Some tips on using the Smart 2 Wheel Arduino Robot chassis

I'm a big fan of these basic 2 wheel chassis.  They're cheap to buy.  I've seen them on eBay for less than £6.00 without the batter holder.  There is enough space on them an Arduino or PiZero with a motor controller alongside the battery pack.

2 wheel smart robot chassis

They're usually listed as "2 Wheel Smart Robot" with the word Arduino added in there somewhere even thought they are not Arduino specific.  I think it's there to improve SEO for all the people making their first robot using an Arduinio.  Also, they are not smart, there is no intelligence provided.  They usually come with  tachometer encoders for the wheels, but you need extra electronics to read them.

I've used these chassis a few times and these are some gotchas that I'd to figure out.

1. The perspex is clear
If the perspex is opaque or brown in colour then this is a layer that can be pealed off.  It's there to protect the perspex.  You can leave it on but it's supposed to come off.

2.  The caster goes to the back.
Even though most of the pictures you see show the caster wheel at the front this is really a drag wheel and should be at the back of the bot.
The fact the caster spins means if it is put at the front then you're pushing against the caster when turning.  It's like having a wobbly shopping trolley.  Easier to pull behind you than push in front. Also, you can see from the image the (correct) front has more mounting options for sensors which makes sense.

3.  The battery box can be screwed on the underside
All pictures I've seen always have the AA battery box on the top.  Makes sense as gravity will keep the batteries in.  But, if needed the battery box can be screwed to the underside of the deck giving more real estate on the top for other components.

4.  The connections on the motors are very fragile
Where you solder the wires to the motors is very fragile and prone to snapping off if put under any strain.  So, it's best to put in place some strain relief.
The easiest and without needing any additional hardware is to knot the two wires around the plastic fastener holding the motor in place.  In this way if someone pulls on a wire or it gets snagged it doesn't put any pressure on the actual connection on the motor.

Strain relief on the motor wiring

Some final thoughts

I've used these motors with L298N as well as L9110s motor controllers.  Both work great.  The L298N is bigger and really over specced for these little motors so the L9110s is more than capable of driving them.
The cheap L9110s board only has one GND connection and assuming using a different power supply for the motors and the controller (Pi/Arduino) you'll need to tie the GND from the different power supplies, the controller and the L9110s together.  I usually use one of the additional GND pins on the controller.  Arduino Uno has three GND pins, the Arduino Nano has 2 and the Raspberry Pi has 8.

L9110s - only one GND connection

I've heard reports that as the gears are plastic they can be shredded.  A lot of fast reversing with a decent power supply can put the cogs under a lot of strain.  This is one of the main compromises for the price.  So, either limit the speed at which the motors can change direction or be ready to replace the motors.

These little yellow motors look like they're all the same, but the gearing inside them can be different.  If you do need a replacement motor you may not get the same gearing ratio which would affect the ability of your robot to go in a straight line or just move consistently.

Even with all this I think these kits are a great start.  They're easy to put together.  Reliable (enough), powerful (enough) and cheap so a great place to start.
Add an Arduino Nano and an L9110s with a small breadboard to connect everything together and you have a capable platform to develop from for less than £10.00.
You can then add ultra-sonic sensors, line following sensors, infra-red remote control, Bluetooth interface, or even the tachometers to measure speed and lots more...
Giving an easy and cost effective introduction to robots.
This may not be the chassis you finish with but it's definitely a good place to start.
And if you're already thinking of upgrades there is a 4 wheeled version as well for not much more.

4 Wheel Smart Chassis

Happy roboting.

Electronics Maker Christmas stocking fillers list

It's that time of year when my family ask me for ideas of presents for Christmas and my Birthday.  (both December)

With electronics bits being a bit specific/esoteric I stopped trusting that if I said what I wanted they would get me the right thing after I gave my wife a link without a description for a new CPU.
By the time she clicked it the link redirected to a few screws.  Luckily she checked before buying and I was able to get her the alternative link.

So, these day I provide a wish list email with more items than I expect to get so I still have the surprise when I open the packaging as to what they give me.

This year I've decided to share the list.  This list may be added to as I think of more things.
Before you ask things like Arduinos, Raspberry Pis, Circuit Playground boards are not on this list as these are things I have usually already got a stash of.  This list is for the other bits that make those things useful.  The kind of things it would be useful to have before starting a project but may not have already or may have run out of.

I try to keep the items to less than £20 so for many these are good stocking fillers.


USB Current Tester - £4.50

I buy random items off the Internet and for batteries and USB PSUs I want a way to see if they meet their stated ratings.

Heat Resist Soldering Mat - £9.90 - £15.00 - There are bigger and smaller ones out there as well.
I have a regular A3 cutting mat but like this because of the different compartments to keep bits as I regularly drop screws and tools and hope this will help me be more organised when working on something.

Crimping Tool with 450Pcs Connector - £23.99  

I sometimes use buttons with spade connectors and at the moment I solder the wires on which is not ideal.  Want to start using the correct connectors for the correct job and not just bodge something that later causes a headache that I have to fix.

Anker 4-Port USB 3.0 Hub  - £10.99  
Sometimes for the Raspberry Pi I need to burn multiple SD cards.  The great Etcher will burn multiple images at the same time so with this I can add 3 more to be burned in parallel (it's not 4 as I lose a port to connect it)

Adafruit Hook-up Wire Spool Set - 22AWG Stranded-Core - £17.93 

Starting to try and be more organised so like the idea of this set of wires.  I have loose spools of wire around the place so the plan is to replenish the spools when they run out.

20pcs Multicolored Dupont Wire 40pin Male to Female, 40pin Male to Male, 40pin Female to Female Breadboard Jumper Wires  - £5.95

Saying that I still do breadboard stuff so it's always good to replenish the stock of Dupont jumper wires.

2.54mm 2x20 40-Pin Female Pin Header Socket Connector Strip 10 Pcs - £1.94

Having recently committed a project to an actual prototyping board rather than using a breadboard I want to do more of that for my Raspberry Pi projects so need a bunch of 2x20 female connectors to hand.  Last one I used I 'borrowed' form a Kickstarter I backed, so that's now an incomplete kit.

SanDisk Ultra 16GB microSDHC Memory Card + SD Adapter - £5.99

I'm always looking for microSD cards, so every year I add them to the stocking filler list.

They're small and I'm clumsy so replenishing stock is an ongoing activity. 

Shakey Shakey - a game using title switches

For the most recent Egham Raspberry Jam @EghamJam we did two workshops.
One was NoPi Blinky, making LEDs blink without any programming. More to come on this as during the workshop we found a few typos.

The other was Shakey Shakey.

For the workshops my goal is to do something slightly different that not only teaches the attendees something new from either a programming or electronics standpoint but also shows them creative options.

Shakey Shakey was based around really simple tilt switches.  They're basically a small tube with a contact inside that moves as you tilt the tube.  Really simple and really cheap. On eBay UK they're about £1.50 for 20. So, ideal when you need a bunch for the Jam

The only other things needed then were some female-female jumper wires and some 2 core wire.
I cut the female-female wires in 2 giving me a pair of wires that had the female connectors on one end and bare wire the other.  Cut the 2 core wire into about 150cm lengths and used them to connect the switch to the other wires giving a nice long wire for the kids to shake without (hopefully) unplugging the wires or pulling on the Raspberry Pi.

With the hardware sorted I them did the worksheet which is available to download from GitHub along with other Jam worksheets.

Shakey Shakey worksheet

The worksheet goes through:

• Connecting a tilt switch
• Python code to read the switch and display how many times it connects
• Adding a pause to deal with debouncing
• Adding a second tilt switch
• Updating the code so the switches have to be activated alternatively
• Final update of the code to add a timeline making it into a game

We had a full workshop and the kids who took parts seemed to really enjoy the coding and then playing the new game they created.

At the end I challenged the participants to come back to the next Egham Raspberry Jam (21st October 2018) with their own program that uses the same tilt switch controllers.  The worksheet at the end gives some suggestions.  Here's looking forward to the 21st of October to see what fantastic creative ideas the kids come up with.

Cat or Dino- Scratch 2.0 game

I saw a tweet from the @Raspberry_Pi Foundation about a game called Knifey Spoony by @Jonic one of their senior web developers did using pico-8.

Our Senior Web Developer @Jonic just released a game called Knifey Spoony.
Playing Knifey Spoony will be all you do today.
Knifey Spoony is your life now.
Life is Knifey Spoony.
Knifey Spoony.
🔪🥄 https://t.co/wTOvwkeU92

— Raspberry Pi (@Raspberry_Pi) June 18, 2018

The idea of the game is to select if the image is a spoon or a knife as quickly as you can with a timer running getting faster and faster the higher your score, so the pressure is on.

I thought this could be done with Scratch, so I fired up Scratch 2.0 and had a go.

Here is the result.  It uses only built in graphics making it easy for anyone to replicate and extend.

It is done with Scratch 2.0 but there is nothing special so it should work with Scratch 1.4 on the Raspberry Pi as well.

https://scratch.mit.edu/projects/229582133

PiGPIOPin - when you want to use pin numbers and not BCM on the Raspberry Pi in Python

A while back I was doing some bare Arduino compatible boards using the ATMega328 chip. From this I saw that Arduino did not map the pins on the IC to the same numbers on the Arduino.  They used a simple order on the Arduino board and the Arduino ID so it was easy to find the right pin for wiring and also for your code.

Only problem is when you use the chip with the bootloader the mappings are different to the pin number so you need a lookup tool to know when you want to use Arduino Pin 13 that it's ATMega Pin 19.
After a while this became a bit annoying so I put together an .h file with a bunch of constants that got around this.

http://www.winkleink.com/2014/01/arduinopinsh-converts-atmega328-pins.html

On the Raspberry Pi there is a similar situation.  The default numbering mechanism used is the BCM numbering which is great if you're operating at chip level, but at a board level it means things like:

BCM GPIO 5 is board pin 29

I still have to count pins to get to board pin 29, so having to also know it's then GPIO 5 in my code can sometimes be a bit annoying.

The original RPi.GPIO library allows you to choose BCM or Board numbers

 import RPi.GPIO as GPIO  

GPIO.setmode("GPIO.BCM")
or
GPIO.mode("GPIO.BOARD")

Giving the user the choice.

With the fantastic GPIOZero BCM numbering is enforced and there is no option to use board numbering.
GPIOZero is a great library and makes controlling motors, working with MCP3008 (analog input) and distance sensors a lot easier.

For those who want to use board pin numbers and want to take advantage of GPIOZero the use of the BCM numbering can be annoying.

To make it easier I decided to do a similar lookup table like I did for the Arduino.
Mapping Pin number variables to BCM numbers.
The code and an example is on GitHub.

It's straight forward to use.

Have PiGPIOPin.py in the same folder as your code or in the python path.

Put the following line at the top

from PiGPIOPin import *

Then instead of using something like

red = LED(17) # 17 is the BCM number that is at board pin 11

use

red = LED(PIN11) 

Each BCM number is mapped a PIN* variable.

The rest of the code then works as normal.

Using this gives the option back to use board pin numbers and not BCM numbers.

White Wii Nunchuck shaped Bluetooth Joystick - £1.85/£1.99 on eBay

When I attended PiWars (a great event for people who like to build robots using the Raspberry Pi) earlier this year I saw a whole range of controllers being used for controlling Raspberry Pi based robots. With many using USB dongle ones and others using Bluetooth or even apps on phones.  Expecting to see some BlueDot next year a great Android App for controlling things over Bluetooth.

Since my phone is iPhone (too long to explain) BlueDot isn't an option for me and with my continuing goal of finding cheap solutions to a problem I found a £1.85 Bluetooth controller from eBay - 3D Bluetooth Virtual Reality Glasses VR BOX Game Remote Control Gamepad Handles

What I liked about it is that it uses AAA batteries so if at an event the batteries died I could swap them out. No need to wait for recharging.

It's billed as being for mobile gaming and virtual reality and no mention of working with a regular computer or even Raspberry Pi, so I took a punt for £1.85, well actually £3.70, as I bought two. (walking on the wild side). 

eBay order confirmation

NOTE: The listing I bought from has ended but the same seller has a new listing at £1.99

I've seen some similar listing with switches on the side.  This is not the model I have bought. Mine has no switch.

What it looks like on eBay listing

They arrived and actually look good.  Plastic is definitely cheap, but they don't feel flimsy.
Below are a couple of pictures of the real thing.  A little different to the render but I'm happy..

Top. Joystick, power button, mode change button and 4 facing buttons.

Front has 2 additional buttons for when held straight rather than sideways

Time to start testing.

Setting up a new Raspbian image and using Raspberry Pi ZeroW I added the two AAA batteries and it came on. Blue light flashes to say ready to pair.

Using the Bluetooth Add Device in Raspbian the device VR BOX was found and paired successfully.  The unusal name actuallymakes sense as the listing on eBay is for "3D Bluetooth Virtual Reality Glasses VR BOX Game Remote Control Gamepad Handles"

Bluetooth on Raspbian paired with VR BOX

From the eBay listing and the single sheet of instructions the Gamepad/Nunchuck has 4 modes that you select with a combination of the @ and the relevant button.

A : Function Select (Music Video Mode.)

B : Function Select (game mode)

C : Function Selection (VR video self-timer mode.)

D : Function Select (mouse self-timer mode.)

It starts up in Music mode, so to use as a gamepad you have to change this after it pairs.

As I wanted to test in game mode I did [@]+[B]

I previously created a small python/pygame program to help with the testing.  It's available on GitHub.

I downloaded it to the PiZeroW (one of these days I'll do the proper git clone thing) and ran the program.

I run from the command line as the terminal window prints the details in text while the pygame window gives a graphic representation of the gamepad so I can see if multiple button presses are possible and which button numbers are pressed.  The code includes an analogue joystick so it will show the full range of movement for the gamepad joystick.

python2/pygame gamepad tester

Pressing the buttons the appropriate red square appeared and the terminal window stated which button was pressed or released.  Success! It's being detected as a gamepad and the buttons are working.

I then used the joystick which looks like an analogue stick you see on many projects. Only it's not. The joystick is digital.  Up, Down,Left,Right.  No range in values.  Except for a strange thing.
The positive values are 0.999969482422 and the negative values are -1, so you can't test for 1 for down and right when in gamepad (sideways) mode as 0.999969482422 is not 1. A little gotcha for coding.

The different modes

As listed above there are 4 different modes for the controller.

[@]+[A] for music
Nothing happened on the Pi. I haven't figured out what Bluetooth Music Mode is yet.
I tried this mode with my phone and it does provide volume up/down, mute an play so does what is expected with the target device.

[@]+[B] game mode
This is gamepad in horizontal mode, like a traditional controller with the joystick on the left and the buttons on the right.
For example, if you push up the Up joystick is detected

[@]+[C] VR video self-timer mode
This is a gamepad in Nunchuck mode. So vertical.
For example, if you have the controller held vertically and press up then Up Joystick is detected.
All the buttons are the same as for game mode.

[@]+[D] mouse self-timer mode
Guess what the joystick operates like a mouse held like a Nunchuch (vertical) with the lower front button (trigger) being left click and the higher front button (trigger) being right click.
In mouse mode buttons A and B still get recognised as gamepad buttons so that could be useful.Not sure how or when but extra buttons are always useful. 

Button combinations

In game mode some of the buttons could be pressed at the same time while others could not.

@ and Power are reserved so have no button function.

Bottom trigger and top trigger could not be pressed at the same time. Lower trigger always took priority even if upper was pressed first.

Bottom trigger could be pressed with any of the face bottoms (A,B,C,D). Same for Top Trigger.

A could be pressed with C, but not B or D. A stays active and the others do not show.
If you press B or D first and then press A, A will be activated and the other will be released.

B and C can be pressed at the same time

D is over ridden by all face buttons, so if you have D pressed and then press any of the other their function is activated and D is released.

Also, either trigger and two button face combinations that were noted to work above will also work.
So, if you need 2 buttons at the same time and one is the master and the second one needs to be one of 4 I'd recommend using a trigger as the master and the face buttons as the secondary as this works for all face buttons.
If you need 3 buttons then there are a small number of combinations that will work.
Top button, A and C worked for me.

Future Note: I have a feeling this section may need a chart of some nature. Need to figure out how to represent it.

For Python/Pygame and I expect other system the buttons are numbered:

Gamepad Mode


Face button arrangement
  A 
C   D
  B


Top Trigger: button 7
Bottom Trigger: button 6
A: button 4
B: button 0
C: button 3
D: button 1

VR mode (Nunchuck)

Face button arrangement

  C

B   A

  D

Top Trigger: button 7
Bottom Trigger: button 6
A: button 1
B: button 3
C: button 0
D: button 4

When I saw it changed I thought the button values would have turned clockwise 90 degrees so the buttons were in the same position (top, left, right, bottom) would have the same values but they don't. Top and bottom shift correctly, but left and right are mirrored.

Where did 2 and 5 go.  I wonder if they're on the board and not broken out. Might be a tear down thing

Summary

For £1.85, or £1.99, last time I checked if your need is digital controls then I think this is a hit.  It paired easily. The instructions though really sparse are enough to change modes.
With a phone it does the media things promised from mode A and on the Raspberry Pi and expect and device that supports a Bluetooth Gamepad and Mouse it does exactly what it says on the tin.

For controlling robots it's ideal (except for no analog).
Joystick for direction control and then buttons for other functions. Maybe take a picture, fire a missile, change mode from piloted to auto mode for different challenges at an event like PiWars.
With the advantage of using regular AAA batteries there is no fear that at an even the controller will run out of power and need to be charged.


A little but extra

As each controller having a unique Bluetooth Device ID it's possible to set up a cronjob on Linux to  pair with a specific gamepad when the Raspberry Pi (ZeroW) is booted/rebooted so  at events if you had 5 robots, 5 controllers each controller would be set up to work with a specific controller
It's not too complicated to do.

Get the device ID for the VR Box using the command bluetoothctl
Mine was FF:FF:70:00:76:8B

Run crontab -e
Select your editor if running for the first time. I use Nano

Go to the end and add the line

@reboot echo "connect FF:FF:70:00:76:8B" | bluetoothctl

If using Nano do a [ctrl]-[x] to exist and 'y' to save.
Reboot an you're done.

This will try to auto pair when the Pi boots.

You can also do a cronjob to continuously try to reconnect and not just at boot.
This is useful if the Pi has completed booting before the gampad has been turned on or if the controller hasn't been used for 10 minutes or in pairing mode fails to pair after 3 minutes and so needs to repair when the controller is turned back on

Raspberry Pi 3 with Google AIY VoiceHat

I was lucky enough to get a copy of Issue 57 of The MagPi with the VoiceHat from Google on the cover.

This is a great bit of kit with Raspberry Pi Hat, speaker, microphone, and a cardboard box to put it in.
For a bit of fun I fitted it into a cardboard R2D2 that I had from before Christmas.

This is not the droid you're looking for

After doing the usual of asking it to tell a joke and give me the weather and details of what's nearby I was wondering what I could use the VoiceHat for.

We have an Amazon Dot and it's main purpose in the house is playing radio station.  I tried this out and nothing played.  Seems streaming radio support isn't built in.

Then keeping up with what others were doing Mike Redrobe posted on the Raspberry Pi forum that he had it playing YouTube audio. https://www.raspberrypi.org/forums/viewtopic.php?f=114&t=182665

With a bit of assistance I got this working.  If you're careful with the name of the video you can get it to play fairly much any song.  My kids loved this.

But I still wanted to play streaming radio.  You know, one command and it's off rather than needing to keep telling it new songs to play.

In a later post Mike mentions using VLC as the player and armed with his example I began looking to see if I could get streaming radio to work.

I did. Yeah! Then I went on the trail to add playing podcasts.  Again a success.
You need to install VLC

sudo apt update
sudo apt upgrade
sudo apt install vlc

Radio Stations supported are:
Absolute Radio
Absolute 80s
Absolute 90s
Absolute 00s
Eagle Radio
BBC Radio 1
BBC Radio 2
BBC Radio 3
BBC Radio 4
Capital FM


Podcasts Supported are:
Good Job Brain
No Such Thing As a Fish
Freakonomics

Here is a little video of it working.  I recorded it in Portrait as the cardboard R2D2 it is in is portrait shared so if viewing on a phone will fill the screen, while of viewing on a computer it will have the side bars which is probably better than seeing the messy table.

The action.py file that's needed with the commands built in is available on GitHub
https://github.com/winkleink/RPi_AIY


Other useful bits and pieces

Knowing what Google is actually hearing

While setting up the radio stations Absolute 90s was interpreted by Google as Absolute 90s, but Absolute 00s was interpreted as absolute noughties
It took me a while to figure this out and command that helped me was:

sudo journalctl -u voice-recognizer -n 20 -f

This shows what's happening when you issue a command,
Here's a small snippet showing what the voice command is converted to.

Absolute 00s or is that Absolute Noughties

Make sure to stop and start the service after each change to action.py

sudo systemctl stop voice-recognizer && sudo systemctl start voice-recognizer

Want to add more radio stations

This website has a list of streaming radio stations and their urls.  This is the UK list.

http://www.listenlive.eu/uk.html

Stopping the playback

Since I'm using the button to stop the playback based on Mike Redrobe's code I decided to do the GPIO setup at the top so it is shared by all the commands rather than having it in each command.

The code is a while loop that keeps going until the button is pressed and then a kill statement to stop the process.  To be truthful I'm not sue how the kill bit works, I just know it does, so thank you to Mike for sharing.

while gpio.input(23):

    time.sleep(1)

pkill = subprocess.Popen(["/usr/bin/pkill","vlc"],stdin=subprocess.PIPE)

p.kill()

Doing the podcasts

Getting the most recent podcast to play is a bit more hacky than the radio stream as the radio stream is always the same while each podcast episode has a different url.  To achieve this I first had to find the relevant rss feed and then parse the file to find the start and end of the url to the mp3.  audioboom.com podcasts aren't too bad, but the Freakonomics one based off the feedburner rss was a little more complex as the url to the mp3 is actually a redirect url and they don't work.

https://www.podtrac.com/pts/redirect.mp3/audio.wnyc.org/freakonomics_podcast/freakonomics_podcast050317.mp3

You can see in the middle there is redirect.mp3 and then what looks like a path to a different website audio.wnyc.org

This meant the parser had to first find "/redirect.mp3/" and then from there find "mp3" to get the main bit for the audio.wnyc.org link.

Finally it needed to add back in "http://"

You can see how this is done in the code below.

url = 'http://feeds.feedburner.com/freakonomicsradio?format=xml' response = urllib.request.urlopen(url) data = response.read() # a `bytes` object text = data.decode('utf-8') startmp3 = text.find('/redirect.mp3/')+14 endmp3 = text.find('.mp3',startmp3+16)+4 if startmp3 > 0: command = "http://"+text[startmp3:endmp3]

Have a play and see what you can get the Raspberry Pi AIY to do.
Just be sure to backup any files you modify before changing them.
I didn't backup my action.py when I started playing but luckily google has made the original files available on GitHub https://github.com/google/aiyprojects-raspbian

I'm really looking forward to seeing how this grows and expands.

Just saw that https://twitter.com/k_tinkerer has been doing some great things with the AIY as well.  Worth checking out if you want to do more.

http://ktinkerer.co.uk/

I'll definitely be adding the shutdown and reboot commands from here.

Green Screen photo booth using Raspberry Pi

We've seen a number of photo booths here, here and even the All Seeing Pi being done with Raspberry Pi. All of these photo booths are based on taking a picture and maybe putting an overlay to add a banner or something like a funny hat or mustache.

My thoughts were could the Raspberry Pi 3 do Green Screen.  You know that special effect from the movies where the background is removed and a different image put in it's place.

As a kid I think the first time I remember seeing this was Superman.

How cool would that be to make your own version of the special effects used in big budget movies.

So, I started the search for tools under Linux that would permit the green screen to be done.

As a short summary green screen/chroma key is where a a single colour is removed from an image.

Most often it is green as modern cameras are more sensitive to green and a bright green works best as it's less likely to be a colour in a natural scene.  I remember when I was younger hearing it being done with blue screen as well.  

After a bit of looking I found Imagemagick a jack of all trades image processing tool.  It has a function to remove a single colour from an image and as importantly for my use includes a 'fuzzy' search for the colour which gave a bit of tolerance to the lighting.  

In the code the most important line is:

os.system('/usr/bin/convert -limit thread 4 ' + folder +'imagecam.png -fuzz '+fuzzpercent+' -transparent "#'+rgbnum +' " ' + folder + 'imagecamt.png')

I know there is a lot going on in there.  She short version is it takes imagescam.png, makes transparent the colour rgbnum with a tolerance of fuzzpercent and saves it as imagecamt.png

This forum thread was really useful in understanding how to use it.

Once I had my head around this it was then a matter of doing the rest of the code.

Take the picture

Remove the green

Layer a background and the image with the green removed. 

For testing I used some of my kids PlayMobil and a piece of A0 green card.  

All looks like it's working well even with the ability to change the background using the arrow keys

Now for the next level.

Scale it Up to Life Size !!!!

This of course means I needed a green screen background with standard that I bought from eBay.  No idea when I'll use the black or  white backgrounds that came with this kit, but I have them now.

And then Tweet the pictures.

For Tweeting I used tweepy and followed the excellent guide by Alex Eames @RasPiTV 

Finally, wouldn't it be great to have a little remote control and not have to rely on a keyboard.  Since the Raspberry Pi 3 has Bluetooth I thought this might be the ideal solution.  No wires and no messing about.  Since Pygame was already being used for the displaying of the images and I knew Pygame had joystick support built in this looked like the obvious choice.

Again, on eBay I found this small little Bluetooth gamepad and thought it would be perfect.  Super small which means you can have it in your hand but not interfere with your final picture.

Iddy biddy, teeny weeny, black gamepad 

My usual style is before bring a new feature into a project I like to test it standalone to make sure it works.  For the gamepad I created a small Python/Pygame program to test the gamepad 

It paired with the Raspberry Pi first time and worked perfectly with the gamepad test program.  So, 100% sure it will function with the chromaCam setup.

Now all the parts are in place.  PiCamera to take the picture.  Imagemagick to remove the background colour.  Pygame to merge background, foreground picture with green removed and finally an overlay with the background images changed with the keyboard or the super small gamepad.  (Oh yeah, the circular thing at the bottom is an analogue joystick)

The chromaCam set up got it's outing at the last Wimbledon Raspberry Jam.  Here are some pictures.

On the day I used a camera tripod and a lot of tie wraps to hold the Pi Display and the Pi Camera onto the tripod. I would definitely recommend a more secure mounting method 

Getting set up https://twitter.com/MrTomsWorld

Who doesn't love a bit of Harry Potter - https://twitter.com/rdhayler

Those Lions are dangerous

That doesn't look like a sensible thing to do - https://twitter.com/HackHorsham

Final notes.
If you did click the link above that explains Chroma Key/Green Screen then you'll have read that lighting is really important.  The goal is to one specific colour. If your lighting is uneven then due to shadows or folds in the green screen the green will be different giving varying results.

Taking out too much - https://twitter.com/Codepope

I'm sure the top of the Raspberry Pi logo isn't transparent

A few bits of rogue green - https://twitter.com/gowolade

If you want to make your own Green Screen Photo Booth then the code is available on GitHub

Final Thoughts:

Yes, this project worked and was great fun to build and see people using it.

For the project I limited the image size to 640x480 as even at that resolution it took about 2 seconds for the picture to be updated.  This meant it took a little bit of patients to get the picture you wanted before pressing the button to Tweet the image.

I took the set up to Hack Horsham as well but I didn't bring my own lighting and the lighting in the room was perfect for a Jam but didn't give enough contrast for chromaCam to work.  So, it didn't make the final cut and I stuck to Button Flash.

You can see the setup in the mannequin challenge video tweet. 

@Raspberry_Pi please can we get a retweet? Mannequin video of today's #horshampijam pre-opening :) #rjam #horshamdc pic.twitter.com/g9v0jl7NeM

— Hack Horsham (@HackHorsham) December 11, 2016

Again, this was a great learning experience for me and once the computing power for the Raspberry Pi enables it or access to the GPU is supported this will be amazing when the green screen transparency can be done in real time.  

I expect as new devices come out I'll be revisiting this project to see if the performance is improved. 

Making Games with Scratch and Sense Hat on Raspberry Pi

I'm a big fan of the Raspberry Pi Sense Hat and Scratch for doing interesting things and learning to code.
Previously I made a Sense Hat Cave Game using Python where you tilt the Sense Hat to move around as well as a Crane controller programmed in Scratch.
This time the goal was to create game that uses the Sense Hat as the display while programmed in Scratch.  The best of both world.  The goal for me was to lean to control the pixels a bit better in Scratch.

The result is Collect the Dots a simple game where you're a blue dot collecting red dots.  It's kind of like snake without the tail.

You control your dot using either the small joystick on the Sense Hat or use the keyboard on the computer.  Press Down to start the game.  You'll see in the video it tells you this on the Sense Hat, but if no Sense hat is attached and you're running on screen there is no prompt.

As can be seen in the video the on screen display mirrors on the Sense Hat dots, so either can be used.
Strangely even though the screen display is bigger I found it easier to play if I only looked at the Sense Hat display.
The game can also be played without the Sense Hat. Uploaded to Scratch website https://scratch.mit.edu/projects/144708660/

Embedded from the Scratch Website



You can download the code from GitHub

TIP: As the wonderful Cat Lamin points out in her blog post about using doing an animation on the Sense Hat using Scratch you have to run the code once to enable the sensors and capability of the Sense Hat.  So, the first time you run the program on a Raspberry Pi with a Sense Hat it may not work correctly.  Just stop it and start again and all will be perfect

A thought for an enhancement would be to control your dot by tilting the Sense Hat rather than using the joystick or keys.

Controlling screen brightness on pi-topCEED on Raspbian Jessie with guizero app and keyboard shortcut

I backed the pi-topCEED during the crowd funding campaign and have used it a lot since.

pi-topCEED

My kids also use it for homework and general Minecraft playing.

As I like to make things I have a number of microSD which means I regularly use it with Raspbian Jessie.

There are a couple of drawback to using Raspbian on the pi-topCEED.  The pi-topHUB doesn't shutdown the power completely leaving the backlight on and the Raspberry Pi in kind of a suspecd mode. The red LED is still on.  Also, there is no way to control the screen brightness.

Doing the usual Google to see if there was a way around this I came across this GitHub repository that looked like it would do the job.  https://github.com/rricharz/pi-top-install

It includes code to shutdown the pi-topHUB which also completely shuts down power to the display and to the Pi as well as provide a program called 'brightness' to control the screen brightness.

After following the instructions in the README.md I had the pi-topHUB shutting down correctly and if from the terminal I type brightness increase the screen brightness would go up and vice versa brightness decrease did what you'd expect.

All very good, but not very user friendly if you're running the GUI which is where I spend most of my time. 

With that in mind and having recently heard good thing about guizero (https://github.com/lawsie/guizero) which is based on tkinter and is said to make building GUI apps  in Python easier.

It looked to me like a simple app with 2 buttons [Darker] [Brighter] is all I needed so I read up a little on guizero.  Using the App using grid layout example (https://lawsie.github.io/guizero/app/) I soon has a small app that did exactly what I wanted.
Code available on Git Hub (https://github.com/winkleink/pi-top-brightness)

The program itself is quite short. Code below.  This makes 2 buttons.  Button1 and Button2.  When you press them they run the relevant system comment to change the brightness. 

from guizero import *

from subprocess import call

def brighter():

    call(["brightness", "increase"])

    

def darker():

    call(["brightness", "decrease"])

    

    

app = App(title="pi-top", height=50, width=145, layout="grid", bgcolor=None)

button1 = PushButton(app, brighter, text="Brighter", grid=[0,1])

button2 = PushButton(app, darker, text="Darker", grid=[0,0])

app.display()

Here is a video showing it working.

After a quick chmod +x  pi-top-brightness-gui.py the program was executable and so I could run it directly.

Then I added the program to the main menu under the System Tools section.

In the video you can see I have a pi-top icon.  This I took from their Twitter account (https://twitter.com/GetPiTop)  I expect they'll be OK with that as I'm adding even more branding to my pi-topCEED.

I explained in a recent post on backing up Minecraft Worlds how to add a program to the menu (http://www.winkleink.com/2016/07/minecraft-pi-backup-worlds-on-exit.html)

It's great to have a little gui app to change the brightness of the screen and even better to learn a new skill with guizero.

One thing I didn't mention is that when I rebooted the Raspberry Pi the first time after installing the programs the screen brightness was far lower than I wanted it be by default.

To fix this I added a single line cronjob.  Crontab with cronjobs is a way to schedule when programs run automatically with one of the options being to run at boot up. It's a simple way to get something running each time you login. It's the system used by people who lets say want to check their network connection every hour.  Just setup a cronjob to run every hour and it will take care of it for you.   I used this previously to enable the Bluetooth keyboard and trackpad or the NexDock. (http://www.winkleink.com/2016/10/nexdock-thoughts.html)

So, I used crontab to set the brightness of the screen to 8 on startup.

In the terminal type:

crontab -e

If this is your first time it asks which editor you want to use.  I do [2] for nano.

Then the crontab file is opened where you put the jobs you want to run.

There are some comments in the file to help you get started, but if you want to do serious scheduled jobs then it's worth 

Go to the bottom of the file and type

@reboot brightness 8

Then the usual nano [CTRL]-[x] to save and close.  Answering [y] to save the file with the same name

Now when I start up the pi-topCEED the default brightness is '8' which suits me.

Finally, finally, the rricharz GitHub explains how to set the keyboard shortcuts for the pi-top laptop so the brightness keys work.  All good if I had a pi-top laptop, but I have a pi-topCEED where it's bring your own keyboard and the one I'm using doesn't have any fancy keys.

So, I looked up how to add keyboard shortcuts.  Again, it ends out to be not too hard.  Just added a couple of entries into a config file.

First thing I had to do is decide what key combination I wanted to use. I settled on:
[Shift]-[Windows Key]-[Up Arrow] for brighter

[Shift]-[Windows Key]-[Down Arrow] for darker

To do this you need to edit the lxde-pi-rc.xml file.

The file is a in a hidden folder in your home folder. If using the default user pi then the following command will open it 

nano /home/pi/.config/openbox/lxde-pi-rc.xml

As the file is in the home folder it doesn't need sudo to edit it

Then scroll down to the keyboard section and add the following to the end.

Easiest way is in nano find the </keyboard> text using the command [Ctrl]-[w] to do a Where is

Make sure you use spaces for the indent and get the <keybind> to line up with the other <keybind> entries

    <keybind key="S-W-Up">
      <action name="Execute">
        <command>brightness increase</command>
      </action>
    </keybind>
    <keybind key="S-W-Down">
      <action name="Execute">
        <command>brightness decrease</command>
      </action>
    </keybind>

To finish like above use [Ctr]-[x] to save and close.

To test select [shutdown] in the drop down menu and then [logout].

No need to reboot to enable the keyboard shortcuts.

Once you log back in the lxde-pi-rc.xml setting will be re-enabled and the 2 new key bindings will be active giving you the ability to change the brightness of your pi-top/pi-topCEED using [Shift]-[Windows Key]-[Up Arrow] and [Shift]-[Windows key]-[Down Arrow]

This has been a fun little project to improve the use of the pi-topCEED.
I like the work rricharz has done getting the pi-topHUB to turn off completely and to control the brightness as well as Laura Sach has done to make guizero so easy to use.

With the help of other peoples effort I now have the pi-topCEED completely shutdown as well as the Raspberry Pi and the ability to change the screen brightness using either a little gui app or with the keyboard.  Not a bad result for a couple of hours.

If you have any questions let me know in the comments.