Controlling the Robotic Arm using the BBC micro:bit · Duplicate the ‘digital write’ block and place it underneath Change the pin from ‘P0’ to ‘P2’ and ‘0’ to ‘1’

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Controlling the Robotic Arm using the BBC micro:bit

You need to plug the BBC micro:bit into a computer using a USB cable – or sync to it using Bluetooth after downloading the correct app from your app store.

This guide assumes you have already done that!!! If you need help, get in contact [email protected]

If you want to use a fifth motor, you will have to connect it to pin 11 and pin 16, when connecting to pin 11, you cannot use Button B

The guide below assumes you are using four motors and not five

Once you have wired up the robotic arm, head over to the BBC micro:bit website: http://microbit.org/ and click on the ‘Let’s Code’ button

Find the ‘JavaScript Blocks Editor (PXT)’ section and click on the ‘Let’s Code’ button

mailto:[email protected]

http://microbit.org/


Click on ‘projects’ ‘new project…’

Next you will need to rename the project so it is easier to locate later on in the activity

Get rid of all the blocks on the page, this can be done by dragging them to the left, over the tabs


Click on the ‘Basic’ tab, select the ‘on start’ block and drag it onto the page

Click on the ‘Variables’ tab, select the ‘set item to’ block and drag it in-between the ‘on start’ block


Click on ‘item’ and rename it to ‘MotorNumber’

Again, click on the ‘Variables’ tab, select the ‘set item to’ block and drag it below the ‘set MotorNumber’ block

Rename the ‘item’ variable to ‘CurrentMotor’

Now we need to stop power going through to the pins when the robotic arm turns on. To do this, click on the ‘Advanced’ tab, then the ‘Pins’ tab, select the ‘digital write pin’ block and place it underneath the ‘set CurrentMotor’ block.


Now we need to add the other seven pins, to do this duplicate the ‘digital write pin’ seven times and place them underneath each other

Next we need to replace the ‘P0’ in each of the statements with the corresponding pins from the wiring diagram previously


Now we need to show the motor number, click on the ‘Basic’ tab, select the ‘show number’ block and place it underneath the ‘digital write’ pin block


Now, click on the ‘Variables’ tab, select the ‘MotorNumber’ block and drag it over the ‘0’ from the ‘show number’ block

Now we need to create a bit of code to select a motor number.

Click on the ‘Input’ tab, select the ‘on button A pressed’ block and drag it onto a blank section of the page

Now, we need to create an ‘if’ statement so that each time button A is pressed it will count up to 6


Click on the ‘Logic’ tab, select the ‘if’ statement and drag it in-between the ‘on button A pressed’ block

Click on the ‘Logic’ tab, select the ‘0=0’ block and place it over the ‘true’ block on the ‘if’ statement


Next click on the ‘Variables’ tab, select the ‘MotorNumber’ block and drag it over the first ‘0’ in the ‘0=0’ block. Then change the second ‘0’ to ‘5’ – this tells the micro:bit that when the variable ‘MotorNumber’ reaches 5 it will run the statements below, in the ‘then’ section

Next, click on the ‘Variables’ tab, select the ‘set item to’ block and drag it into he then section of the ‘if’ statement

Change the ‘item’ to ‘MotorNumber’, then duplicate and place in the else section


Now we need to set the counter. To do this, click on the ‘Math’ tab, select the ‘0+0’ block and drag it over the ‘0’ on the second ‘set MotorNumber to’ block

Click on the ‘Variables’ tab, select the ‘MotorNumber’ block and drag it over the first ‘0’ on the ‘0+0’ block, then change the second ‘0’ to ‘1’

Click on the ‘Basic’ tab, select the ‘show number’ block and drag it underneath the ‘if’ statement


Click on the ‘Variables’ tab, select the ‘MotorNumber’ block, drag and replace the ‘0’ from the ‘show number’ block

Now we need to set button B so that when it is pressed it locks the number so you can move the motor chosen

Click on the ‘input’ tab, select the ‘on button A pressed’ block and drag it onto the page


You will see that the block has now been greyed out, click on the ‘A’ and change it to ‘B’

Next, click on the ‘Variables’ tab, select the ‘set item to’ block an drag it in-between the ‘on button B pressed’ block

Click on ‘item’ and rename to ‘CurrentMotor’


Next, click on the ‘Variables’ tab, select the ‘MotorNumber’ block, drag and replace the ‘0’ from the ‘set CurrentMotor to’ block

We now have created code for button A and button B, next we need to create the code that goes on “behind the scenes”

Click on the on the ‘Basic’ tab, select the ‘forever’ block and drag it onto the page

Next, click on the ‘Logic’ tab, select the ‘if’ statement and drag it in-between the ‘forever’ block


Click on the blue cog and drag an ‘else if’ underneath the if statement to create another section

Click on the ‘Logic’ tab, select the ‘0 < 0’ block and drag it over the ‘true’ block

Now we need to tell the micro:bit that if you tilt it left, the motor will turn left etc.


Click on the ‘Input’ tab, select the ‘acceleration’ block and drag it over the first ‘0’

Now, change the ‘0’ to ‘-300’ – when you are using numbers on the X axis, minus ‘-‘ numbers are for when you want the micro:bit to tilt left and positive numbers are for when the micro:bit tilts right

Now we need to tell the micro:bit to show a directional arrow but also control the motors.

Click on the ‘Basic’ tab, then ‘… More’ and select the ‘show arrow’ block.

Drag the ‘show arrow’ block into the ‘then’ section of the ‘if’ statement

3.


Click on the ‘north’ block and change it to ‘west’ – this changes the arrow so when you tilt the micro:bit left, the arrow will point left or west on a compass

Click on the ‘Logic’ tab, select the ‘if’ statement and drag it underneath the ‘show arrow’ block

Click on the blue cog icon located on the ‘if’ statement


Now drag the else if block underneath the ‘if’ block on the right. Repeat two more times to have a total of 3 ‘else if’ blocks

Now we need to tell the micro:bit to move the robotic arm motors, to do this we define a variable for each motor.

Click on the ‘Logic’ tab, select the ‘0=0’ block, drag and drop it to the right of the if statement, replacing the ‘true’ block


Click on the ‘Variables’ tab, select the ‘CurrentMotor’ block and drag it over the first ‘0’ on the ‘0=0’ statement

Change the second ‘0’ to ‘1’ – this statement tells the micro:bit, that if the motor selected with button B is number 1 then run the code we are going to put in the ‘then’ section


Next, click on the ‘Advanced’ tab, then the ‘Pins’ tab. Select the ‘digital write pin’ block and drag it into the first ‘then’ section of the ‘if’ statement

Duplicate the ‘digital write’ block and place it underneath


Now we need to change the pin number and the value of the pins

Change the ‘0’ in the first ‘digital write pin’ block to ‘1’, then change the Pin on the second ‘digital write’ block to ‘P1 – this will move the base motor left

Now we need to create the second motor function

Duplicate the ‘CurrentMotor = 1’ block, drag and snap into place on the right of the first ‘else if’ section

Change the ‘1’ to ‘2’


Next, click on the ‘Advanced’ tab, then the ‘Pins’ tab. Select the ‘digital write pin’ block and drag it into the second ‘then’ section


Change the pin from ‘P0’ to ‘P8’ and ‘0’ to ‘1’ on the first ‘digital write’ statement.


Next, change the pin from ‘P0’ to ‘P12’ on the second ‘digital write’ statement – this will create a section of code to control the second motor

Duplicate the ‘CurrentMotor = 2’ block, drag and snap into place on the right of the second ‘else if’ section

Replace the ‘2’ with ‘3’


Next, click on the ‘Advanced’ tab, then the ‘Pins’ tab. Select the ‘digital write pin’ block and drag it into the third ‘then’ section


Change the pin from ‘P0’ to ‘P2’ and ‘0’ to ‘1’ on the first ‘digital write’ block, then change the pin to ‘P13’ on the second ‘digital write’ block – this creates the block of code to control the third motor


Duplicate the ‘CurrentMotor = 3’ block, drag and snap into place on the right of the third ‘else if’ section

Replace the ‘3’ with ‘4’

Next, click on the ‘Advanced’ tab, then the ‘Pins’ tab. Select the ‘digital write pin’ block and drag it into the fourth ‘then’ section



Change the pin from ‘P0’ to ‘P14’ and ‘0’ to ‘1’ on the first ‘digital write’ block, then change the pin to ‘P15’ on the second ‘digital write’ block – this creates the block of code to control the fourth motor

Now we need to create a block of code so when the micro:bit tilts right the motors turn anticlockwise


Click on the ‘Logic’ tab, select the ‘0 < 0’ block and drag it to the right of the ‘else if’ on the first ‘if’ statement

Click on the ‘Input’ tab, select the ‘acceleration’ block and drag it over the first ‘0’ on the ‘0 < 0’ statement

Next, change the ‘<’ symbol to ‘>’, then ‘0’ to ‘300’

Duplicate the whole ‘if’ statement located in the first ‘then’ section and place it below the ‘acceleration > 300’ block


Next, we need to change the pin numbers so when the micro:bit tilts left, the motors turn the opposite direction. All that is needed here is to change the ‘1’s to ‘0’s and the ‘0’s to ‘1’s

Now, most of the code is done, all that is left to do is to add code into the ‘else’ section so when the micro:bit is not doing any of the previous code it will stop all motors

Click on the ‘Basic’ tab, select the ‘show leds’ block and drag it into the ‘else’ section


Now we need to create a plus sign in the ‘show leds’ block, to do this, click on the individual boxes until you make a ‘+’ shape

Now we need to make sure the pins we use are turned off.

Click on the ‘Advanced’ tab, then the ‘Pins’ tab. Select the ‘digital write’ block and drag it below the previously placed ‘show leds’ block


Repeat the above step, seven more times

Now, change the pins on all eight ‘digital write’ blocks to the micro:bit pins used to control the motors (see image below)


You now will have all the code to control the Robotic Arm using a micro:bit

You can now download the code to the micro:bit or use the ‘Downloading code to the BBC micro:bit’ guide on the next page if you are unsure

Downloading code to the BBC micro:bit


On the bottom left of the PXT editor is a button that says 'Download' - shown below in a red box, click on it to save the code file

Click on the downloaded file at the bottom of the browser - select 'Show in Folder'

This will open the folder containing all your downloaded files - this will include a file called something like 'microbit-micro-bit-Robotic-Arm.hex'


Right click on the file and choose to copy it (this is ready for the next step), now you need to plug the micro:bit, into your computer

Right click on a blank space within the micro:bit folder and choose 'Paste' - it will display a window a bit like the below as it copies the file to the micro:bit.

The code has now downloaded, have fun playing with the micro:bit Robotic Arm!!

Documents

Controlling the Robotic Arm using the BBC micro:bit · Duplicate the ‘digital write’ block and place it underneath Change the pin from ‘P0’ to ‘P2’ and ‘0’ to ‘1’