#!/usr/bin/python # -*- coding: utf-8 -*- # qrmovie import time # need to use git://github.com/mozillazg/python-qrcode.git import qrcode from PIL import Image, ImageFont import ImageOps # uses bgreat's SPI code; see # raspberrypi.org/phpBB3/viewtopic.php?f=32&t=9814&p=262274&hilit=nokia#p261925 import nokiaSPI noki = nokiaSPI.NokiaSPI() # create display device qr = qrcode.QRCode(version=1, # V.1 QR Code: 21x21 px error_correction=qrcode.constants.ERROR_CORRECT_M, box_size=2, border=1) bg = Image.new('1', (84, 48)) # blank (black) image background # intro noki.cls() noki.led(0) time.sleep(3) for i in range(0,769,32): noki.led(i) time.sleep(0.04) # display is 14 columns by 8 rows noki.centre_word(1, 'scruss.com') noki.centre_word(3, 'presents') time.sleep(3) noki.cls() noki.centre_word(1, 'qrclock') noki.centre_word(2, 'the') noki.gotorc(3,3) noki.text("[Q]uite") noki.gotorc(4,3) noki.text("[R]ubbish") noki.gotorc(5,3) noki.text(" Clock") time.sleep(3) elapsed=0 start_time = time.time() while (elapsed<12): qr.clear() newbg = bg.copy() # copy blank background s = time.strftime('%Y-%m-%d %H:%M:%S') qr.add_data(s) # make QR Code of YYYY-MM-DD HH:MM:SS qr.make() qrim = qr.make_image() # convert qrcode object to PIL image qrim = qrim.convert('L') # make greyscale qrim = ImageOps.invert(qrim) # invert colours: B->W and W->B qrim = qrim.convert('1') # convert back to 1-bit newbg.paste(qrim, (18, 0)) # paste QR Code into blank background noki.show_image(newbg) # display code on LCD time.sleep(0.4) # pause before next display elapsed = time.time() - start_time noki.cls() noki.centre_word(1, 'for') noki.centre_word(2, 'more') noki.centre_word(3, 'details') time.sleep(3) noki.cls() noki.load_bitmap("blogpost-nokia.bmp", True) time.sleep(7) noki.cls() noki.centre_word(3, 'fin') noki.centre_word(5, 'scruss, 2013') time.sleep(1) for i in range(768,-1,-32): noki.led(i) time.sleep(0.05) time.sleep(1) noki.cls()
(This source, plus nokiaSPI class: qrclock-movie.zip)
Lines 43-58 show off the QR clock for a maximum of 12 seconds. Any more, and you’d get really bored.
The screen handling functions I used are:
- cls() — Clears the screen.
- led(brightness) — sets the backlight to brightness. For me, full brightness is at 768. A value of zero turns the backlight off. If you don’t have the screen LED connected to one of the Raspberry Pi’s PWM pin, this will either be full on (for any brightness >= 1), or off, for brightness=0. This is used to fade up the screen in lines 24-26, and fade it down far too theatrically in lines 72-74.
- show_image(PILImage) — display a single bit depth black and white Python Imaging Library object PILImage. This can be no larger than 84×48 pixels.
- load_bitmap(file, Invert) — load a single bit depth black and white BMP file of maximum size 48×84. If Invert is true, keep the colours as they are, otherwise swap black and white to make a negative image. nokiSPI flips images by 90°, so the image I loaded to show the URL of the blog post looks like this:
(I know, I could have generated this in code, but I’d already made the image using qrencode. I couldn’t be bothered working out the image size and offsets.)
The text handling functions I used are:
- gotorc(row, column) — move the text cursor to row, column. The screen only has 14 columns by 8 rows if you use the standard 6×6 pixel font, so keep your text short to avoid disappointment.
- text(text) — write text at the current cursor position.
- centre_word(row, text) — write text centred in row row. Since the text rows are a maximum of 14 columns, text with an odd number of characters will appear slightly off-centre.
There are many more functions in the nokiaSPI class; watch the demo, have a dig through the source and see what you can use.
Update 3: code for the demo video is here.
Update 2: In which I actually post working code.
Update: Eep! This post was featured on the Raspberry Pi blog today. Thanks, Liz!
And now for something completely different:
… a clock that isn’t human readable. You’ll need a QR code reader to be able to tell the time.
This, however, is not the prime purpose of the exercise. I was looking for an excuse to try some direct hardware projects with the GPIO, and I remembered I had a couple of Nokia-style surplus LCDs lying about that could be pressed into service. These LCDs aren’t great: 84×48 pixels, 3V3 logic, driven by SPI via an 8-pin header which includes PWM-controllable LED backlighting. They are cheap, and available almost everywhere: DealExtreme ($5.36), SparkFun ($9.95), Adafruit ($10 – but includes a level shifter, which you really need if you’re using a 5V logic Arduino), Solarbotics ($10) and Creatron (about $12; but you can walk right in and buy one). Despite being quite difficult to use, helpful people have written drivers to make these behave like tiny dot-addressable screens.
I’d been following the discussion on the Raspberry Pi forum about driving the Nokia LCD from a Raspberry Pi. Only when user bgreat posted some compact code that was supposed to run really fast did I dig out the LCD board and jumper wires. Building on bgreat’s nokiaSPI.py class and a few other bits of code, here’s what I built to make this singularly pointless clock:
#!/usr/bin/python # -*- coding: utf-8 -*- # qrclock - The Quite Rubbish Clock for Raspberry Pi - scruss, 2013-01-19 import time # need to use git://github.com/mozillazg/python-qrcode.git import qrcode from PIL import Image import ImageOps # uses bgreat's SPI code; see # raspberrypi.org/phpBB3/viewtopic.php?f=32&t=9814&p=262274&hilit=nokia#p261925 import nokiaSPI noki = nokiaSPI.NokiaSPI() # create display device qr = qrcode.QRCode(version=1, # V.1 QR Code: 21x21 px error_correction=qrcode.constants.ERROR_CORRECT_M, box_size=2, border=1) bg = Image.new('1', (84, 48)) # blank (black) image background while 1: qr.clear() newbg = bg.copy() # copy blank background s = time.strftime('%Y-%m-%d %H:%M:%S') qr.add_data(s) # make QR Code of YYYY-MM-DD HH:MM:SS qr.make() qrim = qr.make_image() # convert qrcode object to PIL image qrim = qrim.convert('L') # make greyscale qrim = ImageOps.invert(qrim) # invert colours: B->W and W->B qrim = qrim.convert('1') # convert back to 1-bit newbg.paste(qrim, (18, 0)) # paste QR Code into blank background noki.show_image(newbg) # display code on LCD time.sleep(0.4) # pause before next display
(Convenient archive of all the source: qrclock2.zip, really including bgreat’s nokiaSPI class this time …)
To get all this working on your Raspberry Pi, there’s a fair amount of configuration. The best references are bgreat’s own comments in the thread, but I’ve tried to include everything here.
Enabling the SPI kernel module
As root, edit the kernel module blacklist file:
sudo vi /etc/modprobe.d/raspi-blacklist.conf
Comment out the spi-bcm2708 line so it looks like this:
Save the file so that the module will load on future reboots. To enable the module now, enter:
sudo modprobe spi-bcm2708
Now, if you run the
lsmod command, you should see something like:
Module Size Used by spi_bcm2708 4421 0
Installing the WiringPi, SPI and other required packages
WiringPi by Gordon is one of the neater Raspberry Pi-specific modules, as it allows relatively easy access to the Raspberry Pi’s GPIO pins. For Raspbian, there are a few other imaging libraries and package management tools you’ll need to install here:
sudo apt-get install python-imaging python-imaging-tk python-pip python-dev git sudo pip install spidev sudo pip install wiringpi
Installing the Python QR code library
Finding a library that provided all the right functions was the hardest part here. I ended up using mozillazg‘s fork of lincolnloop‘s python-qrcode module. mozillazg’s fork lets you use most of the lovely PIL methods, while the original hides most of them. Since I had to do some image compositing and colour remapping to make the image appear correct on the Nokia screen, the new fork was very helpful.
To install it:
git clone git://github.com/mozillazg/python-qrcode.git cd python-qrcode/ sudo python ./setup.py install
The tiny 84×48 resolution of the Nokia screen doesn’t give you many options for sizing QR codes. For the time display of the clock, a 21×21 module Version 1 code with two pixels per module and one module margin just fits into 48 pixels. Using a medium level of error correction, you can fit the 19-character message (such as “2013-01-19 18:56:59″) into this tiny screen with a very good chance of it being read by any QR code reader.
(In the video, there’s a much larger QR code that’s a link to this blog post. That’s a Version 7 code [45×45 modules] at one pixel per module and no margin. This doesn’t meet Denso Wave’s readability guidelines, but the Nokia screen has large blank margins which seem to help. It won’t read on every phone, but you’re here at this link now, so you don’t need it …)
Wiring it all up
(Do I really need to say that you’ll be messing around with the inner delicate bits of your Raspberry Pi here, and if you do something wrong, you could end up with a dead Raspberry Pi? No? Okay. Just make sure you take some static precautions and you really should have the thing shut down and powered off.)
You’ll need 8 female-female jumper wires, and also some kind of pin header soldered in (I used right-angled ones). Note that the thick border of the LCD is the top of the screen. These boards are made who-knows-where by who-knows-whom, and there’s a huge variety of labels and layouts on the pins. My one appears to be yet another variant, and is labelled:
This is how I wired it (from comments in bgreat’s code and the GPIO reference):
LCD Pin Function Pi GPIO Pin # Pi Pin Name ============= ============= =============== ============= 1 VCC Vcc 1 3.3 V 2 GND Ground 25 GND 3 SCE Chip Enable 24 GPIO08 SPI0_CE0_N 4 RST Reset 11 GPIO17 5 D/C Data/Command 15 GPIO22 6 DNK(MOSI) Data In 19 GPIO10 SPI0_MOSI 7 SCLK Serial Clock 23 GPIO11 SPI0_SCLK 8 LED Backlight 12 GPIO18 PWM0
Wire it up, and fire up the program:
Yes, code that accesses GPIO needs to be run as root. Pesky, but helps you avoid running code that accidentally scrams the nuclear power station you’re controlling from your Raspberry Pi …
I have, of late, been rather more attached to QR Codes than might be healthy. I’ve been trying all sorts of sizes and input data, printing them, and seeing what camera phones can scan them. I tried three different devices to scan the codes:
- iPhone 4s – 8 MP, running either i-nigma (free) or Denso Wave’s own QRdeCODE ($2). QRdeCODE is better, but then, it should be, since it was created by the developer of the QR Code standard.
- Nexus 7 – 1.2 MP, running Google Goggles.
- Nokia X2-01 – Catherine‘s new(ish) phone, which I can’t believe only has a 0.3 MP VGA camera on it. Still, it worked for a small range of codes.
QR Code readability is defined by the module size; that is, the number of device pixels (screen or print) that represent a single QR Code pixel. Denso Wave recommends that each module is made up of 4 or more dots. I was amazed that the iPhone could read images with a module size of 1 from the screen, like this one:
On this laptop, one pixel is about 0.24 mm. The other cameras didn’t fare so well on reading from the screen:
- iPhone 4s – Min module size: 1-2 pixels (0.24-0.48 mm/module)
- Nexus 7 – Min module size: 2-3 pixels (0.48-0.72 mm/module)
- Nokia X2-01 – Min module size: 3-4 pixels (0.72-0.96 mm/module)
So I guess for screen scanning, Denso Wave’s recommendation of 4 pixels/module will pretty much work everywhere.
I then generated and printed a bunch of codes on a laser printer, and scanned them. The results were surprisingly similar:
- iPhone 4s – Min module size: 3-4 dots (0.25-0.34 mm/module)
- Nexus 7 – Min module size: 4-5 dots (0.34-0.42 mm/module)
- Nokia X2-01 – Min module size: 8-9 dots (0.68-0.76 mm/module)
A test print on an inkjet resulted in far less impressive results. I reckon you need to make the module size around 25% bigger on an inkjet than a laser, perhaps because the inkjet is less crisp.
(and while I was at it, I created a new field for ham radio operators: X-CALLSIGN. Why not?). I even encoded some locations in QR Codes.
Just to show you what qrencode can do, here’s a favourite piece of little prose:
Put me out to pasture, my conference swag skills are failing.
I picked this up at Solar Power International:
I thought I was picking up a USB memory stick, as I’d nabbed one in the same form factor before. Break off the backing card at the hinge, and you’ve got a nice tiny data store like the Kingmax ones I used to use.
On plugging it into my Mac, a couple of icons bipped on my dock, then Skype opened. Wat? More importantly, there was no storage to be seen, so once my virus fears had subsided a bit, I was determined to find out what this pointless piece of plastic was doing.
The stick identified itself to the system as an Apple keyboard (USB ID 05ac:020b), and spits out the following characters (captured by cat and xxd on my Raspberry Pi):
0000000: 1b72 1b5b 317e 1b5b 3477 7777 2e62 757a .r.[1~.[4www.buz 0000010: 7a63 6172 642e 7573 2f73 6365 2d32 3230 zcard.us/sce-220 0000020: 0a .
After reading about evil USB dongles, it seems that the Ctrl-R keypress it's sending is the Windows "Open Browser" command, and then opens the url
www.buzzcard.us/sce-220. This link redirects to
www.plugyourbrand.com/gosolar_sce/index.html?u=220, which appears to do some Flash/JS stuff which I don't want to understand.
The funny thing is, the card has the perfectly respectable www.GoSolarCalifornia.ca.gov (well, respectable if you consider a US .gov website as such) link printed on it. Even printing a card with a QR code linking to that address would be less opaque.
As is, a bunch of plastic was wasted in vain just to save people typing an URL. We're all going to die, and it really is your fault ...