[TangerineSDR] I2C Extension - 30 m verdict- too flaky for now.

[Tom McDermott]

Hi Dave:

The I2C interface needs to run at the 100k rate for 100 feet,   400k is too
fast.
First thing I might check is the value of the +5 VDC voltage present at the
remote end.
It needs to be great enough that the +3.3V regulator is capable of working.

-- Tom, N5EG


On Fri, Feb 28, 2020 at 11:18 AM David Witten via TangerineSDR <
tangerinesdr at lists.tapr.org> wrote:

> It looks like the verdict is in on using full magnetometer support boards
> with a single span of CAT 6a shielded twisted pair cable - for now.  The 30
> m (100foot) cable does not seem to work satisfactorily.
>
> It seems clear to me that it works 'a little', I2cdetect reports devices
> at 0x18  (MCP9808), 0x19 (MCP9808), and 0x20 (the RM3100 module) most of
> the time. Since I am doing this testing from the NVIDIA Xavier the bus used
> is /dev/i2c-8.  I have no idea what that is at 0x74.
>
> From code written in C the device setup and verifies  the revision id of
> the RM3100 most of the time.  But then errors seem to accumulate and
> timeouts occur.
>
> I'm not even certain at the moment which I2C signalling rate is in use
> here.  It is just the default, perhaps 100 k.  I'll look into mechanisms
> for lowering the rate used. I think that I saw an ioctl() call that may
> help.
>
> So for now 50' seems rock solid, 100' is too flaky to use.  I'll try to
> find a way to connect a 50' with a 25 cable to see where that gets us.
>
> The cable used is Amazon's pride off-the-shelf overnight stuff.  The
> package says (in very small type):
>
> 100' Cat 5a
> 550 MHz
> Snagless Shielded (SSTP/SFTP)
> Gigabit Ethernet Patch Cable - Black.
>
> I do not know the wire gauge used.
>
> Results on Xavier (same on Odroid-N2):
>
> dave at rio:~/projects/SWx/Software/SWx-C/i2c-c$ sudo i2cdetect -y -r 8
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:          -- -- -- -- -- -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- 18 19 -- -- -- -- -- --
> 20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- 74 -- -- --
> dave at rio:~/projects/SWx/Software/SWx-C/i2c-c$ sudo ./simplei2c
> i2c_init OK!
> RM3100 Detected Properly: REVID: 22.
> Polling I2C device: 20.
>
> readRegister set register: Remote I/O error
> readRegister set register: Remote I/O error
> readRegister read value: Resource temporarily unavailable
> readRegister set register: Connection timed out
> readRegister read value: Connection timed out
> readRegister set register: Connection timed out
> readRegister read value: Connection timed out
> readRegister set register: Resource temporarily unavailable
> readRegister read value: Remote I/O error
> readRegister set register: Remote I/O error
> readRegister read value: Resource temporarily unavailable
> readRegister set register: Remote I/O error
> readRegister read value: Remote I/O error
> readRegister set register: Remote I/O error
> readRegister read value: Input/output error
> readRegister set register: Resource temporarily unavailable
> readRegister read value: Remote I/O error
> readRegister set register: Remote I/O error
> readRegister read value: Remote I/O error
> readRegister set register: Input/output error
> readRegister read value: Remote I/O error
> readRegister set register: Input/output error
> readRegister read value: Remote I/O error
> readRegister set register: Remote I/O error
> readRegister read value: Input/output error
> readRegister set register: Connection timed out
> readRegister read value: Connection timed out
> ...
> etc.
>
> Dave Witten, KD0EAG
>
>
> --
> TangerineSDR mailing list
> TangerineSDR at lists.tapr.org
> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>
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