Re: lua on ARM7

[bert <bestanf@...>]

Hi Asko, all,

Sorry, I've been out of the office for a few days and not keeping up with this thread.

Anyway, I'm definately interested in that SDL_mixer example.. might help clear up some stuff. 

I was thinking of using LUA to process samples from the ARM's on-board analog-to-digital converter, but it looks like that would be asking too much. 

So my next question is.. how hard is it to compile LUA to ARM7 assembly :-) 
maybe Thumb mode ...

I realize it would be very complicated, since you would need the garbage collector. but what if I limit it to compiling a LUA function like this :

    function process(input1, input2)
        return input1 * input2
    end

I guess that wouldn't be too hard? I'm not sure if there exists a lua scanner/parser in LUA itself...

what if it gets more complicated: 

    lut = [0, 0, 0, 0, ... 0]   
     --- say, 256 values in lut 

    function process(input)
       return lut [ input ]
    end

or what about this :

    function process(input)
       local t = [math.random(), math.random(), math.random()]
       return input * t[math.random(3)]
    end

I know these functions don't make a lot of sense but I'm trying to get a general idea of how to go about this. 

I'd like to have some function in LUA that does something like this 

    funBinaryCode = compileARM(function (input1, input2) return input1*input2 end)

--- funBinaryCode now holds a table of bytes which can be cast to a function pointer on the ARM7 and called

Any comments highly appreciated.

Bert


Asko Kauppi <askok@dnainternet.net>
 wrote:
>  
> Ah, yeah.
>
> Your flag thing is a "one entry queue" but I was expecting Bert not  
> to want to lose a single interrupt (and them to be different, like  
> having some data values attached, that Lua would care about).
>
> Anyways, already this is getting speculative, since we don't know  
> what Bert does. Bert: if you want an event dispatch queue, I can send  
> code I've used in LuaX/SDL_mixer, to catch played music samples at  
> real time (and show the graphs by Lua). Don't remember about memory  
> allocation, but yes, most likely one alloc per interrupt is needed  
> there.
>
> -asko
>
>
> David Given kirjoitti 15.5.2006 kello 20.00:
>
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > Asko Kauppi wrote:
> > [...]
> >> I would consider doing an "event dispatch" interrupt handler (in 
>  
> >> C) that
> >> would sit in the other end of a FIFO queue, the other end being  
> >> polled
> >> by Lua (can you run one instance, as the main loop?) to take in
> >> "commands".
> > [...]
> >
> > A common technique is to have the interrupt handler set a bit to say
> > 'this interrupt has happened'. Your userspace code then polls all the
> > various bits, does its work, and then clears them again. Getting the
> > logic right to ensure that all interrupts are properly serviced is  
> > a bit
> > challenging, and of course you lose any kind of real-time-ness, but it
> > does allow you to avoid having to allocate memory during your  
> > interrupt
> > handler.
> >
> > - --
> > +- David Given --McQ-+ "Preacher, don't the Bible have some pretty
> > |  dg@cowlark.com    | specific things to say about killing?" "Quite
> > | (dg@tao-group.com) | specific. It is, however, somewhat
>  fuzzier  
> > on the
> > +- www.cowlark.com --+ subject of kneecaps." --- Firefly, _War  
> > Stories_
> > -----BEGIN PGP SIGNATURE-----
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> > Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
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> > =lHJf
> > -----END PGP SIGNATURE-----

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