Resurrecting Wacom's ADB-connected Intuos Tablets

Bloody hell. This has been the work, on and off, of over a decade. An ongoing thing that I'd prod at from time to time, a "let's have a look at that sodding thing again" project. Proof, if any were needed, that I'm persistent bastard, and that once something gets under my skin, it stays there.

I've no idea what I'm gonna do now. Because it works. I currently have my (originally) adb-connected Y2k-era intuos hooked up, via USB, to my modern Mac running Mavericks.

Enough blathering.

https://github.com/tufty/adb-intuos

I wouldn't have got this far if it wasn't for the work done by Bernard Poulin, both
on the waxbee project, and the help he's given me in figuring out what the
packet stream means.

The technical requirements are (apart from an ADB Intuos) identical to those for
Bernard's waxbee converter, even down to the pins used for the ADB connection on
the Teensy. There's reasons for that, most of which boil down to me "borrowing"
Bernard's ADB codec code. In any case, if you already have a Teensy wired up for
an Intuos in the vague hope someone would eventually make the damned thing work,
you're good to go. If you haven't, get one and wire it up.

What does this do?

It converts an ADB intuos tablet into the equivalent sized USB-equipped Intuos 2,
thus enabling the use of stock Wacom drivers (up to v6.20, the last version handling
Intuos 2 tablets; this may preclude being able to use the tablet on Windows Cool
on your computer.

I like the sound of that. What does it handle?

I *believe* it handles all ADB intuos tablets without any need for configuration.
It certainly handles the features of my GD-0608-A, including dual tracking, button
bar, standard pen and 4D mouse.

Sounds ace. What's the catch?

It *certainly* doesn't handle any other tools. That's because I don't have any of
them, so I can't work out how they work. Yes, that /is/ a hint. Please contact me
if you have other Intuos 1 tools you can either lend me (I'm in France) or can
hook up to an ADB intuos and dump the output.

How do I make it work?

Get yourself a Teensy 2.0 from pjrc.com
Wire it up : https://code.google.com/p/waxbee/wiki/InterfacingADB
Get yourself an AVR toolset. The rest is based on having a command line toolset and some sort of *n*x. Got a Windows? I have no idea what you do.
Get the code : git clone https://github.com/tufty/adb-intuos.git
Go to the 'converter' subdirectory, and type 'make'
Load the resulting intuos_converter.hex onto your teensy using pjrc's teensy loader
Unplug and replug the teensy, and you're off

going back to snow leopard from mavericks

So, like a moron, I decided to upgrade my 2008 24" iMac from snow leopard to Mavericks. After all, Apple's updates make shit run faster (or, at least, have done in the past, and I've been doing OSX since the DP). Step one was to go to Mountain Lion. 29 bucks later, I had a mac that ran like shit. So, get myself 4GB of memory, find one chip is dead (the dangers of second user memory). and a 3GB mac that sorta ran acceptably. hrm. Mavericks, then. A fuxking huge download and install, and, again, a mac. that runs like shit. Beachball frenzy. Of course, this is the point at which my time machine disk decides to die. Now, my time machine disk is not formatted as a single volume, but has a bunch of extra stuff on a now inaccessible volume. Crap. time to pull out ddrescue, at least to recover that extra stuff. ddrescue is the number 1 go-to tool for recoveribg data, it's free, and I can't recommend it highly enough. It took 7 passes to do its thing, but I have my data back. Next up is to try and get my external disk to come back to life. More ddrescue, copying /dev/zero to the freshly partitioned disk. 750gb takes a bit of time, good job I'm off work with a sciatica (2 injections ov valium & profenid per day, makes life more or less tolerable). I will, of course, blame spalling pisstakes, grandmatikal erorz and other crap on being drugged out of my tiny box, as well as entering this on an iphone's poxy osk. next step. export contacts and diary entries from Mavericks. then clone the internal disk to the external drive, and disconnect the fucker. Boot 10.5 from the original disks (my 10.6 DVD won't even boot with Mavericks installed) and reformat the internal disk to zero. Install 10.5 and restore the 'original' extras, upgrade to 10.6, then manually restore all my data from the external drive (importing the stuff Mavericks has shat all over). And then. Recompiling my 5 cross-deveopment toolkits. yes, I'm a happy bunny. Not

Atomic setting on ARM

Back to our scheduled programming.  Big gobs of ugly assembly code.

When implementing a multitasking operating system, there is a need for dealing with mutating shared state.  It's one of the unpleasant realities of the world of multitasking (and, indeed, multithreading), and it's fraught with danger.

One of the basic functions we need to implement is the "atomic set" operation - setting a variable to a given value.

Let's take the example of incrementing a variable.  Naively, we might do this:

    ldr r0, [r1]
    add r0, r0, #1
    str r0, [r1]


In most cases, this will work.  However, there exists a case where, in fact, this can fail - if two threads of execution are trying to increment the value, and a task swap happens whilst one is actually doing the increment, the possibility is that the value will be (incorrectly) incremented only once, as follows:

; Assume r1 points at a given address, holding the value 0
[thread 1]
    ldr r0, [r1]  ; r0 in thread 1 is now 0

[thread 2]
    ldr r0, [r1] ; r0 in thread 2 is now 0
    add r0, r0, #1 ; r0 in thread 2 is now 1
    str r0, [r1] ; memory is now 1
...

[thread 1]
    add r0, r0, #1 ; r0 in thread 1 is now 1
    str r0, [r1] ; memory is now 1


Obviously, we would expect memory to be set to 2, not to 1.  So somehow we need to either stop the interrupts happening (easy enough, turn interrupts off, but that has fairly big impacts elsewhere) or somehow deal with the case where we are interrupted mid-operation.

As luck would have it, ARMv6 provides us with 3 handy opcodes for this : ldrex, strex and clrex.  Basically, we use ldrex to signal that we want to have exclusive write access to a memory location, strex signals that we're going to write to a location and close that exclusive access, with a test for success, and clrex says "hey, we're no longer interested".  So, how do we use these to do what we want?

Let's go back to our example above - incrementing a value in memory.  Using ldrex / strex it would look like this:
try_increment:
    ldrex r0, [r1]
    add r0, r0, #1
    strex r2, r0, r1
    cmp r2, #0
    bne try_increment

What happens here is:

• the initial ldrex loads the memory, and indicates that it wants an exclusive access to the memory itself.
• We then increment our value, as usual.
• We write the value back using strex - this will only succeed if:

1. we still have an exclusive lock on the memory
2. no newer writes to that memory have happened since we established our exclusive lock

• success of strex is indicated by register r2 (the "extra" operand that strex uses) being set to 0.
• If strex has failed, we go back and try again from the point where we loaded the initial value.

For our super-simple increment case, this will probably catch 99.99% of cases.  We add a "belt-and-braces" approach, however, by making our task scheduler explicitly invalidate all exclusive reads, using the clrex opcode.  This has the possibility of making any in-process ldrex-strex blocks restart (and thus take more time), but covers all the bases.

Now, that's all fine and well, but we may want to use this method in our C code, without resorting to subroutine calls (by their very nature, exclusive operations happen at a very low level, and probably want to be inlined).  So we're going to want to use some of that nastiest of nasties, inline assembler in gcc.  Believe me, it's vile.

Here's an implementation of an inline atomic increment using gcc inline assembler:
inline uint32_t atomic_increment(uint32_t * memory) {
  uint32_t temp1, temp2;
  __asm__ __volatile__ (
    "1:\n"
    "\tldrex\t%[t1],[%[m]]\n"
    "\tadd\t%[t1],%[t1],#1\n"
    "\tstrex\t%[t2],%[t1],[%[m]]\n"
    "\tcmp\t%[t2],#0\n"
    "\tbne\t1b"
    : [t1] "=&r" (temp1), [t2] "=&r" (temp2)
    : [m] "r" (memory)
  );
  return temp1;
}


Horrible, no?  Note the use of local labels ('1:' and then branching to '1b' to indicate the latest local label called '1'), having to use encoded tabs and newlines to stop the assembler itself barfing, and the horrible workaround of multiple names for the same variables because gcc is, quite simply, broken.  Still, it works, and the C optimiser can deal with it.


If you want to get more complex, I'd suggest looking at the ARM site for the example implementations of mutexes and condition variables using ldrex/strex.  You'll have to deal with converting from ARM assembler to GNU, but as long as you don't try inlining them, you should be fine.

An aside. Vector maths for games

Most people, when they start writing games, run up against having to rotate and move objects.  Generally speaking, they attack this problem "head on" using using trigonometry, specifically using sines, cosines and arctangents.  This is a direct application of the SOH/CAH/TOA trigonometry you learned (or are in the process of learning, or will be learning later on) at secondary school.

Although simple and easy to understand, this approach has a few drawbacks.

• The first (and usually most noticeable) of these is that it's quite slow.  It's manageable for a small amount of objects, but if, for example, you're trying to do something like "Geometry Wars" with thousands of objects rotating and moving at the same time, you're soon going to find that all the trig rapidly becomes a bit of a bottleneck.  It gets even worse if you move into 3 dimensions.
• The second is related to the first, and, in these days where GPU acceleration and multi-core processing are commonplace, can be a major sticking point - Trigonometry can be hard to efficiently parallelise.
• The third, and perhaps most important despite being the least obvious, is accuracy.  Floating point calculations are never exact, and the errors in a purely trigonometric approach are usually cumulative.  Generally speaking, this means that if you rotate an object by 1° clockwise, 360 times, it will not end up where it started.

Luckily, there exists a way to almost totally bypass the trigonometry.  Let's recap what state we usually end up using for an object.

• We keep track of its location in space.  We typically do this using a pair of co-ordinates.
• We keep track of the direction it's facing.  Typically using an angle.
• We keep track of the direction in which it is moving, again using an angle.
• We keep track of its current speed.

We also know how to convert from cartesian co-ordinates (x and y) to polar coordinates (angle and size) and vice versa, we know that polar co-ordinates are equivalent to cartesian co-ordinates, and we've seen that, for some tasks, it's easier to use polar co-ordinates than cartesian ones.

What we're going to do is get rid of all the references to angles, and all the trigonometry.  We're going to do this by using vector mathematics.

So, we have location.  This is a set of co-ordinates, and thus a vector. So far, so good.

By combining direction of movement and speed into a single conceptual value, we get velocity, which is a set of (polar) co-ordinates, and also a vector.  Unfortunately, it has an angle embedded in it, but as we know that polar and cartesian co-ordinates are equivalent, we can represent it in cartesian form (velocity-x and velocity-y).

Which leaves us with that unfortunate direction we're facing, which is a single value indicating angle, and thus a scalar.  However, the only bit we're interested in is the angle, so we can convert it into a vector with a size of 1 (a unit vector), and then get rid of the 'angle' part by converting it to cartesian form (facing-x and facing-y).

So what does that get us?

Well, let's look at the tasks we have done so far.

Moving an object from its current location to the next location

This is the most basic task we want to do, and it's also the most simple.  It's a trivial vector addition of location and velocity, which is to say :

location-x = location-x + velocity-x
location-y = location-y + velocity-y

Accelerating an object in a particular direction

Again, this is pretty simple.  We represent the acceleration as a vector quantity, and add it to velocity :

velocity-x = velocity-x + acceleration-x
velocity-y = velocity-y + acceleration-y

That's the basics of acceleration, but how do we get the acceleration value?

I'm going to explain a basic model of Newtonian physics.  Newton's Second Law is most commonly stated as *F=ma*, where F is the force applied to an object, m is its mass, and a is the acceleration - it can be restated as *a=F/m*.  So to calculate the acceleration of each object, we need to know the force acting on it, and its mass.

We'll assume the mass of the object is constant, for the moment (no near-light-speed effects here, thank you), so what wee need to calculate is the force acting on the object.  Force is a vector value, and the overall force acting on the object is simply the addition of all the forces acting on it.  So, we'll start each "step" of the game with a clean slate, and add the forces up as we go:

force-x = 0
force-y = 0

... Accumulate forces

acceleration-x = force-x / mass
acceleration-y = force-y / mass

So, let's look at the common forces we might

"Thrusting"

To apply a "thrust" in the direction we're facing, we can use the unit vector *facing*, multiplied by some constant of "thrust strength", as follows (remember, *facing* is a unit vector, so it always has a length of 1) :

force-x += facing-x * thrust-strength
force-y += facing-y * thrust-strength

Acceleration towards the floor due to gravity

Assuming that gravity always works downwards, and that our co-ordinate system starts at the bottom left, we can make gravity work as follows (obviously, the value of gravity-constant should be chosen to work with whatever system of units we're using):

force-y -= gravity-constant

Acceleration towards (or away from) other objects

There's 2 cases here.

The first is a very simplistic "chasing" behaviour, where an object "chases" another one.  This is usually best done by rotating the object to point at its target (see later) and then "thrusting" as above, but it can also be useful to carry out a simple "go that way" approach.

The second is a more complex simulation of gravity - if we were implementing something like Geometry Wars, we might have "black holes" that pull objects towards them.  In this case, gravity is a bit more complex, as it not only works in a different direction for each pair of objects, but it gets stronger depending on how close the objects are to each other.

In both cases, the first thing we do is to create a vector that gives both the direction in which we are going to be pulled, and the distance between the objects:

vector-x = other.location-x - location-x
vector-y = other.location-y - location-y

In both cases, we need to know the distance between the two objects.  For the simple chasing case, we'll calculate it directly:

distance = size(vector)

Now, gravity usually works according to what's known as an inverse square law, which is to say that it's inversely proportional to the square of the distance between the two objects.

Remember, Pythagorus tells us that, for any right angled triangle, the sum of the squares on the short sides are equal to the square on the hypotenuse - the square on the hypotenuse is, in this case, equal to the distance squared, so rather that calculating the distance in a single step, we do it in 2 steps so that we can keep the "distance-squared" value :

distance-squared = (vector.x * vector.x) + (vector.y * vector.y)
distance = sqrt(distance)

Now, in both cases, we want to scale the vector by a factor.  To do this, we need to scale the vector to a unit size, and then multiply it by our factor.  To scale to a unit size, we divide each co-ordinate by "distance" :

vector-x = vector-x / distance
vector-y = vector-y / distance

For the simple chasing case, we now multiply by our "chasing strength", and we have our force :

force-x = vector-x * chase-strength
force-y = vector-y * chase-strength

For the attraction due to gravity case, we divide by the distance squared, and then multiply by some constant to get a usable value :

force-x = (vector-x * gravity-constant) / distance-squared
force-y = (vector-y * gravity-constant) / distance-squared

Braking / Friction

Braking is a special case.  We could implement it by making a force vector that points in the opposite direction to the current velocity, but it's simpler (and faster) to simply multiply the current velocity by a factor.

"Proportional" braking is very simple.  If we wanted, for example, to brake by 5% every "step", we would do this:

braking-factor = 0.95
velocity-x = velocity-x * 0.95
velocity-y = velocity-y * 0.95

This makes a very realistic simulation of friction.

"Fixed amount" braking is a tiny bit more tricky - we need to know the size of the current velocity (using Pythagoras' theorem) and work out the factor from there:

speed = size(velocity)
if speed < braking-amount
braking-factor = 0
else
braking-factor = (speed - braking-amount) / speed
endif
velocity-x = (velocity-x * braking-factor)
velocity-y = (velocity-y * braking-factor)

Rotating

Now, so far, everything we've done is incredibly simple - the most complex thing we've come across is a square root, and we haven't had to bother with angles *at all*.

Rotating objects is a bit more complex.  After all, how can we rotate something to a given angle if we don't know what angle it's already at?

The short answer to this is

 I lied.  It's not complex at all.

but the short answer isn't very interesting (and, above all, doesn't tell us anything useful).  The long answer follows, and is based on matrix multiplication.  As a reminder (or a first taste, if you've never seen this before), a matrix is a (conceptually) rectangular grid of values.

Given that we're dealing with 2 dimensions, one of the most useful matrices we can imagine is a 2 x 2 matrix; we can multiply a vector (x, y) by such a matrix as follows :

| a b | |x| = |(x * a) + (y * b)|
| c d | |y|   |(x * c) + (y * d)|

Now, that's pretty simple to understand, and it's trivially simple to implement in code. So, multiplying a matrix by a vector is going to return a vector with (potentially) different values, depending on what's in the matrix. So far, so good, right?

Now, let's go back to rotating stuff using SOHCAHTOA, keeping that in mind.  When we rotate a point (x, y) by an angle θ, we get a point whose x co-ordinate is given by (x * cos(θ)) - (y * sin(θ)), and whose y co-ordinate is given by (x * sin(θ)) + (y * cos(θ)).  Now that looks a lot like the matrix multiplication above, and indeed it is.  We can encode a rotation by some arbitrary angle θ as a matrix, as follows:

| cos θ -sin θ |
| sin θ  cos θ |

This is, in fact so useful that the majority of graphical toolkits (OpenGL, DirectX and so on) provide an API that uses matrices (actually, an extension of the rotation vector given above, but we'll see that later)

Now that in itself is pretty nifty, but here's where the real magick occurs.  Remember SOHCAHTOA?  Remember what it means?

• Sin of angle = length of Opposite / length of Hypotenuse
• Cos of angle = length of Adjacent / length of Hypotenuse
• Tan of angle = length of Opposite / length of Adjacent

We've already used the TOA bit, when we used atan2 beforehand.  We're about to use the SOH and CAH bits to our profit.

Consider a unit vector. The length of its hypotenuse will always be 1.  And as any number divided by 1 is unchanged, we can see that the sin of the angle of that vector is given by the length of the opposite and the cos of the angle of that vector is given by the length of the adjacent.  And we know those values already - they are, quite simply, the co-ordinates of the vector.

So, rather than talking about angles, we can talk about unit vectors, and do away with all that messy trigonometry.  Well, at least when we're talking about taking something that's aligned at an angle of zero, and rotating it to a particular angle as described by a unit vector v - we use a rotation matrix like this:

| v.x -v.y |
| v.y  v.x |

giving us

new-x = v.x * x - v.y * y
new-y = v.y * x + v.x * y

What does this mean?

• We can, using our handy unit "facing" vector, draw a graphic of our object, rotated to the correct angle, without having to call any trigonometric functions whatsoever.
• We can make an object A point at another object B by calculating the vector A->B (trivial, this is given by B.location - A.location) and then scaling it to unit size (again, pretty easy - divide each coordinate by the length of the original vector), and using that as the new "facing" vector for object A.
• If we need "increment" or "decrement" ability (for example, "rotate by 5° CCW") we can precalculate unit vectors describing the angles we need (obviously, this would need to be done using trigonometric functions, but it would only need to be done once), and then use those vectors to create our rotation matrices.

The only thing that's really left is rotating one object rotate towards another (think turret slowly rotating to face player) in increments.  To do this we need to know whether we are going to rotate clockwise or anticlockwise.  The easiest (although probably not the fastest) way to do this is to use atan2() to get the angles of the current "facing" vector and the vector A->B, to decide which way to rotate, and then use the incremental approach above.

Earlier, I touched on the fact that the various toolkits all provide matrix APIs.  How these work is by combining both a rotation and translation matrix (yes, we can deal with translations too) into one matrix.  For a 2-d case, we would do something like this:

|  cosθ -sinθ  t.x  |   | x |
|  sinθ  cosθ  t.y  | * | y |
|   0     0     1   |   | 1 |

Ignoring the pointless result given by the 1 in the vector, we would get :

x = (x * cosθ) - (y * sinθ) + t.x
y = (x * sinθ) + (y * cosθ) + t.y

This is, simply put, the value we had before, with the x and y values of t added on.  The matrix therefore rotates an object by *θ*, and then translates the result by *t*.

The matrices used by OpenGL and so on are not, in fact, 2D specific.  Everything is generalised to the 3D case, so we use :

|  cosθ -sinθ   0    t.x  |
|  sinθ  cosθ   0    t.y  |
|   0     0     1     0   |
|   0     0     0     1   |

This is actually a matrix for 3D translations and rotations, with all the z axis stuff left out.

Back to Tech : Building for ARM "on the metal"

It's been a while since I posted anything technical, what with the winter season and moaning about the launch of the Pi, price gouging on ebay, playing hockey, teaching my 12 year old to program, and a whole  load of other stuff.  Fear not, though; LambdaPi is still moving onwards, I have a branch on my machine that separates everything that is Lisp from everything that is kernel, and is moving towards a more solidly real-time base.

Anyway.  I had a request from Angus Hammond asking about build scripts, as follows:

Would you be able to do a blog post at some point explaining how the build script you use in lambdapi works? The linking needed for an OS is obviously different to that needed normally if only because of the interrupts table, and that script is completely beyond my understanding. It would be greatly appreciated if you could explain any of the working behind it.

The answer to this is, of course, "of course".  So let's have a look at what's required.

Firstly, we need to understand what we want.  The way the Pi boots (and the way I'm using qemu) is to (eventually) load a binary image into memory at location 0x00000000.  This binary image is required to start with a standard ARM vector table, which we have already seen.  Execution actually starts by transferring control to the ARM with the PC set to 0x00000000, the standard "reset" vector.

So, what's going on in the build process?

Well, firstly, we compile and assemble everything we need into object files.  So far, so standard.  The tricky bits come with the following Makefile rules :

bin/kernel.img: bin/kernel.elf
  ${OBJCOPY} -O binary $< $@

bin/kernel.elf: lambdapi.ld $(OBJ) $(SYSLIBS)
  ${LD} ${LDFLAGS} -T lambdapi.ld $(OBJ) $(SYSLIBS) -o $@


The first of these to be executed is the one that builds bin/kernel.elf - this is dependent on the link script lambdapi.ld, all the object files $(OBJ), and all the assorted libraries we're using $(SYSLIBS).  We call the linker ${LD} with a set of flags ${LDFLAGS}, using a linker script lambdapi.ld, passing in all the object files and system libraries.  LDFLAGS are set to 

-nostdlib -static --error-unresolved-symbols



Which means "don't try and link any standard libraries, link everything statically, and throw an error if there's anything you can't find".  

So, at the end of that step, we should have a properly formatted elf-format file.  Unfortunately, that's not what we want, we need to lose all the elf stuff and end up with a raw image to be loaded at a particular location, hence the objcopy stage, which takes the binary bit of the elf image and spits it out, standalone.

Now, all we need to know is how to make the linker file.  A standard ld script takes a bunch of object files and munges them all together, keeping the .text (code) sections together, then appending a load of other stuff at the end, notably the bss and data sections.  Unfortunately, it doesn't guarantee any particular order of entry, and we *need* our reset table to be the very first entry.  So, we need a custom link script.  Let's look at it.

ENTRY(__reset)
SECTIONS
{
. = 0x0;
.text : {
*(.reset)
*(.text)
}

__exidx_start = .;
.ARM.exidx   : { *(.ARM.exidx* .gnu.linkonce.armexidx.*) }
__exidx_end = .;

.data : { *(.data) }
__bss_start__ = .;
.bss : { *(.bss) }
__bss_end__ = .;
}


The first thing we do is tell the linker where the entry point is : symbol __reset.  In reality, we only need this if we'll ever be using the elf file directly, which we won't, but it doesn't hurt.

Now for the meat of the script.  We start by setting the link location to be 0x0, and then we create a text (code) section.  The first part of this will be the vector table, which we have handily tagged in vector_table.s with a .section directive as follows:

.section .reset, "ax"

This tells the assembler that the code assembled should be placed in a section of code with a name of  .reset (which I made up, I could equally well have used .simon, .foo, or anything else, as long as I was consistent between the ld script and the section name in the code itself).

In fact, we're linking all code labeled with a .reset section name first, but as there's only one of these, we can guarantee it will be first.

After that, and still within the .text section, comes anything linked as .text.  Basically, that's everything "code" spat out of the C compiler, along with everything else we've labelled as code in the assembler.

Then we have a .ARM.exidx section, that's required for C++ exception handling if we ever need it.  We don't, at the moment, but might do later.

Then we have the .data section - that's for any pre-defined, read-only values.

And finally, we have the .bss section - space allocated for unassigned data we might write to.

You'll also note that we set a couple of variables, __bss_start__ and __bss_end__ to the current link location "." - these are referred to in the code (so that we know where bss starts and ends, and thus where free memory starts) and will be replaced by the linker with the correct values.

And that's pretty much it.  It looks scary, but it's not.

If you want chapter and verse on this, check out this article which is much more explicit, and covers using system libraries and so on.  Also, it's worth looking at balau's blog entry on newlib (and all of balau's other bare metal articles, which are highly instructive).  And, of course, the gnu binutils documentation.

Simon

Radio silence and gouging (A follow-up to Black Piday)

It seems that the raspberrypi.org forums are back up, and have been for 12 hours or so.  So far, there's only 2 people on the forums who seem to have got confirmed orders for Pis from the first batch.  Given that there were upwards of 12K people registered on the forum, and most of them were probably frantically trying to get orders in from 06:01 on the 1st, we can safely say that demand was "underestimated".

Oddly, there seems to be very little spleen being vented towards the Foundation, but some not inconsiderable anger directed at Farnell and RS, mainly over their incompetent and inconsistent handling of ordering and preordering.  This anger is, I believe, misplaced - there's far more wrong with what RS (to a lesser extent) and Farnell are doing than being simply incompetent.

I'll say it now.  I feel that handing over control to Farnell and RS was a massive mistake, and it may cost the foundation much of the goodwill they have accumulated even whilst they were missing their hoped-for delivery dates.

RS are seemingly not acknowledging anything.  Nobody is reporting any response at all from them.  "Register interest" and - nothing, nada, que chi.

Farnell are, logistically speaking, doing better - they (if you can find the link to order in your country) are accepting preorders.  However, they are:

• Giving wildly optimistic delivery dates on order, which are then being modified in email
• Advertising and confirming orders at one price, and then subsequently modifying the price (which, as far as I understand it, but IANAL, is contrary to the Sale of Goods Act, at least in the UK)
• Selling the Pi at inflated prices.  This is the worst, as the price point was the one thing the Foundation have stuck to, and was a major selling point. The Model B (which is all that's on "sale" at the moment) was supposed to be 35 USD plus locally applicable taxes.  In France (and, I believe, the rest of Europe), Farnell are quoting 33.07 EUR before tax, which comes to 42.65 USD.  That's a 21% markup.  The UK gets an advertised 24.65 GBP, or 39.03 USD, but a reportedly subsequently modified price of 26.65 GBP, or 42.20 USD.  Again, a >20% markup.

I cannot understand why the Foundation are allowing this.  RS are advertising at 21.60 GBP, which is, at least, at the 35 USD price point.

Farnell are destroying the Foundation's year-long commitment to a given price point.  The Foundation should pull their licence NOW.

It has been pointed out that, in their defence, Farnell are merely rolling the shipping cost into the purchase price and shipping for free, but that's actually fairly dishonest - it's a "reverse eBay" (i.e. the reverse of the situation where an article is listed with a low price and then the rest is made up by gouging the shipping).  If you were (able) to order more Pis than one, you effectively pay for single item shipping on each and every one (or, put simply, overpay your shipping cost massively).

Black Piday

So, I didn't get a Raspberry Pi.  I'm not feeling overly bitter about it, as I wasn't actually expecting to, if nothing else because I was already at work before the 6AM GMT deadline. What I am mildly miffed about is that I can't currently do anything other than "express an interest in buying one" (or, in supplier-speak, "become a mailing list asset") from the major suppliers.  I've had an interest since May last year.

As I type this, the Raspberry Pi site is still showing a static page.  There's no official news about what happened, who got one, who didn't, what the details of the deal with Farnell and RS are, apart from Twitter.  The unofficial news (i.e. the stuff in print) is almost all wrong in fundamental details.

I wouldn't want to have been one of the inhabitants of #1 Fruity Loop recently. It was becoming increasingly evident that there was no way 10,000 Pis were going to suffice.  With every hour, new "news sites" were picking up on the Pi as a "$25 computer that does XBMC". None of them were picking up on the actual goal of the Pi itself, or mentioning the limitations of the Pi as an XBMC machine, or even any of the actual hardware features of the Pi beyond "it does XBMC". The wave upon wave of new users descending on the Pi forums and asking if they can install Windows on the Pi bore witness to this. What had started as a dream was rapidly becoming a monster. It was totally out of control, and there was no way the foundation would ever be able to meet the demand.  Hence, I guess, the throwing up of hands and handing control of the hardware delivery side of things to a pair of corporate rapists[1]

When people start realising what the limitations of the Pi as an XBMC machine is, the nerd rage will be spectacular.  We probably have a week or so before they start being delivered to homes around the globe, and the "this thing's a fucking pile of shit" threads on the already overloaded forums start sprouting up by the thousand.

The foundation themselves are largely to blame for this turn of events, as recent news has all been about multimedia and XBMC, and nothing to do with education at all.  Indeed, the "About Us" page on the Raspberry Pi site has been changed from a short and sweet statement of the goals of the foundation into a bunch of word salad.  From being about teaching programming, it's suddenly become

We want owning a truly personal computer to be normal for children.

So, when 6AM GMT ran around, Farnell, RS and Raspberry Pi.org went down simultaneously. Not taken down by wave upon wave of pent up demand for educational computers, but by scalpers and people from hotukdeals.co.uk. These are not people who are going to do educational projects with the board, they are going to stick them to the back of the telly with blu-tac. the foundation wanted "the community" to take the board and supplied software, run with it, and create interesting projects.  Installing XBMC is no more interesting in terms of computer science than editing a document in Microsoft Word, the kind of crap that's being taught in ICT, the kind of thing the Raspberry Pi was suposed to fix.

None of the people I know who are planning educational projects managed to get one from the first batch. Only one of them managed to get a preorder rather than "expressing an interest".

There are probably less than a hundred people on the forums who are planning interesting stuff.  putting aside 1% of the first batch "for them", even if it was done behind the scenes, would have done far more for the foundation's erstwhile goals than selling a million Pis to people who want to make Mame machines and set top boxes.

So, like I said, I'm not bitter.  But I am fucking angry.  The emphasis has gone from producing something important, i.e. a machine that helps in teaching kids (and adults) how to actually control the hardware they own, on to simply producing another gadget.  That emphasis has been changing slowly since around December.  The sale itself was a total fucking mess, and, it appears, fucked up by both the foundation (setting a solid date and time for server meltdown, days in advance, and thus further engorging the until-then self-sustaining hype machine, was never gonna be a good idea), and RS/Farnell, by all accounts, don't appear to have been even close to ready (from denying the existence of the Pi through to stating that they will only be available to resellers).

I remain totally committed to the originally stated goals of the foundation.  The ones that don't appear on the site any more.  I truly believe the Pi could change the nature of computing in a way that no other computer has ever done, that it could make an understanding of computer science part of basic education.  Indeed, even if the foundation had never managed to get a single board out of the door, it has highlighted fundamental issues in education today, raised questions, and shown that, with a bit of will, something can be done.

But all that is being lost, being driven into obscurity by a botched sale of millions of cheap, credit card sized computers running XBMC.

Badly.

I hope the foundation people at least get to pay off their personal loans, but I assume Farnell and RS are taking a substantial cut of the already slim margins.

[1] Arguably, the handing over of sales to people like RS and Farnell should have happened around December, when the beta boards landed.  At that point, the hype was containable. But that's with hindsight, and I guess at that point the foundation guys and girls still wanted to (and believe they could) keep control, which is understandable.