I2C and GPS

[Alastair Johnson]

Given the performance degradation in GPS lock cause by high SD drive 
strength and the i2c being on flying leads right next to the antenna I 
certainly wouldn't rule it out.

On 11/24/2011 01:49 PM, Lars Poulsen wrote:
> Hi
> You can try to add a series resistor to the signals or reducing the
> drive strength of the driver.
> The frequency of the signals are not that important but rather the rise
> time.
> This is usually not a problem om i2c but  who knows.
>
> On 24/11/2011, at 14.17, Dave <dave.tv at gmail.com
> <mailto:dave.tv at gmail.com>> wrote:
>
>> Hi,
>>
>> Ferrite beads aid with removing VHF-SHF feedback and/or uncontrolled
>> oscillation mainly. I cannot see why they would be of use on a
>> (500khz?) I2C bus. At that frequency they would have minimal effect.
>>
>> On Thu, Nov 24, 2011 at 9:44 PM, Benjamin Deering
>> <ben_deering at swissmail.org <mailto:ben_deering at swissmail.org>> wrote:
>>
>>
>>     With the i2c devices removed, I get TTFF of around 1 minute in
>>     shr-core.  It sounds like putting ferrite beads on SDA and SCL
>>     might help reduce EMI, so I will try that when I get a chance.
>>
>>     Ben
>>
>>
>>     On 11/23/2011 05:06 PM, dmatthews.org <http://dmatthews.org> wrote:
>>
>>         On Tue, 22 Nov 2011 21:20:16 -0500 <tel:16%20-0500>
>>         Benjamin Deering<ben_deering at swissmail.__org
>>         <mailto:ben_deering at swissmail.org>>  wrote:
>>
>>         Hi Ben
>>
>>         Not sure this is relevent to you, but I now have the fastest
>>         GPS fix I've ever had on the freerunner.
>>
>>         QTMoko v35 and I put this in /etc/default/gpsd:-
>>
>>         START_DAEMON="true"
>>         GPSD_OPTIONS=""
>>         DEVICES="/dev/ttySAC1"
>>         USBAUTO="false"
>>         GPSD_SOCKET="/var/run/gpsd.__sock"
>>
>>         Before doing this it was pretty poor - worse than earlier
>>         versions of qtmoko and much worse than every SHR I've tried.
>>         On a reasonably clear day I now reliably get a fix in under a
>>         minute, sometimes within a few seconds.
>>
>>         The only other varying factor (doubtful relevence) is that I
>>         got pissed with QTMoko and to a lesser extent SHR foobarring
>>         the SD card, so I'm now running from the card instead of NAND
>>         and everything is pretty good
>>
>>
>>
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