26 Feb
2013
26 Feb
'13
5:25 p.m.
On Mon, Feb 25, 2013 at 10:45:50PM +0000, Tony Duell wrote:
Wait. They squeezed every _cent_ from the BOM and you are surprised that
the results are less than ... impressive?
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
Yes, that information was cleverly hidden at:
http://www.raspbian.org/RaspbianFAQ
or, for just the package sources:
http://www.raspbian.org/RaspbianRepository
and:
https://github.com/raspberrypi
has the kernel and various other bits. Yes, the GPU specific code is
still binary only - you can thank Broadcom for that.
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.
The packages you consider important and the packages that I consider important
and finally those that anybody else considers important probably don't have
that much overlap. What should they do? Install the world and require a
32 GB SD-Card (guessing on the size here). Offer a 16 GB download (compressed)
for the "base image"? Similiarly for not including source in the standard
image. The checked out kernel tree alone is several hundred MB.
The size of the full download for Debian armhf testing (what Raspbian is
based on) is a full DVD image with 4.3 GB. And that presumably has only te
binaries as _compressed_ archives.
Shipping _everything_ (complete binary & source distro) to _everyone_
who buys a Raspberry Pi would increase the price a quite a bit. Lets
say we only need a 16 GB sd-card: that is another USD 15 right there and
most people won't need it.
So: you can easily get the stuff, but it needs an Internet connection.
Big deal. So complete and test your Raspberry Pi setup before you wander
off in the woods where there is no network connection ;-)
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.
People seem to mistake the Raspberry Pi as the second coming of the BBC Micro.
It assuredly isn't.
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,
The Internet exists. So does Google. Seriously.
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.
And that is one key thing they got right with the Raspberry: if it doesn't
boot, you swap the SD card and you're done. No need to hunt down the JTAG
gear.
Kind regards,
Alex.
--
"Opportunity is missed by most people because it is dressed in overalls and
looks like work." -- Thomas A. Edison