So one day I got home to find a package from premier farnell waiting for me. Yep, it was a mbed dev board.After playing around with it for a while, I started to write a review only to lost it due to a bluescreen 
Since a lot of other people have written excellent reviews for the mbed, I'll try to write about things that are not yet covered (though after re-reading this I think I went into random rant mode instead... whoops).
Since a lot of other people have written excellent reviews for the mbed, I'll try to write about things that are not yet covered (though after re-reading this I think I went into random rant mode instead... whoops).First, how it looks! For those who are curious, the mbed comes in a small box with a bunch of stuff inside; see the photo below:
One thing I especially like is how they give a very nice reference card with all the pinout functions of the board in it. I'm not sure why there's two in the box - a paper card and a plastic card, completely identical. I also liked how it comes with a VERY long USB cable - over 1.7 m in length. I'm using a laptop myself but I can see this being very useful for people who are using desktops that are tucked under their desk, in the cupboard etc. It's probably a bit too stiff to be used as a tethering cable though, in case you want to make a robot with it. The paper on the top left is the quick start guide, while the circular thing in the center is a sticker (which now resides on my luggage)
There are some not-completely-filled-in solder pads, but they are on the USB port mounting holes, so that's tolerable. The rest of the board have nice soldering job on them. The mbed includes ethernet PHY chip, so ethernet projects only require a set of magnetics and the jack to get going. The board is clearly designed for prototyping with a breadboard with the presoldered pins. There's two micros on board: the main LPC1768 (which is pretty beefy as far as microcontrollers go) and a mbed magic chip (which provides the USB connectivity, flash drive interface, serial, and all the nice other things). The board have output power from the onboard regulators (to power small prototype circuits while developing) and also a pin for input power (when you finish development and now leaving it standalone).
I really like how easy it is to get started with the mbed - you plug it in, it will show up as a usb drive with a html file. Clicking takes you to their 1-step registration page, and you're ready to start working. I'm not sure what will happen if you accidentaly erased the file, either before or after registration so it might be a good idea to back it up somewhere.
Now one of the most distinctive feature of the mbed is the online compiler, so I neglected the getting started guide for now and dived straight in. I was expecting some kind of slow, heavy full featured interface, so imagine my surprise when the IDE loads up quickly (at least faster than my Gmail). It is also very responsive and light - I like it. You can directly import other people's published projects from the interface, though it shows up as a single massive unwieldy list. In my case the very first program was a Knight Rider style flashing LED, and after a few clicks I have moving lights in my room.
Speaking of the 4 available LEDs, they are definitely some of the brightest surface mount blue LEDs I have ever seen. It's clearly visible from across my room and is actually disturbing me when I work. A piece of masking tape solves the problem easily though. I suppose it would be great for people who like to work in daylight or out in the field, but it's a tad too bright for indoor use. I think I read someone commenting that the LEDs should be different colors to help distinguish them easily. Fair point, but my knight rider lights won't look as cool in three different colors that way, so I'm fine with the current setup :)
Now back to the compiler, it allows you to work from multiple computers, and not need to deal with installing any toolchain which can be tricky. This also means that they only need to target a single platform (javascript) rather then different OSes. (Ok, there might be some browser-specific code, but you get the point.) If anyone wonders the back-end is the ARM realview compiler.
For those who want to work without internet connection, I heard that some people are experimenting with using normal toolchains (the one you need to install on your computer) with considerable success. Personally I liked how the mbed was designed - all the magic happens on a separate chip leaving the LPC1768FBD100,551LPC1768FBD100,551 empty, which means you can put any valid code in it, no matter who compiles it and it will still work.
One thing that annoys me however, is that the online compiler does not seem to have any sort of version control built in. This can get really annoying if you're not careful with your code. Considering that debugging through JTAG is not available, you're left with serial output and flashy LEDs. (and for anyone curious, this is because JTAG is used as part of the magic that happens when programming the device).
Another thing unique to the mbed is their so-called mbed library. These provides functions to interface with the LPC1768FBD100,551LPC1768FBD100,551 peripherals easily without having to deal with the super low level stuff, changing registers, etc. I have not yet played with them, so I can't comment on them so much except that other people who uses it seems to be satisfied. Hmm, now I wonder if you can still write pure low level code with the online compiler without the library. Oh, and they're written in C++ if anyone wonders. The libraries are closed source, though they say they'll open it up in the future but not before active development is over. Now this is just a wild guess, but I had a feeling that this might be an effort to extend the CMSIS project (which is basically a standard for interfacing with lowlevel registers to help code re-use).
Finally, the mbed website has to be given some credit. They went as far as creating a tool for people to discuss and share their project easily. There are quite a fair bit of documentation present, and from what I've seen the mbed people also participated a lot in the forums (you actually need to buy an mbed to be able to register and post there, so the signal to noise ratio is pretty high). Again, I haven't had much experience with them, but for now it seems good!
Now I read some of the latest emails, and I was wondering if I should try to find some project to test my mbed with. Then lo and behold, it just happens that my friend is going to do an electronic design course, and needs some sort of development platform - and hey, I do have one here! So instead of idling on the shelf, my mbed is now on a long-term loan. I may or may not post updates though, depending on workload :(
So to summarize:
The good things:
- Online compiler means no hassle in installing toolchains.
- mbed library makes it easy to get interfaces / peripherals up and running
- Ethernet PHY on board
- Board still usable even if you decide not to use the online compiler / mbed library
Things I don't like:
- Online compiler means no compiling without internet connection
- No revision control on the online compiler
- No access to JTAG port - though only if you need one.
- Mbed library is closed source
- Blinding LEDs
Thoughts? Comments?
(my line breaks somehow got eaten by the editor... why?)
