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 GitHubalong with other Jam worksheets.
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.
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.
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.
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.
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).
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
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
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
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.
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
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.
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
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.
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.
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_tinkererhas been doing some great things with the AIY as well. Worth checking out if you want to do more.
We've seen a number of photo booths here, here and even the All Seeing Pibeing 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.
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
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.
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.
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.
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.
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.
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.
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
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.
IMPORTANT: The code in this blog post is the original code which does work but may not have all the enhancements. If you're building your own I recommend grabbing the code from GitHub.
GitHub link: https://github.com/winkleink/buttonFlash
Update: 19th September: Took buttonFlash to the Cambridge Raspberry Jam on the 17th of September and it got a proper outing.
UPDATE: 25th August:
Made Raspberry Pi program look prettier
Added sound effects
A few years ago I thought it would be fun to come up with an outdoor game that would get people running around. The Whack-a-Mole/reflexes button game came to mind and this is the result. A game where you have to press buttons as quickly as possible.
Whack-a-Pi was in constant play at the Raspberry Pi 4th Party.
The concept for buttonFlash is similar to Whack-a-Pi but with the ability for the buttons to be much further apart. Goal is to get people running around. With the buttons further apart there was no way I was going to be managing physical wires as it would be a trip hazard and I didn't want to have to manage that many wires. So, wireless communication between the base and the buttons seemed the obvious choice.
Most fields don't have wifi. I could bring along my trusty Vocore and create a local WiFi hot spot but again I want this to be simple to set up and use.
VoCore. Basically guts of a Wifi router
So, I thought the NRF24L01 would do the trick. They're a really cheap transceiver. They can transmit and receive signals making them ideal for short range two way communication.
On the Arduino I used the RF24 library. If you've the latest version of the Arduino IDE you can install this through the library manager or if you prefer you can go old school and download it from the GitHub repository at the link above. More details on using the NRF24 with Arduino
The Arduino side was relatively straightforward to get working while the Raspberry Pi side had me stumped for a while. Then earlier this year I had a breakthrough when I met +Elliot Pittam. He had seen the first Wimbledon Raspberry Jam and was interested in coming along. On email we discussed what we were working on and Elliot said he was using the NRF24L01 with the Pi and Arduino. We then met at a HackWimbledon event where he showed me his set up and shared his working code. Elliot helped me sort my circuit and pointed me to 2 great videos on using the NRF24L01 with both Arduino and Raspberry Pi.
Tutorial 34 - Part 1
Tutorial 35 - Part 2
With Elliot's assistance I successfully had the Raspberry Pi communicating with the Arduino.
Many of the example I found did not clearly identify which pins on the Arduino or Raspberry Pi were connected to which pins on the NRF24L01. Therefore, below is the wiring I used for the Raspberry Pi and the Arduino with the code provided. So, it all matches up nicely.
NRF Pi GPIO Pin
VCC 3.3V 1
GND GND 6
CSN GPIO8 24
CE CPIO17 11
MOSI GPIO10 19
MISO GPIO9 21
SCK GPIO11 23
NRF Arduino VCC 3.3V GND GND CSN Digital 10 CE Digital 9 MOSI Digital 11 MISO Digital 12 SCK Digital 13
For the Arduino to keep it compact I went with Arduino Nano compatible board on a small 170 pin breadboard. Easy build and easy maintenance.
It's important to know these compatibles use the CH340G serial chip which is different to the Arduino branded. You will need additional driversto get these working with some computers.
To make each of the buttons base I needed a suitable container to hold the button and the rest of the electronics and of course the button. I'd seen these great 60mm buttons with LEDs built in so I order some. Again from eBay UK these are about ~£7.00 for five.
RED 60mm LED button
The ones I ordered are 12V rated which is the power for the LED. Opening it up these things just have a standard LED and a current limited resistors. The resistor was a 460 Ohm for the 12 volts. Without knowing the specific LEDs and their voltage drop and maximum current I played it safe and replaced the 460 Ohm with 150 Ohm resistors. The buttons did light very dimly with the 460s but were far brighter with the 150 Ohm. Below is the button being taken apart.
button in place
unscrew the button/LED assembly
pull out the LED (like Christmas lights)
remove LED with resistor on Anode (+ side, other goes to GND)
solder on replacement resistor and put it all back together
To test the LED at each stage I ran an Arduino with the blink sketched and wired the LED across pins GND and 13. Once all reassemble with the wires attached again I tested to make sure I didn't mess things up in putting it back together.
Next, for each Arduino I wired the NRF24L01 as per above. The LED was wired to Pin 2 and Button was wired to Pin 3. In code I activated the internal pull up resistor so the button is held high until you press it and then it goes low.
it all wired up.
As the Raspberry Pi needed to send a message to the Arduinos to let them know which one is to activate their button and wait for it to be pressed before replying I came up with a simple message that is extendable. Basically, the number of the Arduino followed by 'P' Examples: 1P, 2P, 3P, 4P, 5P
This would be the message sent out.
All Arduino would receive it and then using a simple IF statement would decide if it means they are to be activated. If not go back to listening. If yes light the button and wait for it to be pressed. Once pressed reply to the Raspberry Pi that the button has been pressed.
In this way the Arduino are dumb. They only respond to a request for the button and reply it's been pressed. They don't care if they are the first, second, third,... button to be pressed in the game. All that is managed at the Raspberry Pi.
To make it easier to setup and to test I included a test mode.
When you press 't' it sends the test message and all the Arduino flash their LEDs 5 time. Then Arduino 1 (as there will always be at least 2 Arduino) replies that it is completed.
The Raspberry Pi doesn't do anything with this message as the test is to see if it is sent and replied to which the users sees in the console.
This means Button/Arduino 1 has slightly different code to all the rest of the buttons.
Button/Arduino 1 code with the extra bit for Arduino 1 only highlighted in RED
For each Button/Arduino the text highlighted in BLUEneeds to be changed to matched the relevant reference in the Raspberry Pi list. This text is the same in all 3 locations so you can do a Find/Replace to do it in one go.
Serial.println("We sent our message: " + String(text));
}
// Test scenario
if (stringMessage == "TEST") {
for(x=0; x < 5; x++){
digitalWrite(ledPin,HIGH);
delay(500);
digitalWrite(ledPin, LOW);
delay(500);
}
Serial.println("Test completed");
const char text[] = "Test done";
radio.write(text, sizeof(text));
Serial.println("We sent our message: " + String(text));
}
}
delay(100);
}
On the Raspberry Pi side the code is a little more interesting as it sets up the NRF24L01 and then creates a graphical window using pygame and finally runs the game. At this stage it displays Score and High Score.
The steps to get the Raspberry Pi ready are:
Wire up the NRF24L01 as per above
Use the Raspberry Po configuration program to enable SPI (you have to reboot after this)
Then run the following commands.
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python-dev python3.dev -y
I'm assuming you're in hour home directory for the rest of this.
mkdir buttonFlash
git clone https://github.com/Gadgetoid/py-spidev
cd py-spidev
sudo python setup.py install
sudo python3 setup.py install
cd ..
git clone https://github.com/BLavery/lib_nrf24
cd lib_nrf24/
cp lib_nrf24.py ~/buttonFlash
cd ..
You should now have SPI working with the python SPI libraries installed for Python 2 and 3 as well as the required lib_nrf24 for working with the NRF24L01 from python.
Finally the library file is copied to the buttonFlash directory.
Copy the Raspberry Pi code into the buttonFlash directory and run it.
Here is a short example of it running after the initial build.
With the electronics sorted and the programs functioning the next requirement was a housing for the buttons. I thought I found the perfect one when I got this spaghetti container from Home Bargains. It all fit comfortable and the button was really secure.
Only problem was when I went back to get more they were out of stock with no idea when/if more would be coming in. Then I saw the Pringles can and tried it out and it worked. Pringles cans for the win.
Oh, and I had to eat another 4 cans of Pringles to get the 5 required.
As this is designed to be played indoors or outdoors I needed to fina a way to make them stable when placed in a field. I went super simple and bought 150mm bolts with nuts and passed them through the bottom of the Pringles cans. You'll notice I numbered each can and there is also a colour listed. I bought 5 different coloured breadboards so I could tell which Button/Arduino was in each can.
You can see the bottoms of the tubes are deformed a bit. Ends up Pringles cans aren't super strong. Means I have to re-tighten the nuts as they work lose. Wonder if an application from a glue gun will sort this out.
bottom of each Tube with bolt, number and colour
all the bits outside the can.
If you watched the video at the top or the video at the bottom you might have noticed the Pringles cans have a bit of a base to keep them stable for indoor use. In the rush to push the buttons the Pringles cans were falling over. The solution was some microwave pots that tapered from the bottom to the top turned upside down and with a hole cut int he bottom. This gives a nice wide base. If further stability is needed these pots could be filled with sand or stones to weigh down the bottom even more.
microwave pot used as base
This was an interesting build as I never used NRF24L01s before. Finding the information on how to get them to work and wire them up was interesting as most of the guides nearly provided the full details and they all seemed to provide slightly different information. So, I enjoyed solving that riddle and end up with a playable game that scales in the number of buttons and also the space.
This could be set up as 10 buttons on a table with all the cans tied to each other or as 20 buttons around the outside of a field. You'll hear in the video below that the Raspberry Pi can call out the button numbers. This definitely made it a bit easier as you quickly learn which button is which position. For outdoor use if it is very sunny I have a feeling the LEDs in the buttons will not be bright enough. So, next I will be adding more lights and indicators to the buttons so they can be identified outdoors.
Here's another video of the game being played at the Cambridge Raspberry Jam.
If you have any questions or comments let me know.
