I2C and GPS

Lars Poulsen larsopoulsen at gmail.com
Thu Nov 24 14:49:44 CET 2011


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> 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
> 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 wrote:
>
>> On Tue, 22 Nov 2011 21:20:16 -0500
>> Benjamin Deering<ben_deering at swissmail.**org <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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