This threw up an interesting problem because I wanted to measure the power consumption of the Pi both with and without my wifi dongle. But if I pull out the dongle, I’m not sure it will reconnect when I re-attach it, and then I won’t be able to communicate with it (I was using it headless – no monitor/keyboard). Eventually it hit me.
Delayed shutdown to the rescue
One solution was to to measure the power consumption with the dongle in, then sudo shutdown -h 5
which tells the system to shut down in 5 minutes. So then I pulled the dongle out and measured power consumption again. Then waited for it to shut down, which it did.
Great. It all went according to plan and the Pi model A uses 0.81 Watts with the Edimax wifi dongle in and 0.51 Watts without it. This is at idle. (Model B uses 2 Watts).
Ok let’s start again then
So then I plugged the wifi dongle back in, without pulling the power cable, and I was pleasantly surprised to see the Pi boot all by itself. I knew it could be made to boot by shorting header P6 (if fitted) but this was a new one to me. Bring your Pi back from suspend by plugging in a USB wifi dongle. Nice. I haven’t seen this documented anywhere either.
Only Rev 2 model B and model A
This doesn’t work with Rev 1 Pis. It works with Model As and Rev 2 Model Bs, which, as far as I know, use the same board.
And here’s a little video to prove it
This will probably work with other USB devices as well, but I haven’t tried others yet. Leave a comment if you make it work with other devices
The Milton Keynes Jam is rather special because it is held at the National Museum of Computing, which is on the same site as Bletchley Park. They’ve got the oldest working digital computer in the world – the WITCH.
Also there is Colossus – the famous code-breaking computer from World War 2. If you like computers, it’s an awesome place. (And if you don’t like computers what on earth are you doing reading this page?)
It’s the perfect home for a Jam.
What’s in the Jam then?
We usually have introductions, then about 2 hours of open session, where people lay out their demos and talk to each other. There is a perfect opportunity to ask questions and get help with something you might be stuck on. It’s great for meeting people, getting inspired and sharing ideas too. We usually have several teachers present and several experts in various areas. If you’re having trouble with a software or hardware project, bring it along and someone will probably be able to help you.
If you are a beginner it’s a great opportunity to come along and see what the Raspberry Pi is all about.
After the Jam, you can go round the museum. If it’s your first visit to the Jam, you can visit the museum free of charge.
BBC Technology program Click just used a segment from the video I posted a couple of weeks ago on the model A release. It’s right in the middle of this 6 minute video. About 8 seconds starting around 4:28. It’s a real shame I was out yesterday afternoon when Liz was trying to get in touch – I could have given them a much nicer 1080i HD version.
Watch the whole 6 minutes though, it’s a good one about hackers, makers and Pi users.
Matt Hawkins from Raspberry Pi Spy has done the leg-work enabling Pi users to use a Wii controller – along with a Bluetooth USB dongle to send inputs to the Raspberry Pi. It uses a Python library called “CWiid” (I imagine this is pronounced “seaweed”).
This is awesome because the Wii controller has 11 different digital inputs. When you consider combinations of inputs, that gives you a lot of extra possible “input commands” to play with.
Theoretically*, with 11 buttons, there are 55 different 2-button combinations (11C2). That should be enough for most uses. If you need more than that, you could use 3-button combos.
Here’s a little video of some Wiimote controlled Gertboard madness
And, happily, they worked first time with my Tesco’s own-brand Technika nano Bluetooth dongle, which has a Pi-compatible chipset. I bought mine in Tesco Extra for about £4.
This is what to look out for in Tesco
So I think we can look forward to seeing a proliferation of Wii remote controlled Raspberry Pi programs in the near future.
What will you do with yours?
Matt’s going to control an RC car with his. After my initial Gertboard experiments, I’d like to see if it’s possible to use two controllers for an interactive Quiz.
What will you do with yours?
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* In practice, the direction controller slightly restricts the number of choices, e.g. you can’t have opposites pressed simultaneously, but we’ll ignore that.
I was keeping an eye on the RS and Farnell sites on Monday morning because I’d heard a ‘reliable whisper’ that the model A was launching this week. I didn’t know what day, but I figured it might be Monday. No sign of anything early morning, but then I forgot and didn’t see Liz’s announcement on the Pi blog until a couple of hours after they went live. By that time, RS was showing back order, but Farnell had stock levels of ~1800, so I snagged one. I got a “shipped” email about 3 hours later and, just for fun, checked stock levels again. ~1000 this time. So, not quite the mayhem of a year ago, but healthy sales nevertheless.
Another one?
I was going to buy another Pi anyway after damaging the spi ports on one of my Rev 1 Pis last week, but I held back after hearing that the model A was imminent. Might as well have one of those instead. It’s just as good for GPIO stuff and I can set it up on wireless or use my USB-RS232 tty terminal adaptor to login. Of course, there’s always the good-old keyboard and monitor approach as well.
So what’s it like then?
It’s a lot like a Rev 2 model B, but without the network socket and chip and only one USB port and the same 256 Mb RAM as the original model A. First impression on handling is that it feels a lot lighter. I weighed a model A and a model B. Model B weighs 41g, model A weighs 31g. That will please those who are going to put them in balloons, planes and ‘copters. “Raspberry Pi model A, the one ounce computer” (nearly).
I’m not sure what the blue splodge is on my CE mark, but I’m going to attack it with some meths and a cotton bud. (It was ink or dye and came off very easily with meths, leaving no trace.)
Here are some photos (click to enlarge)…
Raspberry Pi model A front
Raspberry Pi model A rear
I’m glad it has the eight P5 header holes nice and empty of solder so I can try out the extra ports.
P5 header holes are empty
Made in the UK
Where else can you get a UK made, brand new linux computer for £20 delivered?
Here’s a short video tour
It works too
I just swapped out the SD card, wifi dongle HDMI lead and ribbon cable from another pi and fired up the model A. It worked just as it should do. cat /proc/cpuinfo reports revision number of 0008
This is part 2 of my review of the HDMI/VGA 1080 Ultimate HD Video Converter. It covers comparison of VGA and HDMI in the GUI; use of an old 1024 x 768 VGA monitor with the Pi; using a VGA projector to show a video; trying out an MHL adaptor with a phone and VGA monitor.
To complete the review, I set myself the following tasks…
see if I can get it to go full-screen in GUI by tweaking settings
do some side by side comparison photos of GUI with VGA and HDMI modes
check it out with an older monitor (not wide screen) and see how it copes
use it with the VGA projector at school to see if it does what I actually bought it for
try it with a MHL adaptor to see if I can show a video from my phone to a VGA screen (getting silly now, but why not?)
1) Full-screen GUI?
I changed my mind and decided it wasn’t good use of time to piddle about with this. I rarely use the GUI anyway, and if I did I’d go direct via HDMI. I’m pretty certain it would be possible to tweak this, but it might take a few reboots to get the settings spot on. You can see from the comparison photos that, at default settings, a bit less screen area is used with the VGA converter.
2) GUI VGA vs HDMI photos
First shot is VGA through the adaptor, second one is HDMI directly from the Pi. Exactly the same shooting position (tripod), aperture and shutter speed were used for direct comparison. The photos have not been tweaked, so you can see the real differences. Click on any photo to get full resolution.
Full screen VGA adaptor
Full screen HDMI striaght from Pi
You can see several differences.
The HDMI direct fills a bit more of the screen
The colour cast is slightly different
The HDMI output is brighter (a whole stop on the camera, but these shots were taken at the same settings). This is tweakable and might be partly down to the monitor settings for different inputs.
The VGA output seems slightly smoother. The direct HDMI seems almost to have slight ghosting on it
You can see the smoother output from VGA on this photo. Look at the circles.
Zoomed in photo of HDMI and VGA
Even though it’s slightly smaller, when looking at the whole screen, I slightly prefer the VGA output.
3) Old VGA monitor (1024 x 768)
Watching a video with Raspbian and Omxplayer (-o hdmi), on the small VGA monitor, I had no sound, so I tried OpenElec instead. The sound on that worked fine, but I needed to set the screen res to 1024 x 768 manually in OpenELEC to be able to see the whole picture. It’s a very old VGA monitor, but similar vintage to the school projector I want to use. The funny thing is that with my Samsung 23″ monitor, omxplayer played fine with sound.
So from this we know that the hardware all works fine, it’s just a question of making it work with the software. Quite likely, for school viewing, OpenElec will be a better proposition, as it’s more flexible about pause, skip, search etc and easier to resume. In fact, omxplayer on its own is not really user-friendly enough for that application. I often have to pause and rewind videos in class. Omxplayer quite often seems to exit when you try to navigate.
4) What about the projector?
So this week I finally managed to find a small slot of time, while I was in school, the ICT suite was free, and I could try out the converter on the ancient Epson projector. I used my Rev 2 Pi, an OpenELEC version from September 2012, the HDMI/VGA 1080 Ultimate video converter and some speakers. I had an .mp4 of Big Buck Bunny in full HD on a USB memory stick.
I had my phone with me, so I shot a couple of short clips of how it worked. In a word – perfect. As nice as Pi.
5) MHL adaptor, VGA monitor & Galaxy S2
Just for fun, I tried the adaptor with the old VGA monitor, some speakers, an MHL adaptor
MHL adaptor (micro USB to HDMI for phones)
and my phone (Galaxy S2). It worked a treat. The only issue was the need to put the phone in flight mode to avoid interrupted playback every time the cellphone network polls the phone.
Summing Up
This HDMI to VGA adaptor will do exactly what I bought it for, and it does it very well. £21 well spent – and it works with my phone too. I think any company that can find a way to sell something as good as this for £15 and still make a profit will absolutely clean up. It’s very good, but it’s just a bit too expensive to be a “must-have” Pi accessory. I’m very happy with mine though, and glad I bought it. I can now connect my Pi to virtually any TV or monitor in the world.
Alex Gibson, co-host of the Oxford Jam impressed us all with his RepRap 3d printer controlled by a Raspberry Pi. I hadn’t seen one of these up close and personal before. I’d really like one now, but I have a feeling it requires a large investment in time to build, calibrate and use. Check out the 4 minute video. Most impressive indeed!
Background
Alex told us he’d joined the Thames Valley build group, which is a bunch of people who get together to help each other make RepRaps. The reel of poly-lactic acid (PLA) costs about £30 GBP (~$50), weighs a kilo and can make loads of “stuff”. It takes a couple of minutes for the RepRap’s bed to warm up before it can start, then it took about 20 minutes to “print” the minimug. It’s controlled by a Pi, and Alex said it’s quite simple to install the required software on the Pi.
The Oxford Raspberry Jam
The Oxford Raspberry Jam seems to have an abundance of Peters and Alexes. This time three Peters, two Alexes and one Will exhibited. I didn’t get a record of them all, but they are well covered here and here.
I haven’t seen this documented anywhere either.
