *hi*, and the receiver show it.
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit-play/microbit-which/?full=step-4#step-4)
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💬 Discussion
## Investigate: Mix it up
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✅ Check
## Mix it up
**Three micro:bits run this program. The first and second are in group 1; the third is in group 2. You press A on the first. Which show the heart?**
- All three
- Only the second
- Only the first
- The second and the third
* Answer: Only the second
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✍️ Activity
## Make
Make **bike signals by radio**: the rider presses buttons on one micro:bit, and the one on the back of the bike shows the signal.
- **A** sends 1: left arrow.
- **B** sends 2: right arrow.
- **Shake** sends 3: a stop picture.
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit-play/microbit-which/?full=step-6#step-6)
---
✍️ Activity
## Change a doorbell
This doorbell sends a **word** instead of a number. Make it send your name, then make **B** send a different message, such as "come in".
[Open this step](https://studio.learningwaypoints.com/tutorials/code/microbit-play/microbit-which/?full=step-7#step-7)
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✍️ Activity
## Ride along (3 min)
One partner is the rider, the other the back light. The rider sends a signal; the back light calls out what it shows.
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✅ Check
## Exit ticket
**A receiver checks if receivedNumber = 1 and else if receivedNumber = 2. What happens when 3 arrives?**
* Nothing. Both questions are false and there is no else.