Michael Zucchi

 B.E. (Comp. Sys. Eng.)

  also known as zed
  & handle of notzed


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Friday, 05 March 2010, 12:43

Strange week.

Phew, another week down. That was a pretty long one. New job, all sort of things to learn about.

I went with CentOS for my workstation ... hmm, but i'm not really all that pleased so far. It's mostly working but there's a few weird bits. xterm's keep dying occasionally while i'm using them - they lock up hard and I can't even close the window. I have 'focus follows mouse' on, but it isn't always working properly - if the machine is busy when I move the mouse it seems to do weird shit. I also had a locked pointer grab - gee, I haven't had those outside of using gdb for years and years. And today I was switching virtual desktops and it just went mental - keep cycling the windows as fast it could once I let go of the keyboard (it still accepted keystrokes as the windows whizzed by) - had to kill X. The whole machine feels pretty slow too - it is an older machine being re-used, but it feels slower than it should. Might be the encrypted home mount too ... and ext3 must share some blame too. And finally the lack of packages - I expected it to be more limited than other more bleeding edge systems i've used lately, but the lack of packages is really stark; some what I thought really basic 3rd party packages are simply missing. I guess i'll have to re-install it with something a bit more production ready; CentOS 5.4 just isn't, at least for my needs. Sigh, not really what I wanted to have to do - stability is pretty much the whole reason I was looking at CentOS anyway.

As part of work i've been reading about convolutions and fft's and other fun stuff. Not all new to me, but I've never had to use it in anger before so it's pretty interesting delving into it. Unfortunately my maths was never really up to scratch in this area ... on the other hand I just have to use it, not derive it. Octave works pretty well for playing with ideas, and gnuplot does some nice plots too. Maybe if I come up with some interesting stuff as i'm learning I'll post some shots, but i'm a bit too worn out this week.

Last Saturday and today I spent a couple of hours shifting road-base and filling up the trench and tamping it down. Pretty hard work but not that bad in short spurts, and the trench is just about where I need it - 12 barrow loads so far. I was going to get some sand for the final layer, but I might try with the roadbase since I have it, and would have to move it all before I can order any sand. It's a lot harder making it level though, so I may regret that idea. I'll see - should really do some more on it this weekend, but there's other things I should probably do too. It might rain anyway (hmm, rain, i've forgotten what that feels like).

Tagged biographical.
Monday, 01 March 2010, 06:03

Context switching

After working on it in bits and pieces over the last few days I managed to get context switching working (late) last night.

Again apart from one little error it might've happened a lot sooner - I read the APSR description about the 'big endian bit' and I think my mind just assumed 'not x86 ==> big endian' and I decided I needed to turn it on. Oops. Very odd, apparently scheduling tasks just fine but they don't seem to execute at all, nor cause any crashes. Oh this is the first time i've had user-mode code executing as well.

My initial idea was to only save the minimal state possible on interrupt entry, and only bother with a full save/restore in the event of an actual context switch. But then thinking about the microkernel design I want to implement later on, this seems a bit pointless since generally the `low' part of the interrupt handler will always run straight away so it will probably lead to a context switch. This simplifies the context switcher a little bit and adds a bit more flexibility internally too. For system calls i'm not so sure yet - quite a few system calls should lead to a context switch too but a lot wont, so i'm still thinking about whether it will work the same way. And I have to decide if system-calls can be interrupted - if they remain very tiny then they wont need to be.

The context switch code basically ends up the same as the one out of the manual, but hooked into the normal IRQ handler. The IRQ stack pointer is used as the point to ThisTask.tcb.regs[0] all the time, so nothing needs to be loaded at interrupt handler time. I have a trivial ASM function which lets the system code set the next task to run:

        @ r0 = pointer to r0 in tcb
        .global irq_new_task
        mrs     r1,cpsr
        cps     #MODE_IRQ
        mov     sp,r0
        msr     cpsr,r1
        bx      lr

The function below then becomes the new IRQ entry point. The lines highlighted in bold indicate the changes from the previous interrupt handler - there aren't too many, and one is just a cleanup (the mov lr,pc). The main difference is that all of the context state is stored on the `irq stack' rather than the supervisor stack. But it isn't really a stack, it's just a pointer to the TCB. This does have one consequence - it is impossible to implement re-entrant interrupts (at least without further code). If more state is required it may make sense to shift all interrupts to use fast interrupts, since it could then use the other FIQ banked registers to store per-processor state - although it could equally just be a pointer from the TCB to a per-processor or per-process struct.

        .global irq_entry
        sub     lr,#4
        stm     sp,{ r0-r14 }^          @ save all user regs
        srsdb   #MODE_IRQ               @ save spsr and return pc

        cps     #MODE_SUPERVISOR
        push    { r12, lr }             @ save supervisor lr and r12 to supervisor stack

        ldr     r5,=INTCPS_BASE         @ find active interrupt from INTCPS
        ldr     r0,[r5,#0x40]
        ldr     r2,=irq_vectors         @ execute vectored handler
        and     r0,r0,#0x7f
        mov     lr,pc
        ldr     pc, [r2, r0, lsl #2]

        mov     r1,#1                   @ tell INTCPS we've handled int
        str     r1,[r5,#INTCPS_CONTROL]

        pop     { r12, lr }             @ last of state on supervisor stack

        cps     #MODE_IRQ

        ldm     sp,{r0-r14}^
        rfedb   sp                      @ back to new or old task

Now the IRQ sp is just used as a pointer to the current TCB - so the code doesn't perform any write-back to the sp when writing or restoring values. The user registers are stored/restored above it, and the pc and spsr registers are stored below it. The push { r12, lr } doesn't actually need to store r12 since we already saved it, but this is used to keep the stack aligned at this point - it will need to change to ensure the alignment specifically so r12 wont need to be saved once that is done.

struct tcb {
        uint32_t pc;
        uint32_t spsr;
        // <- sp_irq points here always
        uint32_t regs[15];

The C structure that maps to this is shown above, indicating where the sp_irq actually points. I have a simple linked-list of tasks to hold this state, and whatever other state the kernel might need.

struct task {
        struct Node Node;
        int id;

        struct tcb tcb;

Within an interrupt routine, if I wish to schedule a new task all I need to do is call the aforementioned irq_new_task function with the value from inside the tcb, and that task will run once the interrupt is finished.

Although not particularly practical in the real world, a round-robin scheduler of all tasks in the run-queue is as simple as:

        AddTail(&tasks, &thistask->Node);

        thistask = (struct task *)tasks.Head;

There are (at least?) two other pieces of context that also need changing in a complete system, the MMU tables and the floating point registers.

Floating point registers don't need saving/restoring here because the kernel will never use floating point itself. And instead of wasting the time saving/restoring full FPU state at every interrupt, the code will just find out when a floating point instruction is used and swap the state then. The irq_new_task call can probably just disable the floating point unit, and when an undefined instruction interrupt occurs on the floating point co-processor the state can be changed then if it needs to be. And/or some combination there-of. e.g. irq_new_task could check which task `owns' the FPU and enable/disable it appropriately.The MMU is a little trickier, it will need the page tables changed at every context switch. Since I will map the system memory globally across all tasks, I will probably also be able to put all of that logic into irq_new_task as well. Not sure how i'll deal with system calls that cause a context switch yet. I am looking at a process+task model too, so each task will be associated with a parent process which will encompass the memory map, so for example, a mutli-tasked process wont need an MMU switch if it is only switching between tasks.

And finally the last piece of the puzzle is boot-strapping the task system. There is only 1 CPU and it can only execute one bit of code at a time, so basically the initial booting process just 'falls through' to the 'current task' and automagically just starts executing as part of it's context. There is actually very little that needs to be set up - simply changing to user mode, and then initialising it's stack pointer, and that's it. The code then jumps to what is the entry point of the current task (as defined by the context switching mechanism above).

        // <- in supervisor state here, with boot-strap stack, etc
        asm volatile("cps #0x10");
        // <- user mode, undefined stack pointer
        asm volatile("ldr sp,=0x88000000 - 32768");
        // <- now sp is set to tasks's stack

The code above is just a demo, but the final thing will just jump to the idle task, so it can still be hard-coded in a similar way. Or it can be even simpler - the idle task does not need any stack, e.g. the following would suffice.

        b idle_task

Code not committed yet.

Hmm, not sure what to look at next, maybe MMU context switching, or perhaps something simpler like system calls. Really exhausted tonight - spent the whole day staring at code not written by a programmer, and I need a good meal too.

Maiden Century

This is my first web diary that's made it to 100 posts, that being this post. Yay.

Tagged beagle, hacking, puppybits.
Saturday, 27 February 2010, 08:36

Sick and tired of being a permanent beta-tester.

Sigh. I was really angry about this, but now I'm just disappointed.I'm just sick and tired of being a permanent beta-tester, or even alpha-tester, for `linux distributions' and much of the software they use. That was never terribly cool, but it was entirely acceptable up until about the turn of the century. But today there's no excuse anymore, and really only one way to describe it, and that's bullshit. It just doesn't seem to be getting better either, and if anything seems to be taking a turn for the worse in the last few years (Notwork Manager, Puss Audio, KDE 4, EXT4, anything from f.d.o, and so on).In the usual bullshit goal to add new features, stability and usability are being cast aside in the permanent quest for shiny. It certainly isn't confined to the linux world - just look at vista or apple - but they don't affect me personally so i couldn't care less.

The latest case to affect me being Grub 2 (apparently it's been in use for a while, but today is my first experience with it). I installed Ubuntu 9.10 on a fresh system, and it just doesn't boot. No problem ... go to rescue mode and fix it. Ahhh, what the feck is this mess? They've turned the boot-loader into a friggan `platform'. I don't want to have to learn a whole new over-engineered `script' format, together with each distribution's overly extensible frame-work designed to make it `usable' - for something that doesn't work anyway, and wont add anything most people need. It's just a bloody boot loader after-all. I know grub had some issues, but it just doesn't need a huge run-time extensible module system and sophisticated scripting platform to copy a disk image to ram and change the cpu's program counter to point to it. And particularly since they still seem to be short on developers - the last thing they need is to make it more complex.

It's a fundamental problem which starts at the project developers and filters it's way through to the distribution makers - but ultimately it is the distribution makers who are making the wrong choice. For starters, if basic things like sound, network, or booting don't work, they rightly bear the brunt of the anger. They are responsible for not just compiling a group of disparate projects and ensuring they work together, but that the application choices actually work. Distributions too often seem to confuse `stable' with `unmaintained' as well - the noisiest busiest projects get the attention, even if an alternative already does the same thing but isn't being actively developed any more since it doesn't need to be. And their choices can have pretty negative effects on projects; including a project 6 months before it is actually ready for production use can leave a sour taste in many users and tar it's image for years.

Project developers do need to take their share of the blame too. Sure nobody wants to maintain old software forever, but if they decide to drop support for and old product, they had better make sure the replacement works pretty well before pushing it for inclusion into distributions (or accept that nobody will use it till it does). Too often unwanted software is forced onto all users as a way to ensure it gets the testing required to make it a complete product, or worse, to ensure a competing project doesn't gain a footing (this is particularly problematic inside Linux where politics has started to blatantly undermine merit). As much as I dislike it, I realise this is part of Fedora's policy, so it can be excused to some extent, but most distributions actually promise a usable system from the start.

I guess i'll try Centos again - I tried it earlier but I couldn't get dual-screen working, and the network went all strange when I went to download decent drivers (the former not entirely their fault - bloody nvidia) ... hmm, maybe I shouldn't bother. And if that doesn't work easily I guess it'll have to be Fedora 10, or perhaps an earlier Ubuntu. At least they just worked as far as I need them (i.e. I don't need sound).

I suppose this strategy of avoiding the unstable shiny shit will work for a couple of years ... and hopefully by then the distributions will have got their fracken shit together, but somehow I just don't think that will happen.So you might be wondering - just what are you doing about it then, you whiney prick?

Well for starters, there just isn't anything I can do about Linux or it's distributions - they are too big with their own culture and momentum - and way too much politics. At the most I might be able to write a small application or work on a larger one with other people - but that wouldn't have any impact. Even when I was working on Evolution I didn't have full control of the project, which sometimes stopped me fixing some of the larger problems. And too often I find myself in the minority and don't have the skills to make my case effectively (for example it is pretty hard explaining something when you think it's so obvious it shouldn't need any).

I have poked around AROS a little bit, and Haiku - I dislike a lot of the way GNU/Linux works and I think the only practical solution to that is just a completely different OS. But so far I just haven't been able to get into them for whatever reason, and sometimes you just have to work to your own strengths - and perhaps working on such projects just isn't for me. I think Haiku probably has the most promise at this point, and I think AROS is a little too conservative in it's goals to ever be really useful for most people. I think that despite always screaming for them, projects like these secretly don't really want any new developers anyway - the developers are quite happy to make their little wins on a system completely of their own devising, without having to worry about the politics and simply the hassles of dealing with anyone new. And I think that's an entirely reasonable approach to take too if you're in it for the hobby - it's a hell of a lot more fun that way for starters, and why else would you be doing it?

PS The pile of dirt hasn't moved, but I did have a pretty good nap - although that'll probably just mean a late night!

Tagged rants.
Saturday, 27 February 2010, 02:03


Ahah, well starting work again Monday. Sounds like it could be more interesting than I thought. But I guess time will tell. It might be keeping me pretty busy for the first few months too, but hopefully I still have time for the distractions offered by the beagleboard.

Rode to a meeting and rather than taking the train, which was probably a bit unwise. Apart from not preparing properly and meeting in a cycling jersey ... the weather was unexpectedly hot yesterday (the forecast the day before was about the same but it was no-where near as hot on the road). Every time I put a bit of oomph into it I started to feel a bit weird from over-heating, so had to take it pretty easy most of the way (only about 24km each way). Apart from not having ridden much lately and so not having a decent summer acclimatisation, I think it mostly just comes down to badly needing a haircut and getting a super-hot head from the bouffy hair. Well, having a dreadful hangover and 5 hours of sleep didn't help i'm sure.

The day before I got out and had a look for old computer stuff in pawnbroker shops. Didn't find much, although there were a couple of shops tucked away which had a fun range of old tools and other junk which might merit another visit one day. I did pick up an old keyboard that looked hardly used. I took all the keycaps off and gave them a good wash, and it looks almost new now (apart from putting the - and = on the wrong way around). Oh apart from that **it's just a keyboard** - none of those bullshit `multimedia' keys or even worse - windows keys! It's even got a steel base. It's the little things sometimes ...

On the way home yesterday I ordered some roadbase so I can get stuck into the retaining wall at last (last day of holidays - the one i partly took to do such things - typical).

The dirt.

It got delivered at 8am - and I was all keen to go get a haircut so I can move it without passing out, but somehow the day is slipping away and i'm stuck doing little things around the house again. Almost feels like I still have the hangover from yesterday morning - but I didn't go out last night at all. I think I just need a really good sleep (and maybe some better meals), but seem stuck going to bed too late and rising too early.

The hole.

The trench isn't quite right, and I probably need to dig out the stairs before starting to fill it, but it's almost ready. I should be out there now, but it's a bit warm to be working in the full sun in the middle of the day (when you have a choice anyway). Have to drag myself out a little later to get stuck into it.

Tagged biographical, house.
Wednesday, 24 February 2010, 11:27

Smooth as a baby's bum

Well I didn't end up getting out, but I had a break for a while. I also started thinking about what I want to do now I have interrupts working and decided I couldn't be bothered doing too much with the vblank demo. But since there was nothing on TV for a bit I tidied it up and committed it as is.

It's moving smoothly, honest.

Yes, not much of a screenshot, but I thought the page needed some colour and a break from all the text of late. It just smoothly scrolls from one screen to the other and back again, drawing one box on the lower screen every time it's fully hidden. Demo in irq-scroll.c, with the interrupt code from yesterday in exceptions.S.

So what to do next. Well there's still the idea of a little game or demo or so, but i'm lacking a bit of inspiration, and besides, a bit of support to actually run the code in, for things like sound. So i'm starting to think about working on a little real-time micro-kernel.

Many months ago I had been writing one for x86 but got a bit pissed off with all the PC crappyness, and found something more interesting to do instead. So i'll probably start with that, although i'm not sure how much i'll end up using (not that I can remember the state I left it in anyway). For example, currently it does all the VM and process management inside the kernel (it made it simpler at the time), but I want to move that to a process instead so the kernel can work without any pre-emption or locks. Basically the goal is to make the kernel as simple as possible (nano-kernel?) without the simplification getting in the way. What I had been working towards was something like a mix of Minix 3 and AmigaOS; taking features like memory protection and processes from Minix, in addition to the asynchronous non-copying message passing, shared libraries, tasks, and the device mechanism from AmigaOS, with a bit of a reworking to make it all fit. Ahh well, maybe a tad on the optimistic side so I wouldn't hold my breath, on the other hand apart from device drivers there's not all that much to the core of such a design.

Not sure if i'll put it in PuppyBits or another project, but for now I still need to work out some basic routines like context switching and so on so i'll definitely put that stuff in PuppyBits at the least.

Tagged beagle, hacking, puppybits.
Wednesday, 24 February 2010, 00:25

Interrupt progress

Had another poke at interrupts late last night. And finally got a simple interrupt handler working. As usual a couple of simple mistakes initially thwarted my efforts.

  1. To start with I was trying to use the FRAMEDONE interrupt from the display controller. But it seems I needed to use VSYNC for HDMI out, and the EVSYNC_ODD/_EVEN for S-Video.
  2. I was using the rfe instruction, but neglected the ! on the register, so it wasn't fixing the stack pointer properly on exit. Somehow the application code managed to run ok for a few seconds with a constantly changing stack!
  3. I forgot to fix lr before saving it on the stack using the srs instruction (subtract 4). Again, rfe was thus skipping an a application instruction every interrupt, and again somehow the code didn't crash immediately either.

Other than using the ARMv6 instructions above, the code is basically straight out of the OMAP TRM § 10.5.3 MPU INTC Preemptive Processing Sequence, the step numbers below relate to that section. I haven't implemented the priority stuff yet (I was hoping it wasn't necessary for such a simple bit of code since I don't need priorities, but it seems it is for other reasons), so it doesn't actually implement re-entrant interrupts, but I might try to get that working before committing it.

        .set    MODE_SUPERVISOR, 0x13

        // 1. save critical registers
        sub     lr,lr,#4
        srsdb   #MODE_SUPERVISOR!
        cps     #MODE_SUPERVISOR
        push    { r0-r3, r12, lr }

        ldr     r3,=INTCPS_BASE

        // 2,3 save and set priority threshold (not done)

        // 4. find interrupt source
        ldr     r0,[r3,#0x40]

        // 5. allow new interrupts
        mov     r1,#1
        str     r1,[r3,#INTCPS_CONTROL]

        // 6. data sync barrier for reg writes before enable irq
        dsb                              // not sure what options it should use
        // 7. enable irq

        // 8. jump to handler
        ldr     r2,=irq_vectors
        and     r0,r0,#0x7f
        ldr     lr,=ex_irq_done
        ldr     pc, [r2, r0, lsl #2]
        // 1. disable irq

        // 2. restore threshold level (not done)

        // 3. restore critical registers
        pop     { r0-r3, r12, lr }
        rfeia   sp!

        .balign 4
        .global irq_vectors
        .word   exception_irq, exception_irq, ...
        .word   ... total of 96 vectors

The srs instruction and cps instructions are used to run everything on the supervisor stack/in supervisor mode. On entry the code is executing in irq mode, so it first saves lr_irq and spsr_irq onto the supervisor stack (after fixing the return address in lr!), and then switches to supervisor mode. Without the srs instruction (pre ARMv6) things are pretty messy since you either have to muck about with the irq stack first (and last), or have to switch between modes a few times to get everything sorted (see the links at the end of this post).I also implement a simple vectored interrupt table to simplify the C side of things, although I think I can just use a simple mov lr,pc before jumping to the vector rather than a literal load.

The ARM ARM actually recommends using the system mode for re-entrant interrupts (you can't use the interrupt mode itself because lr could be clobbered), so why am I using the supervisor stack? Partially historically because at first I couldn't work out how to save the state without clobbering some system stack registers (they're shared with user state). But I also have other plans where this scheme might work better, and if nothing else it stops broken code in user-mode crashing interrupts by breaking the stack pointer.

And finally one more thing I noticed whilst reading bits and pieces is that the AAPCS (EABI) specifies that the stack pointer should remain double-word (8-byte) aligned for entry points. I probably read it before but didn't take notice. This just normally means you always need to push an even number of registers onto the stack before calling other functions. Fortunately this just falls out with this code ... but with interrupt handlers which can be invoked at any time, we don't know what the alignment of the stack is so a specific check is needed too, according to the ARM Info Centre (damn, and I definitely know i've read that before just looking it up now - and it has some other important other bits too!).

Hmm, now i'm thinking about it ... i'm not sure I even need re-entrant interrupts at all. I'm thinking of working towards something along the lines of a microkernel architecture similar to AmigaOS or Minix 3, where device drivers are just high priority unprivileged tasks - the Cortex-A8 should be more than fast enough for this to work. All interrupt handlers will need to do is post events to these tasks, and the software will handle the priorities and whatnot. I suspect re-entrant interrupts are much more important in an embedded system where you just leave most of the work to the interrupt handlers, where DMA isn't available for everything, or the CPU speed is a limiting factor.

Specific Handler

The next step after the interrupt handler is the interrupt vector code itself. This is just a plain function call since the entry point has handled all the nitty gritty. But it still has to deal with the hardware - to identify which interrupt caused it to be invoked, and to clear it. Even with 96 interrupts in the interrupt controller, most of them map to multiple physical events.In the case of the video subsystem, there is a single interrupt DSS_IRQ (25) which can be triggered from 29 different events in either the DISPC module or the DSS module (actually I just noticed there are many more from the DSI module). § Interrupt Requests has a pretty good overview. Fortunately there is a couple of bits in the DSS_IRQSTATUS which lets the code determine which are asserted to simplify processing. After that test is made, each bit needs to be checked in turn and processed accordingly. And finally the interrupt bits must be reset by writing a 1 to each bit in the DISPC_IRQSTATUS or DSI_IRQSTATUS register - otherwise it will go into an infinite loop re-invoking the interrupt as soon as it exits.

void dispc_handler(int id) {
        uint32_t dssirq = reg32r(DSS_BASE, DSS_IRQSTATUS);

        // see if we have any dispc interrupts
        if (dssirq & DSS_DISPC_IRQ) {
                uint32_t irqstatus = reg32r(DISPC_BASE, DISPC_IRQSTATUS);

                if (irqstatus & DISPC_VSYNC) {
                        ... do vsync code ...

                // clear all interrupt status bits set
                reg32w(DISPC_BASE, DISPC_IRQSTATUS, irqstatus);

        // check for dsi ints (to clear them)
        if (dssirq & DSS_DSI_IRQ) {
                // not expecting this, just clear everything
                reg32w(DSI_BASE, DSI_IRQSTATUS, ~0);

This is basically the same process that all interrupt handlers need to go through. Identify the source, handle it, clear the assertion.

There are lots of 'gotchas' with interrupt handler writing at first, but the main thing is to not call any functions which share state with non-interrupt code. e.g. anything non-reentrant, or using hardware registers. Oh, and they should always run as fast as possible - all the `real work' your cpu could be doing is halted the entire time the interrupt is executing, and you could be processing thousands per second in a busy system.

The last piece of the puzzle is the interrupt enable masks. You don't just get all interrupts possible in the system all the time, you can mask (or enable) which ones you want to receive. This is all set-up before interrupts are enabled but after the hardware in question is setup. Here I clear all the status bits as well, just to make sure I don't get an unexpected surprise when I enable CPU interrupts later.

        // disable all but vsync
        reg32w(DISPC_BASE, DISPC_IRQSTATUS, ~0);
        // dss intterrupt can also receive DSI, so disable those too
        reg32w(DSI_BASE, DSI_IRQENABLE, 0);
        reg32w(DSI_BASE, DSI_IRQSTATUS, ~0);

I think I have some sort of set-up bug because I think that i'm sometimes getting interrupts when no event i'm testing is asserted. I will have to check the extra DSI interrupts I just noticed whilst writing this - they should all be masked off (should be reset condition anyway, but ...).

My little demo code right now just does a vsync'd smooth-scroll by changing the video dma base registers. The TRM states that the register is a `Shadow register, updated on VFP start period or EVSYNC.' There is another little trick though, it looks like all DISPC registers themselves are shadowed again, so you always have to set the GOLCD bit in DISPC_CONTROL whenever you make changes for them to make their way to the hardware. I guess I realised that anyway, but initially forgot.

        // update the graphic layer 0 address (video out) to scroll it
        reg32w(DISPC_BASE, DISPC_GFX_BA0, addr);
        reg32w(DISPC_BASE, DISPC_GFX_BA1, addr);

I might come up with a more impressive demo before committing though. Actually now I have interrupts working it opens up a lot of possibilities, such as a real sound driver, serial driver, and proper timing events (in a very odd twist, sometimes my delay loops seem to run twice as fast as other times ...).


I came across a couple of links on the internet about bare-metal ARM coding, some of it doesn't apply/wont work on OMAP3, but the general ideas are the same.

Oh, I finally got out in the yard yesterday - if only for a couple of hours. More or less finished the trench for the main retaining wall foundation. Now I just need to get off my lazy bum and order some road-base and sand. Can't say I felt the fittest - easily out of breath, although I'm sure that has something to do with the sleep apnoea, my particularly poor sleep the night before (i let the cat stay in and he was wandering around all night), as well as my bum sitting. Glorious day today, and no meeting organised yet about work, so I should probably get out on a bike. Maybe I can scan a few pawn shops in the extremely unlikely event any have C64's lying around.

Tagged beagle, hacking, puppybits.
Monday, 22 February 2010, 08:04

The cult of stupid

I've been thinking about writing about this for some time, and even written a couple of posts, but I was never happy with how they ended up.

Is it just me, or does it seem as though a new religion has started to gain hold, at least amongst the west. And the religion I speak of is a religion of stupidity and ignorance. All religion relies on a certain level of ignorance in order to maintain the integrity of their flock, but this new one is taking the idea to a whole new non-denominational level.

One only has to see any discussions that arise when climate change is mentioned, or recently almost any science-related topic.

The discussion quickly devolves into a slanging match against science in general. All sorts of people pop out of the wood-work in an incessant and boorish tirade of willful ignorance and stupidity. That people can mis-understand science to such a level in an age of universal education and information access is simply astounding. Unless every argument is framed in the purely black and white, good vs evil terms of an undeveloped mind, they cannot grasp it (or at least, this is the impression they wish to give). Science of course does not work this way, even scientific `facts' are not solid. Science only works because of informed scepticism (e.g. don't believe what you're told, without reason), but these fools are not sceptics. They are deniers.

So I wonder, just from where is this stupidity springing forth? Or more importantly, how is it able to gain a hold in such educated societies as Australia and the UK?

I have some ideas, but for now, the following is the article which finally prompted me to publish my thoughts. It is very sickening reading. It is the first part of a five part series discussing this new religion against science, and has already attracted over 500 comments at this time. Whilst the abusive e-mails in the article are alarming, the numerous comments are simply depressing - it seems that Australians really are that stupid.

I await the follow-on parts with interest.

Bullying, lies and the rise of right-wing climate denial.

Tagged politics.
Monday, 22 February 2010, 03:08

Well so much for that.

Well that was an odd week. I did a lot of nothing ... instead of getting out and about or digging in the garden I spent most of it reading about the world's woes and getting worked up about it.

Maybe I should've stuck with the coding, but my mind did need a little rest anyway.

I'm pretty much resigned to the fact that I will have to get USB working ... but boy is it a lot of work. The *BSD and Linux implementations are massive - although I don't need anywhere near that sophistication. The Haiku one is about the only other public free implementation I've been able to find (and in-fact the only with a suitable license), and thankfully it is much simpler, although in C++. Most other free operating systems just don't implement USB. Maybe I should just shelve that whole idea and try and get Haiku working instead ... but my last patch hasn't gone anywhere so I lost some interest in that.

I did have a little play with trying to get interrupts working ... but no real progress on that front yet.

Another side-track was that I ended up with an old casio electronic keyboard to play with (for nothing). Given I have so much spare time I thought i'd try and learn a little piano, or at least see if I can drum up enough interest to want to learn it properly. Still not sure yet, my fingers seem to seize up pretty quickly, but it passes the time in the sort of cathartic way that reading the news or programming doesn't.

It gave me other ideas too, like hooking it up to a beagleboard, since I have a spare one still sitting in it's box. There are enough GPIO pins to hook up the matrix scan directly, although the 1.8v level logic adds a twist. Could make a fun little synth, even if I can't play it properly. Alternative is to use a smaller part like a PIC or AVR to decode the keyboard and ship out USB, serial, or even midi. Haven't played with hardware for ages.Somehow that got me onto another site (through hack-a-day) that had some guys remarkable efforts with old Commodore 64's. I could just use the keyboard and box to put a beagleboard in to make a usable computer and not have to worry so much about USB and the like (and even if I just ran some version of linux on it, it would make a nice box to put everything in, particularly the C64-C or Amiga 600 cases).

My brother still has a few old computers at home, so I might try and get one

(shit, he threw them all out!), or ask around.

Tagged biographical.
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