9. Chapter 5: Object to Object communication

In this example, micro:bit (sender and receiver) are connected to a channel called “chatroom”.

Peter want to send a smile message to Sally via internet (WAN). Peter’s micro:bit will send a Wi-Fi message “smile” to Sally’s micro:bit. When Sally receive a WiFi message smile, her micro:bit LED will show a smile icon.

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*Before we control the micro:bit, please make sure your micro:bit is connected to the Wi-Fi.

9.1. Receiver side

Goal:

The receiver joins the channel, set the corresponding action when message received.

Step 1: Connect Wi-Fi

Before we join the channel, we need to connect to the network first. We have already known how to connect to the Wi-Fi on the first chapter.

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Step 2: Join the channel

We can let the Micro:bit listening on specific channel to receive the command

  • Snap the on button A+B pressed to stage

  • Put the WiFi Receiver join channel to the on button A+B pressed

  • Type the name of the channel “Chatroom”

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*The user can join more than 1 channel, the maximum is 4.

Step 3: Set the corresponding action

After press the A and B button at the same time, Micro:bit will start listening on channel “chatroom” to wait other people send message to it. We need to use the On WiFi Receiver received to read the command and take action.

  • Snap On WiFi Receiver received to stage

  • If need to received include value message, can use the include value version On WiFi Receiver received at the same time

  • Do the if-condition statement to the variable receivedMessage

  • When the receivedMessage called “smile”, the LED will show a smile icon;

  • When the receivedMessage not called “smile”, the LED will show a sad icon.

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Full Solution

MakeCode: https://makecode.microbit.org/_KbxHgu7xfHhP

You could also download the program from the following website:

Optional:

1. Check channel joined status

When the Receiver was joined the channel, it can check the listening was started successfully or not. The On WiFi channel joined will provide the Error_code for you to determine the result.

  • Go to the OLED Tab

  • Snap initialize OLED … to on Start

  • Snap the On WiFi channel joined to stage

  • Use show string to show the Error_code with channel name

If Error_code is 0, means no error occur
If Error_code is not 0, means error occur
Normally, if no internet connection or the Channel Server is down, the code will be -28674

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2. Show the source channel name of the message

When you join different channels, you may receive same command from each of them alternately, so you need to identify the message is come from which channel. The On WiFi Receiver received provide the variable used to identify.

  • Snap clear OLED display to make sure the display will not overlap.

  • Snap show string to the On WiFi Receiver received

  • Draw the Channel and receivedMessage variable to the show string to display the on OLED

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Full Solution

MakeCode: https://makecode.microbit.org/_ApFMuua7d072

You could also download the program from the following website:

9.2. Sender side

Goal:

The sender can send the message to specific channel

Step 1: Connect WiFi

Before we try to use WiFi Control function, we need to connect to the network, we have already know how to connect to the WiFi on the first chapter.

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Step 2: Send the message

After connected to the internet, we can start send the message to our friend though the channel.

  • Snap the on button … press to stage

  • Snap the WiFi Sender send channel… inside the on button … press

  • Input the correct channel name for your target channel, for example chatroom

  • Input the message which need to be send

  • If need to send the message with value, use another version of WiFi Sender send channel… which include the value input

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Full Solution

MakeCode: https://makecode.microbit.org/_AygdmqgfTCXb

You could also download the program from the following website:

Optional:

Check message sent status:

When the sender sending the message, if use the On WiFi message sent, it can know the sending result of message to channel.

  • Go to OLED Tab

  • Snap the initialize OLED… to on Start

  • Snap the On Wifi message sent to stage

  • Snap the show string inside to On Wifi message sent

  • Snap the clear OLED display to avoid overlap

  • Draw the Status and Error_code variable into the show string text placeholder

If the sending result is success, the Status will be OK and Error_code is 0
If the sending result is fail, the Status will be FAIL with Error_code
Normally, if no internet connection or the channel Server is down, it will be -28674

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Full Solution

MakeCode: https://makecode.microbit.org/_2H1fHvgMv6jg

You could also download the program from the following website: