--- title: "A shared code" subtitle: "micro:bit: talk and play · Talk · Lesson 4" --- # A shared code **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** Morse code, flag signals and the numbers a fast-food counter calls out all work because both sides agree what each code means. :::teacher-note **In one sentence:** Students send a place number that stands for a word in a list both micro:bits share, and see that a message is a code both sides must agree on. **Students should be able to say:** I can send a place number and look up the word it stands for. I can explain why both micro:bits need the same list in the same order. I can step through a list with a button and loop back to the start. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict The receiver shows **get value at receivedNumber**: the word at the place that arrived. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/cb434abb1fc7.png?v=3a0b862809eb78b0) :::keep-together **You press A on one micro:bit, so it sends 2. What does the other micro:bit show?** ☐ Hi ☐ No ☐ Yes ☐ 2 My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** No. The receiver looks up place 2 in its list: Hi is at 0, Yes at 1, No at 2. ::: ## Run Run the program in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Investigate **A** steps through the list; **B** sends the place number of the chosen word. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/98c129ea3961.png?v=5059eba5d8badf69) :::keep-together ### Choose and send **This messenger lets you choose a word with A, then send it with B. Fill in choice after each press of A.** {{rows 1}} | press | choice after | word shown | |---|---|---| | (start) | 0 | | | A | | | | A | | | | A | | | ::: :::teacher-note **Answer:** 1, Yes, 2, No, 0, Hi Each A adds 1. When choice reaches 3 (the length of the list), the if sets it back to 0, so it loops round the list. ::: :::keep-together ### Ella and Tom Ella's list: ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/b48fc8b749f3.png?v=f1c116adf2a66741) Tom's list: ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/85e2f3d04579.png?v=0060d7492e3d079a) **Ella and Tom built the messenger, but Tom's list is in a different order. Ella sends Yes, and Tom's micro:bit shows No. Why?** ☐ Tom's group is wrong ☐ Only the place number is sent, and the same place holds a different word in Tom's list ☐ Lists cannot be sent by radio ☐ The radio changed the number ::: :::teacher-note **Answer:** Only the place number is sent, and the same place holds a different word in Tom's list Ella sends place 1. In her list place 1 is Yes; in Tom's it is No. Both micro:bits must use the same list in the same order. ::: :::keep-together ### Why a number? **Why send the place number instead of the whole word?** ☐ Both micro:bits already have the list, so a small number is all that needs to travel ☐ Radio cannot send words ☐ It is the only block that works ☐ Numbers are prettier ::: :::teacher-note **Answer:** Both micro:bits already have the list, so a small number is all that needs to travel Radio can send words, but a number is shorter and both sides already know what it stands for. That shared list is a code. ::: :::typical ## Modify **One more word.** Add a fourth word. Did you need to change anything else? Why not? **Got it!.** Make the receiver **reply**: when a word arrives, it sends back 99, and the sender shows a tick when 99 arrives. Real messaging apps do this to show "delivered". Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. **One more word:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/2e08478c1da2.png?v=e68168ffcd1aeecf) **Got it!:** ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/556209082bf1.png?v=5b8750eb832f8840) ::: ::: ## Mix it up ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/7c0997fe30b6.png?v=721f97cc118868df) :::keep-together **What does this receiver show for each number that arrives?** {{rows 1}} | receivedNumber | shows | |---|---| | 1 | | | 2 | | | 5 | | ::: :::teacher-note **Answer:** happy face, sad face, cross 5 is more than 3, so the first part runs. 2 is not more than 3, but it is more than 1. 1 is neither, so else runs. ::: ## Make Make a **mood check-in** for the start of class. Each student's micro:bit has a list of moods (at least three). **A** steps through them, **B** sends the chosen one, and the teacher's micro:bit shows it. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} :::teacher-note **One possible solution.** Other correct programs are fine; check that the program runs and does what the task asks. ![The program as blocks](https://studio.learningwaypoints.com/tutorials/_pictures/makecode/code/b7f4ce89d84c.png?v=2669321c88ba72a7) ::: :::wider ## Change a quiz buzzer This buzzer lets you pick an answer, A, B or C, and send it to the quiz master. Add a fourth answer, D, then make the quiz master's micro:bit show a tick after each answer arrives. Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ::: ## Exit ticket :::keep-together **Your micro:bit sends 1. Your list is Hi, Yes, No. Your partner's list is Yes, No, Hi. What does your partner's micro:bit show, and why?** {{lines-3}} ::: :::teacher-note **Answer:** No. Only the place number travels, and place 1 in your partner's list is No. :::