Thanks Marc, I appreciate the candid input. I have a few final (I
promise) followups here that are more for my edification/learning than
anything else.
You say that RIOT is meant for *small* systems, and I think I'm
beginning to understand what that means. But regardless of what RIOT is
*typically* used for, are there any inherent limitations in RIOT that
would prevent me from deploying/flashing it to a sophisticated MCU that
*could* run Java? In other words, say I have an MCU that has a crazy
amount of ROM/RAM on it that has the stats to handle a full bore JVM
app...does RIOT itself have any limitation/constraints that would
prevent me from choosing it (nevermind *why* I would choose it in the
first place!)?
Also, I get that MCU ROM is the memory where the executable is flashed
to. And I understand that because of this, in order for a non-running
executable to "fit" on an MCU, it must have a file size that is smaller
than the amount of ROM (obviously). But I'm still not understanding why
the RAM (that is, the memory allocated to the running executable) can't
be scalable by somehow attaching additional storage (flash/whatever) to
the MCU. In other words, if the sam3x8e has 512KB ROM and only 96KB RAM,
if my entire JVM executable (which includes *everything*) is somehow
magically less than 512KB, it will fit on the MCU. So why can't I then
"get around" the 96KB RAM limitation by (somehow) integrating that
onboard 96KB RAM with, say, an 8GB solid state drive, or something
thereabouts. I just feel like there *must* be a way to scale the RAM
and perhaps even the ROM. Ideas?
Thanks again, if I can get answers to these I should be all set!
Best,
Zac
On 8/11/15 5:19 PM, Marc Sissom wrote:
Hi Zac,
Have you looked at the sam3x8e datasheet? Right on the front page it says it
has 512KB of flash (AKA ROM or nonvolatile program and data storage). The chip
has 96KB of RAM. Looking into task manager on Windows 7 I see a javaw.exe that
is occupying 133MB of RAM and my JRE takes up 153MB of disk. Admittedly this is
not a perfect comparison, but surely these numbers mean something to you.
RIOT is meant for *small* systems. Not SMALL or S M A L L but small systems. Some of these systems
are so small that they can't do "Hello World" because the "printf" code takes
up too much space.
Thoughts? Criticisms? Hate mail?
In other words, you're nuts!
;-)
Given that, here's a true Java bytecode chip that I worked with a few years
back:
http://www.ajile.com/index.php?option=com_content&view=article&id=2&Itemid=6
Here's an FPGA core:
http://www.jopdesign.com/
And an ARM product:
https://en.wikipedia.org/wiki/Jazelle
In other words, you are not the first to think of this, and in some cases it's
not a bad idea. On the other hand, I think you can safely forget Akka on RIOT.
You also mentioned Python; have a look here:
http://micropython.org/
Enjoy!
Marc Sissom
Krypton Solutions
-----Original Message-----
From: devel [mailto:[email protected]] On Behalf Of Zac Harvey
Sent: Tuesday, August 11, 2015 3:23 PM
To: RIOT OS kernel developers
Subject: Re: [riot-devel] HotSpot JVM on RIOT-OS?
Thanks Kaspar and Joakim,
I'm not trying to be difficult here (I promise!) I'm just trying to see the
forest through the trees.
When you say that "The OpenJDK would probably require many megabytes of both ROM and RAM, this
means it will not run on the sam3x8e...", why? Is it because it would require "many
megabytes", or because it requires ROM, which I'm guessing isn't supported by RIOT-OS?
And yes, I will definitely dive into Darjeeling/LLVM, but am trying to see if I
can't brute force an easier solution first. :-)
Thanks again!
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