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Re: [gpsd-dev] ARM port problem in rtcm3.2 handling
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From: |
Gary E. Miller |
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Subject: |
Re: [gpsd-dev] ARM port problem in rtcm3.2 handling |
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Date: |
Wed, 20 Apr 2016 12:25:52 -0700 |
Yo Hal!
On Wed, 20 Apr 2016 04:10:13 -0700
Hal Murray <address@hidden> wrote:
> I thought that Raspberry Pi was normal endianness.
'normal'? Which is 'normal', big-, little-, or bi-endian?
x86 has always been little-endian. ARM originally was big-endian, then
evolved at V3 to bi-endian.
Since ARM is now bi-endian there are both big- and little-endian Debian
ports.
Luckily the most common abi for ARM is currently armhf, which goes
little-endian, just like x86. But unlike x86 someone could also be
running a big-endian port on ARM. You need to know which ABI is on
use on ARM to know endian-ness.
And to make it worse, ARM can use middle-endian 32bit words!
https://en.wikipedia.org/wiki/Endianness
I think gpsd is pretty good about endianness, but I suspect there
are some problems lurking deep in the RTCM decoder.
When I did microcode, in the Cretaceous, I found that big-endian
produces much smaller microcode.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
address@hidden Tel:+1 541 382 8588
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