micro:bit click adapter - DIY distance reader

BBC's micro:bit has proved itself to be a perfect educational tool in the field of embedded development.

Katarina, of whom we wrote about multiple times, actually has a lot of experience with teaching kids about programming and embedded development. So, she was happy to make a few examples for our new shield - micro:bit click adapter.

So, Katarina is going to lead you through all the necessary steps of making your own micro:bit application. We gave it our best to make this article understandable for beginners and easy to follow. But we feel it's important to add that with micro:bit and the micro:bit click adapter it's possible to make more complex projects using more peripherals (SPI, I2C, UART). In this article, we will be using just I2C and PWM.

Watch our video about the micro:bit and the micro:bit click adapter to see how the project looks like in real life. Biljana even did a small intro so you get the basic information about these products.

Hardware requirements

• micro:bit
• micro:bit click adapter
• Proximity 2 click
• Buzz click

Place the micro:bit into the adapter then put the Proximity 2 click into the mikroBUS A and Buzz click into the mkroBUS B.

Software requirements

The Makecode maker is available online:

makecode.microbit.org

Get set - ready - go

The idea behind this project is to implement a "distance reader" on the micro:bit click adapter, by using Proximity 2 click. On the video we have prepared for you, you'll see how the whole thing works. Depending on the distance of one's hand, for example, and with the help of Buzzer click, you'll hear an appropriate sound. The closer you get to the sensor on Proximity 2 click the higher the sound on Buzz 2 click. The LED matrix on the micro:bit has been programmed to correspond with the sound of the Buzz click and the distance of your hand to the Proximity 2 click's sensor.

The makecode editor itself offers the possibility of programming using blocks and using javascript editor. It will be necessary to create a custom module, for our application.

To make a new custom module:

1. Go to JavaScript editor
2. Click on the Explorer view and expand it
3. Click on the + button that just appeared and add a custom.ts file in your project. Next, inside our custom.ts file we can add a function specifically for Proximity 2 click. Let’s start with the functions which are needed to initialize Proximity 2 click sensor.

Your custom.ts file should look like this.

namespace custom {
   //% block
   export function receive_config(): void
   {
       let buf = pins.createBuffer(2)
       buf.setNumber(NumberFormat.UInt8LE, 0, 0x02)
       buf.setNumber(NumberFormat.UInt8LE, 1, 0xF1)
       pins.i2cWriteBuffer(0x4A, buf, false)
   }
   //% block
   export function transmit_config(): void
   {
       let buf = pins.createBuffer(2)
       buf.setNumber(NumberFormat.UInt8LE, 0, 0x03)
       buf.setNumber(NumberFormat.UInt8LE, 1, 0x0F)
       pins.i2cWriteBuffer(0x4A, buf, false)
   }
   //% block
   export function main_config(): void
   {
       let buf = pins.createBuffer(2)
       buf.setNumber(NumberFormat.UInt8LE, 0, 0x01)
       buf.setNumber(NumberFormat.UInt8LE, 1, 0x13)
       pins.i2cWriteBuffer(0x4A, buf, false)
   }
}

Let’s say that this is the default configuration for the Proximity 2 click. If you are interested what exactly each of these functions does, the datasheet for the MAX44000 is the place that offers answers.

Now we need to make the function which will read the distance from Proximity 2 click and play the tones on the Buzzer click, depending on the distance, but also power on the appropriate LEDs on the micro:bit built-in matrix.

You can add this function inside the custom.ts, below or above the previous ones.

//% block
   export function myTask(): void   {
       let buf = pins.createBuffer(1)
       let distance = 0
       let duration = 50
       pins.analogSetPitchPin(AnalogPin.P0)
       buf.setNumber(NumberFormat.UInt8LE, 0, 0x16)
       pins.i2cWriteBuffer(0x4A, buf, false)
       buf = pins.i2cReadBuffer(0x4A, 1, false)
       distance = 255 - buf.getNumber(NumberFormat.UInt8LE, 0)

       if (distance < 20) {
           pins.analogPitch(3920, duration)
           basic.showLeds(`. . . . .
                           . . . . .
                           . . . . .
                           . . . . .
                           # # # # #`)
       }
       else if (distance > 20 && distance < 120) {
           pins.analogPitch(1760, duration)
           basic.showLeds(`. . . . .
                           . . . . .
                           . . . . .
                           # # # # #
                           . . . . .`)
       }

       else if (distance > 120 && distance < 160) {
           pins.analogPitch(880, duration)
           basic.showLeds(`. . . . .
                           . . . . .
                           # # # # #
                           . . . . .
                           . . . . .`)
       }

       else if (distance > 160 && distance < 250) {
           pins.analogPitch(440, duration)
           basic.showLeds(`. . . . .
                           # # # # #
                           . . . . .
                           . . . . .
                           . . . . .`)
       }

       else if (distance > 250) {
           pins.analogPitch(110, duration)
           basic.showLeds(`# # # # #
                           . . . . .
                           . . . . .
                           . . . . .
                           . . . . .`)
       }
   }

This function actually reads the distance value from the 0x16 register using I2C communication and checks if the distance is in any of the offered range. If the distance is smaller the tone frequency will be higher. We used the PWM frequency to adjust the sound frequency.

These four functions will be enough for us to finish the demo using the makecode graphical code block editor, so let’s go back to the graphical interface. You will see that below the basic button we have a new “Custom” button. Click it and you will see that you can select any of function that we previously defined inside the javascript code.

Now let’s add the “configuration” functions to the “on start” container and our task function to the “forever” container.

That’s it, we can now click on the download button and upload the hex file to our micro:bit board.

The uploading is nothing more than the copying of the file inside DAPLINK device which should appear any time we turn on our device.

Conclusion

Now it's time for you to go and go try it out for yourself. "Trial and error" is one of the best ways to learn, so don't get discouraged if you don't succeed on your first try.

With a detailed tutorial like this one, all you need is some practice.