Well correct me if I'm wrong but this seems to come down to how many
flops it can do, the moving of variables and such is probably a minority
of the processing. That's why I wanna focus on the flops requirement.
How much resources does RTKLib consume on Beaglebone? Because BB being
faster and capable of RTKLib still doesn't establish the processing
requirements. Is it running at 60% core utilization or 5%?
I did run RTKLib on my i7 Q 740 1.73GHz laptop and the utilization was
basically nil. I really couldn't determine anything from that, the
usage figure was too low to give a meaningful number, not when the
capabilities are at least 100x greater. I mean if the usage was 10% on
that i7 I could pretty well dismiss it working on a Cortex M4. IIRC it
was like a single-digit or fractional % though and the OS can consume
considerable resources managing the busses and displaying the maps and
interfaces so that doesn't mean much.
Raspberry PI would be nice, but I can't get ahold of one, much less will
it be readily available at this time for widespread consumption if the
application worked. I'm still uncertain if widespread, long-term,
low-price distribution is gonna happen or just turn out to be
vaporware. STM32F4, anybody CAN order one or a thousand and get them
for $15 or better right now. Still got high hopes of course. Raspberry
PI also wasn't designed with a lot of low-level hardware interfacing so
it'd still require a daughterboard like the STM32F4 to interface with a
rover's motors and sensors and all.
Danny
On 5/2/2012 3:40 PM, Michele Bavaro wrote:
Hi Danny,
I strongly doubt that a STM32F4 will be able to run RTKLIB.
It's true that it runs on a beaglebone, but Cortex-A8 has around
2MIPS/MHz and runs at frequencies close to 1GHz,
whereas a Cortex-M4 has 1.25MIPS/MHz and runs at frequencies up to
150MHz: there is almost one order of magnitude.
In addition since the structure of rtkrcv is quite strongly coupled
with a Linux OS,
there will be a lot of effort required to port it to a lighter RTOS,
let go to bare metal code.
But I don't want to discourage you.. if you think it's doable go for
it :)
Best regards,
Michele
On 02/05/2012 00:15, Danny Miller wrote:
STM32F4 "demo board" uses an Arm Cortex m4. 32 bit, 210 DMIPs and a
single-precision hardware FPU. I'm slightly unclear on the memory
space it has on this specific board but it should be 192KB SRAM and
1MB flash. That's my porting plan.
If it WORKS, it'll be a great system, these boards are absurdly
cheap. It is several more orders of magnitude of capability than
these 8bit PICs and such, but I don't understand the scale of the
flops requirement of RTKLib. I know it's somewhere between "much
more than any 8-bit controller could ever do" and "won't even make
Intel i7 break into a sweat". And those are wildly different
magnitudes. I don't know exactly where RTKLib 10Hz would be between
those.
And it's be running RTKLib and just some minor application
(navigation and monitoring) code which will not be
processor-intensive, and it's not using Linux or an RTOS. So there's
not a significant overheat for other tasks and the overhead's timing
can be managed predictably and accurately. Pretty much the core can
either do it or it can't.
Danny
On 5/1/2012 4:43 PM, julio menezes wrote:
Hi Danny,
I have a core with a hardware FPU, but it's only capable of
doing Single floats, not Double. It is going to break
things to implement the specified Double calcs with Single
precision? I would assume so, but it's worth asking.
The RTKLIB author T.Takasu and A.Yasuda have ported RTKLIB to a
BeagleBoard which has an ARM Cortex-A8- with 1 GHz and floating
point, I do not know if double or single precision.
I plan to move in this direction also, may be using a hardware less
powerful but cheaper.
Raspberry Pi
http://www.raspberrypi.org/faqs
The SoC is a Broadcom BCM2835.
This contains an ARM1176JZFS, with floating point, running at
700Mhz, and a Videocore 4 GPU.
I am waiting, anxiously, the RTKLIB 2.4.2 version with RTCM-104
phase messages encoder to built a local base station as where I live
there are no near NTRIP network ( less than 10km ).
good luck,
julio menezes
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