Bit:2:Pi Control Raspberry Pi Addon Boards with your Micro:Bit

Bit:2:Pi Control Raspberry Pi Addon Boards with your Micro:Bit

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[Click on any image to enlarge]

Purchase >HERE<

Overview

Bit:2:Pi (Pronounced Bit – to – Pie) is a connector and power management system that allows you to plug in a Micro:Bit at one end and a Raspberry Pi addon board (26-pin or 40-pin, HAT, pHAT or other) at the other end.

In between there are some breakout and connection headers that enable you to customise how the two boards are connected.

The power on the board is managed so that:

  1. Any or all power sources can be connected safely at the same time
  2. The Micro:Bit is never used to power the Raspberry Pi HAT (this is true for Bit:2:Pi v1.0 or later)
  3. Power for the HAT is provided either by the micro-USB connector at the HAT end, or by an attached battery holder
  4. The On/Off power switch controls the power to the HAT as well as to the Micro:Bit
  5. The “5V” signal on the HAT connector is actually from the battery or the micro-USB. If using the battery, this is likely to be around 4.5 to 4.8V using alkaline batteries, or 3.6 to 4.0V using rechargeable batteries. Not all HATs will work at these voltages.

To control the Raspberry Pi addon board (shortened to “HAT” from now on), you must write some code for the BBC Micro:Bit:

  • Many HATs are simply setting GPIO pins High or Low and for these you can use any available language easily. Simply set the Micro:Bit pin corresponding to the HAT GPIO pin (as determined by the various jumpers)
  • Some HATs use neopixels (eg. PlayHAT or Unicorn HAT). These require the neopixels to be driven by GPIO18 (physical Pin 12). By default, this is Pin 2 on the Micro:Bit
  • Some HATs require I2C commands (eg. Picon Zero). You can use the standard I2C commands within Micro:Bit to send and receive the necessary data. The default configuration connects the I2C pins
  • Some HATs require SPI connections (eg. various Analog boards using the MCP3008 or similar). Again the SPI pins are connected by default

 

Configuration

The male header block closest to the Micro:Bit (labelled MBit/RPi in v1.0) is where most of the configuration is done.

The MBit side of the header is labelled with the Micro:Bit pin numbers and the RPi side of the jumper is numbered with the GPIO names (Broadcom names)

The Bit:2:Pi is supplied with 13 little black jumpers that connect across from the MBit side to the RPi side. This gives the default settings as follow:

Micro:Bit Pin

GPIO Pin

Physical Pin

0

04

7

1

17

11

2

18

12

8

27

13

12

22

15

16

23

16

5

24

18

11

25

22

13

SCL

5

14

MISO

21

15

MOSI

19

19

SCLK

23

20

SDA

3

If you need to connect something differently, then simply remove the appropriate black jumper(s) and use a short Female-Female dupont wire to connect theMicro:Bit pin(s) to the appropriate Raspberry Pi pins.

 

Example Boards

[this section requires tested boards with example code – contributions welcome]

Some tested working boards are:

 

External Contributors

Several people have written some software for the Micro:Bit to work with Raspberry Pi addon boards using the Bit:2:Pi adaptor. Many thanks go out to these contributors!

 

Michael Rimicans (Twitter @heeedt)

 

Neil Avery (Twitter @veryalien)

 

Les Pounder (Twitter @biglesp)

 

 Mark Atkinson (www.multiwingspan.co.uk)

 

 

Robo:Bit Mk2 Robotics Controller and Buggy for Micro:Bit

Robo:Bit Mk2 Robotics Controller and Buggy for Micro:Bit

IMG_0904a

Looking for Robobit Mk3 ? Then Visit this Page

Robo:Bit Mk2 is a general purpose robotics controller for the BBC Micro:Bit, that also converts easily into a self-contained little buggy.

Purchase Robo:Bit here

Purchase the Robo:Bit Buggy here

Overview

The Robo:Bit controller has the following features

  • Ready assembled (NB. headers for the underside are not fitted unless the complete buggy is purchased, but they are included in case you want to add these)
  • Edge connector for easy attachment of your BBC Micro:Bit
  • Dual motor driver with full control of each motor for both direction and speed (uses DRV8833)
  • 3.3V Regulator to power the BBC Micro:Bit
  • Power On/Off switch with LED indicator
  • Mounting holes for either 3-cell or 4-cell AA battery holder
  • Front interface for ultrasonic distance sensor (simply push-fit an HC-SR04, or solder for added security) [NB. You can also plug the McRoboFace into here directly and it will work as required!]
  • 7 of the Micro:Bit pins are broken out to a header with GVS connections (Ground, Volts, Signal) for ease of connecting external devices and sensors
  • I2C signals broken out in case you want to add more complex peripherals

Warning: The line follower sensors share the same pins as the buttons. Depending what language you are using, when the Micro:Bit is started or reset it will check the 2 buttons and start pairing if they are both pressed. With the Robobit, this translates to both line follower sensors getting reflections. You can stop it happening by lifting it off the surface before switching on, or of course disconnecting one or both of the sensors

Software & Programming

Robo:Bit uses the same connections for the motors as Bit:Bot, so most of the software will continue to work.

{{OLD INFO:  In particular, the BitBot package for Microsoft PXT works fine (but you cannot use the sonar or neopixel blocks from this package as they use the wrong pins for RoboBit). To use this package, load up microsoft PXT for Micro:Bit from here, then go to Advanced or Tools and select Add package. Then search for “BitBot”.}}

Please use the currently Beta Robobit package. for Microsoft Makecode (aka PXT). Select Advanced, then “Add Package”. Into the search bar, put this URL: https://github.com/4tronix/Robobit and the Package will show as an Orange Taxi icon on the left.

The Pins are used as follows:

  • Left Motor: Pin 0 (PWM) and Pin 8 (Direction)
  • Right Motor: Pin 1 (PWM) and Pin 12 (Direction)
  • Ultrasonic detector: Pin 13 (alternatively neopixel output pin)
  • Left line sensor: Pin 11 (bottom 3×2 header)
  • Right Line sensor: Pin 5 (bottom 3×2 header)

For each motor there is a 2-pin screw terminal and a 2-pin male header. If fitted, there is also a 2-pin JST header underneath the board (used in the buggy). All three connectors for each motor are connected together.

Some sample PXT programs. Click on them to download the compressed HEX files. You can install them into your Makecode environment by selecting Projects and “Import File” and browsing to the HEX file on your PC

 

Motor Test

Simply moves forward and backwards to check the motors are connected OK

 

Sonar test with the Ultrasonic

Simply displays the distance measurement on the MicroBit

 

FollowMe Sonar Test

The Robot will move to within 15-20cms of an obstacle and then move forwards or backwards to stay within this range

 

Control your Robobit Buggy from another Microbit

The same code can be loaded into each microbit. The one on the buggy will receive the commands from the second one – in your hand. To load this code, copy the compressed HEX file from here onto your PC, and uncompress it. Then, from Makecode, select Project and browse to find where you put the HEX file. Install this onto both the controller and the buggy. Here is the complete code visually:

Assembling the Robo:Bit Buggy

STOP: Before continuing, please check which version of RoboBit you have as the assembly instructions differ. The version number is written on the underside of the PCB as v1.0 or v1.1 or v2.0

Note that this buggy can be purchased in modular form. You can use your own motors and wheels if you already have them – the little yellow motors are pretty ubiquitous, so many schools and hobbyists will already have them. This guide to assembly assumes you have purchased the complete kit, including the ready-soldered wires on the motors – if not you would have to connect the wires to the motors and use the screw terminals on the top of the board.

Click on the image below for a quick assembly GIF

IMG_0898a

 

Step 1. Check you have all the Parts

NB. These are different for each Version. Check the PCB version (written on the underside of the PCB) before continuing

IMG_1474a

Version 2.0

  • Robo:Bit v2.0
  • Battery Holder with no wires, mounted on a PCB
  • Yellow gear motors x 2 with JST connectors
  • 1 caster (plastic ball plus plastic housing)
  • 25mm brass female-female pillars x 2
  • 11mm brass female-female pillars x 2
  • 20mm brass female-female pillar (M2.5) x 2
  • 30mm brass female-female pillar (M3) with holes x 2
  • 6mm M3 screws x 2
  • 30mm M2.5 screws x 4
  • 6mm M2.5 screws (pan head) x 6
  • 8mm M2.5 screws (CSK) x 2

 

step01

Version 1.1

  • Robo:Bit v1.1
  • Battery Holder
  • Yellow gear motors x 2
  • 1 caster (plastic ball plus plastic housing)
  • 10mm black nylon male-female pillars x 2
  • 15mm black nylon female-female pillars x 2
  • 20mm brass female-female pillar (M2.5) x 2
  • 30mm brass female-female pillar (M3) with fitted attachments x 2
  • 11mm brass female-female pillars x 2
  • 25mm M3 screws x 4
  • 6mm M2.5 screws (pan head) x 6
  • 8mm M2.5 screws (CSK) x 2
  • 4-cell AA battery holder

 

Version 1.0

  • Robo:Bit v1.0
  • Battery Holder
  • Yellow gear motors x 2
  • 1 caster (metal ball plus plastic housing)
  • 10mm black nylon male-female pillars x 2
  • 15mm black nylon female-female pillars x 2
  • 25mm black nylon female-female pillar (M3)
  • 25mm brass female-female pillar (M3) with fitted attachments
  • 11mm brass female-female pillars x 2
  • 25mm M3 screws x 4
  • 6mm M2.5 screws (pan head) x 8 (or x10 – see step 6)
  • 8mm M2.5 screws (CSK) x 6 (or x4 – see step 6)
  • M2.5 nuts x 4
  • 4-cell AA battery holder

 

For v1.0 assembly, go to Step 2A

For v1.1 assembly, go to Step 2B

Step 2 (v2) Make the Motor Assembly v2

IMG_1475a

You will need the two 30mm brass pillars with holes, two 20mm brass pillars and 4 long (30mm) M2.5 screws

IMG_1476a

Push two of the screws through the holes in one of the motors and through the holes in the 30mm pillar as shown. Take care that the axle of the motor is on the outside and the pillar is on the inside. Also ensure that the motor wires do not get trapped under the pillar.

IMG_1477a

Screw the 20mm pillars on tightly as shown above.

IMG_1478a

Then fit the remaining 2 long screws through the second motor, ensuring the orientation is correct as shown above

IMG_1479a

Finally, screw the second motor firmly to the 20mm pillars. You have now completed the motor mount assembly. Now skip to Step 3

Step 2B (v1.1). Make the Motor Assembly v1.1

STP51

You will need the 2 brass bracket assemblies, 20mm female-female pillars (x2) and 30mm M2.5 screws (x4)

STP52

Push the 30mm screws through the motors as shown, with the screw threads protruding through the side with wires

STP53

Slide the bracket assemblies onto the ends of the 30mm screws as shown above. Ensure that:
1. The vertical 30mm pillar is away from where the wires exit the front of the motor
2. The wires go over the vertical pillars, not under them
3. The short spacers stick out on one side – this is the side that fits against the motor – do not try to fit them the other way around

STP54

Screw the two 20mm female-female brass pillars onto one motor as shown above

STP55

Finally, add the second motor and screw tightly together

 

Step 3. Prepare the Robo:Bit for Fitting

STP56

You will need the Robo:Bot circuit board, 6mm M2.5 screws (x2) and 11mm pillars (x2)

STP57

Fit the pillars in the positions shown above and screw tightly together

 

Step 4: Fit the Robo:Bit to the Motor Assembly

STP58

You will need the motor assembly from Step2, the Robo:Bit assembly from Step3 and M3 6mm screws (x2)

STP59

Pass the M3 6mm screws through the Robo:Bit board and into the top of the pillars in the brass bracket assemblies as shown above

STP60

Plug the two cables in making sure the left motor is plugged into the left socket and the right motor is plugged into the right socket

STP61

The photo above shows the gap between the motors and the Robo:Bit board

Now skip to Step 5

 

 

Step 2A. Make the Motor Assembly v1.0

step03

Place the motors into position as shown above, with the axles facing outwards

Use 2 of the 25mm screws to fit the M3 black nylon 25mm female-female spacer to the bottom holes in the motor

Use the other 2 of the 25mm screws to fit the brass bracket assembly to the top holes, making sure that the connector parts point upwards as shown above

 

Step 3A. Prepare the Robo:Bit for Fitting

step04

Fit 4 of the 8mm M2.5 CSK screws and the 4 nuts to the Robo:Bit as shown above. Pass each screw from the top of the board into a nut on the bottom. Tighten securely.

step06

Using 2 of the 6mm M2.5 pan head screws, fit the 11mm brass pillars in place for the 4-cell battery holder – the outermost two holes – as shown above. Tighten securely

 

Step 4A: Fit the Robo:Bit to the Motor Assembly

step07

Use 2 of the 6mm M2.5 pan-head screws to attach the Robo:Bit to the upwards-facing connectors on the brass bracket assembly as shown above. Tighten securely.

Push the JST plugs from the motors into the sockets underneath the Robo:Bit controller. The wires are short enough to stay tidy.

 

Step 5. Fit the Front Caster

step09

For v1.0 and v1.1, Screw each 10mm black nylon male-female pillar into a 15mm making it into a 25mm female-female pillar.

For v2, use the 25mm brass female-female pillars

Use a 6mm M2.5 pan-head screw to fit each pillar to the front holes on the Robo:Bit

step10

Then use two more 6mm M2.5 pan-head screws to fit the caster housing to the pillars (you will have to remove the metal ball while you do this)

 

Move to Step 6A for v1.0 and v1.1

Step 6 (v2): Fit the Battery Holder

IMG_1492a

You will need the battery holder assembly and the two 8mm countersunk screws

IMG_1493a

Screw the battery holder assembly tightly to the upright pillars, ensuring that the labelling is at the rear of the Robo:Bit as shown above. There is no need for wires as the battery power passes directly through the upright pillars.

 

Step 6A (v1.0 and v1.1): Fit the Battery Holder

step11

Screw the wires into the power terminal. Red to 5V and Black to GND. Wrap the wires tidily out of the way under the battery holder

step12

Use the remaining 2 of the 8mm M2.5 CSK (or 6mm pan head) screws to screw the battery holder to the brass mounting pillars. With some battery holders, the wide countersunk screws don’t fit, so swap them with the 2 smaller pan-head screws used to hold the mounting pillars for the front caster

 

Step 7. Finish off and Go!

step17v1.0 or v1.1 Ultrasonic

Push on the wheels. Be careful to hold the motor as the wheels can be quite stiff to fit, especially the first time

Push in or bolt on the Ultrasonic Sensor (if you have one)

IMG_1498av2 Ultrasonic

Push the BBC Micro:Bit into the edge connector (LED display and buttons upwards)

Program -> Switch On -> Go!

 

Fitting the Line Sensors

Step 8. Check you Have the Parts

step22

  • 30mm black nylon M3 pillars
  • 6mm M3 screws x 4
  • Line follower sensors x 2
  • 10cm GVS cables x 2

 

Step 9. Fit the pillars to the Robo:Bit

step24

Use 2 of the 6mm M3 screws to fit a 30mm black nylon pillar to each front corner of the Robo:Bit board

 

Step 10. Fit the Sensors

step26

Push one of the GVS leads onto each line follower sensor. Make sure you use the colour coding: Brown for Ground (G), Red for volts (V+) and Orange for Signal (S)

Then use the remaining 2 of the 6mm M3 screws to to fit the line sensors to the bottom of each pillar. Use the hole near the centre of the sensor, not the one at the front. The wires should be at the back, as shown above

 

Step 11. Plug the GVS leads into the Connector

step28

Pass the wires around the motor supports and then into the 3×2 male header underneath the Robo:Bit board. Make sure brown goes to Ground (GND), Red to power (3V) and Orange to Signal (SIG)

Also make sure you connect the left one to the left set of pins, and the right one to the right set of pins. It is VERY confusing when writing programs with these reversed (trust me, I know this)

 

Step 12. Trim the Sensors

Each sensor has a little preset potentiometer (pot) which can be turned to define the position at which it detects a line.

Turn the pot until the red LED on the sensor _just_ turns off. It is then at its most sensitive.

When using 3V, these sensors are not as sensitive. With a little ingenuity (and a different cable) you can connect the power line to VCC (the bottom 3 pins on the 8×3 header on the top of the board). This will make the sensors more sensitive.

 

 

Bit:Bot Robot for BBC Micro:Bit

Bit:Bot – The Integrated Robot for BBC Micro:Bit

bb01

Purchase BitBot here

 

A great way to engage young and old kids alike with the BBC micro:bit and all the languages available. Both block-based and text-based languages can support the Bit:Bot

You can also use the Radio or Bluetooth functionality of the Micro:Bit to send and receive commands and date. See a Bluetooth tutorial here

Warning: On versions before v1.2, the line follower sensors share the same pins as the buttons. Depending what language you are using, when the Micro:Bit is started or reset it will check the 2 buttons and start pairing if they are both pressed. With the Bit:Bot, this translates to both line follower sensors getting reflections. You can stop it happening by lifting it off the surface before switching on. On v1.2 the line sensors are disabled for 2 seconds after power on so that the MicroBit doesn’t detect the pairing situation. In addition there is a small switch that allows you to disable the line follower sensors completely, allowing the use of the MicroBit buttons.

 

Features

The Bit:Bot gives you all these features:

  • 2 micro-metal gear motors. Both fully controllable in software, for both speed (0 to 100%) and direction (forward or reverse)
  • Wheels with rubber tyres for maximum grip
  • 12 mini neopixels in 2 sets of 6 along the arms either side. Select any colour for any pixel, produce stunning lighting effects as your Bit:Bot moves around
  • 2 digital line following sensors. Code your own line-following robots and race them to see whose code produces the fastest lap time!
  • 2 analog light sensors (front left and front right) so your Bit:Bot can be programmed to follow a light source such as a torch, or you could code it to go and hide in the darkest place it can find
  • Buzzer, so you can make beeping sounds whenever you want
  • Powered from integrated 3xAA battery holder with on/off switch and blue indicator LED
  • Easily plug your BBC micro:bit in and out using the edge connector
  • Extension port for additional neopixels (such as McRoboFace)
  • Expansion connections at the front for additional sensors (eg. ultrasonic distance sensor, Talon grabber)

 

Assembling

Step 0 – Check you have all the correct parts:

  • 1 caster assembly (either metal ball or plastic ball)
  • 2 x 6mm M2 pan head screws (now already fitted)
  • 2 x M2 nuts (now already fitted)
  • 2 x 12mm brass pillars
  • 4 x 8mm M2.5 countersunk screws
  1. Use the M2 6mm (panhead) screws and nuts to attach the front caster housing, then push the caster ball into the housing
  2. Use the M2.5 6mm panhead and 8mm countersunk screws to fit the battery pack onto the 2 metal pillars: ENSURE the on/off switch is at the rear of the Bit:Bot
  3. Push the wheels on with the smooth side outwards. The axle should come flush with the outside of the wheel and not protrude (or the inside can catch on the motor housing)
  4. Push your BBC micro:bit into the edge connector with the LEDs and switches on the top

Click on any image to enlarge

Step 1 – Fit the Front Caster (already fitted to current models)

Step1

Step2

Step3

Step4

Step5

 

Step 2 – Fit the Battery Holder

At this point you should have 4 screws left. Either 4 x 8mm countersink, or 2 x 6mm panhead and 2 x 8mm countersink.

If you have the 6mm panhead screws, use these to fit the 12mm brass pillars to the Bit:Bot main PCB.

Always use 8mm countersink screws to fit the battery holder to the brass pillars.

Step6

Use either 6mm panhead or 8mm countersink to fit the 12mm brass pillars to the main board (above)

 

Step7

Use the 8mm countersink screws to fit the battery holder to the brass pillars.

 

Step 3 – Fit the Wheels

Step8

Push the wheels on, so that the axle is flush with the outside of the wheel

 

Step 4 – Attach your BBC micro:bit

Step9

 

Know Your Bit:Bot

Above

bb17a

This shows the neopixels (6 on each arm), the 2 light sensors, on/off switch and indicator LED

The buzzer is below the on/off switch and the edge-connector is below the front of the battery holder

 

Below

bb15a

Now you can see the 2 line sensors and the port for neopixel extensions and general purpose expansion connector. Connection labelling is on the underside

 

Programming in Microsoft Makecode

For Makecode block programming, you can use the official BitBot extension. Go to the Advanced tab (or press the cog icon) and select Extensions. Then search for BitBot and select the official package. This will give you a BitBot tab in the toolbar with 4 sub-categories for the Motors, Sensors, LEDs and advanced (…more).

For text-based programming there is micro-python, and I prefer to use this offline using the Mu editor.  It provides a very neat and easy way of interfacing to the micro:bit without all the fuss of dragging and dropping. NOTE: At the time of writing (December 2016), there are problems with Mu when using PWM with neopixels and other things, so it best to use the online micropython editor for now.

The following examples use both of these languages to show code fragments.

Note on examples: We want to show people how the various features can be used. We don’t want to do the coding for you – that is the learning experience you should be taking away from using it. In the following examples, we will give you the tools to use all the features of Bit:Bot but it is up to you to combine them together in your code to make it do something useful. We do give a complete example of line-following – but it is a very basic algorithm and will get confused at T-junctions  and crossings; and it doesn’t use the neopixels.

Download Python examples at the bottom of this page.

Some great tutorials/examples by Mark Atkinson here

Motors

Under the Motors tab there are 5 blocks available as shown:

The first one “drive at speed 600” simply turns both motors at the speed selected between 1023 and -1023. 1023 is full speed forwards and -1023 is full speed backwards. Setting the speed to 0 will stop both motors.

The second one will do the same, but then stop both motors after the time selected.

The next two “spin <left> at speed 600” will spin the BitBot on the spot by turning one wheel at the selected speed forwards and the other at the selected speed backwards.

The final block allows you to control the individual motors. Either the left motor or the right motor (or both). This is so that you can make a long sweeping turn instead of spinning on the spot, by making one motor go slower than the other.

LEDs

A great feature of the Bit:Bot is the set of neopixel LEDs, 6 down each arm.

The Makeblock extension supports these easily

The LEDs category has the basic blocks as shown above, but there are additional advanced blocks in the “…more” category

Normally, the process to update LEDs is a 2-stage process:
1. Make the changes to the LED colours (eg. “set all LEDs to Red”)
2. Send all the changes to the LEDs (“show LED changes”)

However, we have made it so that the default is “automatic updates”, so any changes made to the LED values will automatically result in the LEDs changing. This is a slower way to do things, but much easier to understand. If you want the normal, manual, update method then this can be selected from the “…more” category.

You can get a simple rainbow pattern on all the LEDs with just the “set led rainbow” block

And by using the forever block you can get the LEDs to animate using “rotate LEDs” and a pause to slow them down.

Sensors

The Sensors category provides access to both the integrated features (buzzer, line follower sensors, light sensors) and the optional addons (ultrasonic distance sensor, Talon grabber)

Buzzer

The “turn buzzer on/off” block enables you to make a simple beep

The program above will make a very annoying beep, beep, beep sound forever…

Ultrasonic Distance Sensor (sonar)

The “read sonar as cm/inches/microseconds” block enables you to read the distance from the front of the Bit:Bot to the nearest obstacle. Don’t expect this to be stunningly accurate, but it is good enough for obstacle avoiding etc. Here is a very simple obstacle avoiding program

In this program it reads the distance in centimetres. If it is nearer than 20cm then it reverses and turns, otherwise it carries straight on.

Line Following Sensors

The idea of these sensors is that you create a black, non-reflective, line on an otherwise reflective surface. You can then program the Bit:Bot to follow the line.

The best way to get a good line is to print a track on a laser printer. We use these printable tiles which are excellent

This is a very simple and very inefficient line follower program. But it works. If the left line sensor detects a line then spin left, if the right line sensor detects a line then spin right. Otherwise carry straight on. You can add some LEDs to the program to make it more interesting. Here we have a Red LED on the end of each stalk if it is turning that way, or 2 Green LEDs if it is going straight

 

Programming in Python

For text-based programming there is micro-python, and I prefer to use this offline using the Mu editor.  It provides a very neat and easy way of interfacing to the micro:bit without all the fuss of dragging and dropping.

Note on examples: We want to show people how the various features can be used. We don’t want to do the coding for you – that is the learning experience you should be taking away from using it. In the following examples, we will give you the tools to use all the features of Bit:Bot but it is up to you to combine them together in your code to make it do something useful. We do give a complete example of line-following – but it is a very basic algorithm and will get confused at T-junctions  and crossings; and it doesn’t use the neopixels.

Download Python examples at the bottom of this page.

Some great tutorials/examples by Mark Atkinson here

Motors

Each motor has two pins connected to it. One determines the speed and the other the direction:

Left motor: Speed Pin 0, Direction, Pin 8

Right motor: Speed Pin 1, Direction Pin 12

The simplest way to make the motors move is to set the Speed pin to HIGH and the Direction pin to LOW (to move full speed forwards)

Move left motor Forwards:

pin0.write_digital(1)
pin8.write_digital(0)

Move left motor Reverse:

pin0.write_digital(0)
pin8.write_digital(1)

If we want to change the speed of a motor, so that it is not going at full speed all the time, we need to use PWM (Pulse Width Modulation). This is means of changing the amount of power given to the motor by switching it on and off very fast. The percentage value of PWM determines the amount of each cycle that the output is ON. So a percentage of 100% is the same as being on all the time and thus the same as the examples above. A percentage of 50% would mean that the motor is only energised half the time, so it will go much slower. Note that the actual speed of the motor is not the same as the percentage of PWM – the motor won’t turn at all if the PWM value is too low and you will also get some stuttering at certain values. Nevertheless, being able to change the speed makes for a much better robot. For example, you can make a line follower that smoothly follows the line, rather than the normal shaking left and right.

To change the PWM value of a pin, we must use the analog_write commands. These can be set to a value between 0 (always off) to 1023 (always on), so 50% would be 511. Here are the commands to change the speed of the Right motor to approx 75% (value is 770)

Move right motor forwards at 75%

pin1.write_analog(770)
pin12.write_digital(0)

Doing this for the motors moving in reverse is a little confusing. Remember we need to change the direction pin to 1 for reverse. Then we need to set the amount of time in each cycle that the speed pin is LOW. This is the opposite of moving forwards, where we set the time for it to be High. Se we simply take the number (770 in this case) away from 1023, giving 253:

Move right motor Reverse at 75%

pin1.write_analog(253)
pin12.write_digital(1)

 

Neopixels

In fact, the name “neopixel” is a termed coined by Adafruit, but like “hoover” was a name of a brand of vacuum cleaner and is now a general term for all similar products, whoever makes it. The generic term is “smart RGB pixel” and is usually referenced with the name of the chip WS2812B. However, there are many different chips, all performing in a compatible way. The ones on the Bit:Bot are actually SK6812-3535

These smart RGB pixels are able to display any of 16 million colours by selecting a value of 0 to 255 for each of the Red, Green and Blue LEDs on each chip. The whole thing is controlled by a single pin on the BBC micro:bit (pin 13 for Bit:Bot). It is simple to use the included neopixel libraries to control each pixel individually.

The pixels are labelled on the Bit:Bot. From 0 to 5 on the left arm and from 6 to 11 on the right arm. If you connect any more neopixels into the extension port, then the new ones will start at 12.

Set neopixel 2 to purple (red and blue)

import neopixel
np = neopixel.NeoPixel(pin13, 12)
np[2] = (40, 0, 40)
np.show( )

The first line imports the neopixel library. We only need to do this once, at the very top of your Python programThe second line creates an Python list with an element for each pixel. As shown, it specifies 12 pixels connected to pin 13. If you added more neopixels then you would increase the number from 12 by the number of pixels you added. eg. if you added a McRoboFace, then the total would be 12 + 17 = 29 so you would change the line to: np = neopixel.NeoPixel(pin13, 29)
The third line sets the pixel we have selected (number 2 in this case) to the colour which is set by three values in the brackets, each value can be from 0 to 255 and covers Red, Green and Blue. In our example we have set Red and Blue to 40.
The fourth line tells the neopixel library to copy all the data to the neopixels, from the Python list that we have been working with. It is only at this point that the LEDs change. In general, you would make all the changes you want and only at the end would you use a np.show( )

Line Follower Sensors

NB. Version 1.0.0 of mu editor (v1.0.0) incorporates an updated version of micropython that allows these pins to ONLY be used as buttons. So instead of using pin11.read_digital() you need to say button_B.is_pressed() for instance. The examples will be changed to reflect this

These are digital inputs and connected to Pin 11 (left) and Pin 5 (right). These are the same pins as used by the buttons, so pressing a button will have the same effect as detecting a black line. This may have unexpected side-effects – as switching the micro:bit on when both buttons are pressed can cause it to enter Bluetooth pairing mode (depending what software is installed).

So you can use the normal Button inputs to read the sensors if you want, or you can use digital_read commands (as shown below). If the left sensor detects a line, it means the Bit:Bot is too far to the right, so it should move left. The opposite is the case if the right sensor detects a line. Here is some simple code for line following in Python (the actual motor commands are in separate functions for clarity)

while True:
    lline = pin11.read_digital()
    rline = pin5.read_digital()
    if (lline == 1):
        spinLeft( )
    elif (rline == 1):
        spinRight( )
    else:
        forward(speed)

Light Sensors

These are analog sensors and will give a value of 0 to 1023, where 0 is fully dark and 1023 is maximum brightness. As there are only 3 analog pins available on the micro:bit (without affecting the LED displays) and we are using 2 of them to control the motors, we only have one left (Pin 2) to read the analog values from 2 line sensors. How can we do this? Well, the Bit:Bot has an analog switch that uses a digital output signal (pin 16) to determine whether the analog input we are reading is for the left sensor or the right sensor.

Therefore, to read the light sensors we need to set the selection output pin first, then read the analog data.

In Python, we can do it like this to read the values into 2 variables called leftVal and rightVal:

Pin16.write_digital(0) # select left sensor
leftVal = Pin2.read_analog()
Pin16.write_digital(1) # select right sensor
rightVal = Pin2.read_analog()

 

Buzzer

The buzzer is a very simply device that outputs a 2.4kHz sound when it is set to ON. It is NOT controlled by the tone signal that can be output by the micro:bit on Pin 0 so you don’t need to install any libraries to operate it.

It is connected to Pin14. Setting this to ON (1) will activate the buzzer and setting to OFF (0) will deactivate it.

In Python, a very simple and annoying beep, beep, beep sound can be made as follows:

while True:
    pin14.write_digital(1)
    sleep(400)
    pin14.write_digital(0)
    sleep(400)

Ultrasonic Distance Sensor

This optional HC-SR04 ultrasonic distance sensor addon can be used most easily in Microsoft PXT. In MicroPython we can use the utime module to measure time at microsecond level. Below we have a function called sonar() which returns the number of cm to the nearest object. Then we have a while loop that prints the distance every second:

from microbit import *
from utime import ticks_us, sleep_us

def sonar( ):
    SONAR.write_digital(1) # Send 10us Ping pulse
    sleep_us(10)
    SONAR.write_digital(0)
    SONAR.set_pull(SONAR, NO_PULL)
while SONAR.read_digital() == 0: # ensure Ping pulse has cleared

        pass
    start = ticks_us() # define starting time
    while SONAR.read_digital() == 1: # wait for Echo pulse to return
        pass
    end = ticks_us() # define ending time
    echo = end-start
    distance = int(0.01715 * echo) # Calculate cm distance
    return distance

while True:
    display.scroll(sonar())
   sleep(1000)

Example Micropython Programs

 

 

Playground for Crumble, Micro:Bit & Raspberry Pi

Playground for Crumble, BBC Micro:Bit and Raspberry Pi

IMG_0999b PlayMicro03aPlayCrum_03

(Click on any image to enlarge)

 Purchase Here

Playground Overview

The Playground system allows you to connect external electronics (inputs, outputs, sensors, etc.) to your controller. Currently supports Crumble (from Redfern Electronics), Raspberry Pi and the BBC micro:bit.

The connections from the controller are converted to 3-pin 3.5mm jack connections and the connecting cables are 20cm jack cables – although longer cables can be used if required.

The separate electronic parts, Gizmos, can be used with any Playground. The exception being the Motor Gizmo, which can only be used with Crumble, as the micro:bit does not have integral motor drivers.

All of the Gizmos can be used within your programs using the built-in drivers for the relevant part.

Because each connection includes the necessary power and ground, you don’t need to wire these in separately – this transforms what can be a complicated and messy wiring setup into something tidy and more easily understood

Please check out these videos for Playground for Crumble and Playground for MicroBit

 

Installing Raspberry Pi Software

We have created a python library module that allows you to use the Playground for Raspberry Pi easily and quickly. You can install this from your Raspberry Pi connected to the internet as follows.

  • Download the latest version of the software using wget like this from a command line (eg. LXTerminal):
    wget http://4tronix.co.uk/pg.sh -O pg.sh
    bash pg.sh
  • This will create a new folder on your Pi in the /home/pi folder called playground (all lower case) with the playground.py library module and example files

 

Gizmos

IMG_0337a

Initially, we have 11 Gizmos for sale. These have been colour-coded in a similar way to our Crumbs:

  • Blue:  Digital inputs, such as a Button or Touch sensor
  • Yellow:  Analog inputs, such as a Light sensor or Dial
  • Black: Digital outputs, such as LEDs or Buzzer
  • Red:  Analog outputs such as the Servo or Motor
  • White:  Smart Pixels (aka “neopixels” or “sparkles”), individually addressable, chainable, RGB pixels (Flame, Blaze and Fire Stick)

 

Button Gizmo

Button_02

This provides a simple digital input to Playground. It is Active (High) when pressed and inactive (Low) when not pressed. There is a white indicator LED to show whether it is active or not.

Worksheet Links: Crumble  BBC micro:bit   Raspberry Pi

 

Touch Sensor Gizmo

Touch_02

This provides a digital input to PlayGround. Simply touch the pad on the sensor for it to become active (High) and release for it become inactive (Low). There is a white indicator LED to show whether it is active or not. In fact the sensor will detect your finger without actually touching, so you can do experiments to see how many sheets of paper you can cover it with before it stops working

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Dial Gizmo

Dial_02

The Dial Gizmo provides an analog input to your Playground. On the Crumble it will read from 0 to 256, while on the micro:bit it will go from 0 to 1023. The actual top end number will vary due to various losses in the system

Worksheet Links: Crumble  BBC micro:bit    Raspberry Pi

 

Light Sensor Gizmo

Light_02

The Light Sensor Gizmo is an anlog input Gizmo that reacts to the brightness of light to the sensor in the centre. It is tuned to be sensitive to daylight. The values vary from 0 (dark) to 256 (bright) on the Crumble, while on the micro:bit it will go from 0 to 1023. The actual top end number will vary due to various losses in the system

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Traffic Light Gizmo

Traffic_02

The Traffic Light Gizmo is a digital output Gizmo for your Playground. Each of the large 10mm LEDs will turn on when the appropriate input is set to High. There are three inputs, one for each of Red, Amber and Yellow

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Buzzer Gizmo

Buzzer_02

The Buzzer Gizmo is a digital output Gizmo for your Playground. When the input is set to High, the buzzer will sound and a white indicator LED will light

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Flame Gizmo

Flame_01

The Flame Gizmo provides a single, fully controllable, RGB pixel. This allows you to change the colour to any one of 16 million different colours. These are chainable, with both an input and an output connector. On the Crumble, these “smart pixels” are referred to as “Sparkles”, while on the micro:bit they are known as “neopixels”

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Blaze Gizmo

Blaze_02

The Blaze Gizmo gives you a ring of 8 , independently controllable, RGB pixels. This allows you to change the colour of any or all of them to any one of 16 million different colours. On the Crumble, these “smart pixels” are referred to as “Sparkles”, while on the micro:bit they are known as “neopixels”. These can be added onto the end of a chain of Flame Gizmos if required, or used on their own

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Servo Gizmo

Servo_02

As the name suggests, this Gizmo allows you to very easily connect a miniature 9g servo to your Playground. Plug it in, then program it for a 180 degree range of movement. With the Crumble, the allowable range is -90 to +90. Do not try and use it outside the allowable range.

Worksheet Links: Crumble  BBC micro:bit  Raspberry Pi

 

Motor Gizmo

(Not compatible with micro:bit Playground)

Motor_01

The Motor Gizmo is driven directly from the Crumble motor driver outputs – it cannot work with the micro:bit. Use the Crumble motor control blocks to set the speed and direction of up to 2 Motor Gizmos. You can build yourself a robot very easily with 2 of these

Worksheet Links: Crumble  (BBC micro:bit and Raspberry Pi not available – a prototype motor Gizmo for Pi is shown at top of page – this has a built in motor driver.)

 

Prototyping Gizmo

Proto_01

This simple Gizmo allows you to build your own Gizmo for those inputs or outputs that are not yet available as a ready-made Gizmo. For instance, you could make a temperature sensor, or have a controllable relay. The board has 4 holes for the Signal, 6 for each of Power and Ground, and 48 for you to use for your creation.