The talk about the Acorn and RISC OS reminds me that I've been
interested in one of these, primarily to run RISC OS. What is the
recommended version, price, and place to get a Raspberry Pi from?
Over here Maplin sell a starter kit which they claim includes everything
you need. Well, it obviosuly doens't include a monitor. Nor does it
inlcude a case for the Rpi or any documentation. What it does include is
the Model B Rpi, USB hub, PSU, USB keyboard, USB mouse, WiFi dongle, SD
card with Rasbian and a couple of cables.
There are, IMHO, 3 thigns wrong with the Rpi. The hardwre, the software,
adn the docuemtnion.
The hardwae: I am not goign to maon about the USB ports. Or the HDMI
output. Or the fact that it's one partly-undocuemnted chip. I am goign to
moan abotu that GPIO port. It directly conencts to the ARM-thing. So if
you make a mistake, you wreck the Rpi. Logic signals are at 3.3V (not
suprisingly), but there's a 5V supply on tyhe GPIO connector, jsut
waiting to be shorted to the wrong thing byu a mis-wired cable.
Oh, and the GPIO port has nowhere near enough pins. You have a 2 wire
async port (TxD and RxD. SPI with a couple of CS lines. I2C. And 8 user
I/O lines which may not be a single 8 bit port (so there may not be
aquick way to send out a byte). ARGH!
What I would have done is to buffer the snync port to RS232 levels on the
board (lets face it, most people who want this port at all, wat RS23 2
levels). DO that with a _socketed_ MAX3232. BLow that up, jsut repalce
it. If you need a 3.3V async port, pop out the MAX3232 and put a jumper
array acorss the socket.
Then buffer the I2C port. bring that out, and also have a couple of
PCF8574s (8 bit I/O) and a PCF8591 (8 bit ADC/DAC) on the board. Again
socketed.
Yes it would be more expensive, but it might actually be useful
On a more generaly note, it looks a mess. There are a lot of bits to plug
together for the complete system. The board has conenctors all round it.
And it needs a case, there are SMD components on both sides of the PCB.
Software : Unless you have a fast internet connection that you can
connet the Rpi to, it's pretty much unusalbe. The suppleid Raspbian does
not include sources, and there is no obvious pointer as to where to get
them (since this is supposed to be an educational machine, it fails
spectacularly here). There are also all sorts of thigns misisng form the
standard distribution. YEs, you can install them, but. you ened the
internet conenction. It is possible to instal them from an USB mass
storage device (memory stick, etc), but while it's obviosu to those who
know debvian linux, it is not documented. Well, it is sort-of i passing,
but that documentation is wrong.
Docuemntation : What documentation? Yo uget a bit of paper telling you it
doens't meet the EMD directives (!) and a single sheet telling you how
to set it up. The latter is very incomplete. For a machien aimed at
beginners, there should be a set of instruciton of ghte form 'plug this
in here'. Look at the original BBC micro user guide.
There is a 3rd party user guide. It is a joke. For a achie nthat is
supposed ot teach programming, I would think the section on programming
should be rather logner than it is. And should mentuion things like
variables. Loops. Subroutines. ARGH!
There is no docuemtnation on msot of the linux commands. No problem for
us, but... In particular, there is no docuemtned way to back up the OS.
Yes, you can connect a USB card readeer, put in another SD card, and dd
it over. Fine if you know how to use dd. Not fine if you don't. Again,
there needs ot be a specific set of instructions on how to do this.
Especially as it's all too easy to mis-configure the machien so it won't
boot.
-tony