can we have a picture of the final tweak please ?<br><br><br><div class="gmail_quote">2012/1/11 Benjamin Deering <span dir="ltr"><<a href="mailto:ben_deering@swissmail.org">ben_deering@swissmail.org</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Dusting off a very old thread...<br>
<br>
I have both of my sensors working and good gps performance now.<br>
<br>
This weekend I opened the position settings->satellite details dialog in SHR as well as my phone and tried a few things. I was seeing serious signal loss as soon as I connected the SCL line from the sensor to the test pad near the debug connector. I tried wrapping the SCL wire around a ferrite bead, and putting a decoupling cap between power and ground near the sensor. What ended up working was adding a series resistor on the SCL line. I grabbed a largeish SMD resistor from some volkswagen parts I had laying around (<a href="http://www.jeepingben.net/plog-content/thumbs/2010/volkswagen/large/995-dscf2246.jpg" target="_blank">http://www.jeepingben.net/<u></u>plog-content/thumbs/2010/<u></u>volkswagen/large/995-dscf2246.<u></u>jpg</a>). I thought I was grabbing a 470 ohm, but I guess it was 4.7k (marked 472). With this resistor in series everything works. I don't know if anyone else is adding i2c sensors to their freerunner, but I thought this might be helpful.<br>
<br>
Ben<br>
<br>
On 11/24/2011 11:36 AM, Alastair Johnson wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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.<br>
<br>
On 11/24/2011 01:49 PM, Lars Poulsen wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi<br>
You can try to add a series resistor to the signals or reducing the<br>
drive strength of the driver.<br>
The frequency of the signals are not that important but rather the rise<br>
time.<br>
This is usually not a problem om i2c but who knows.<br>
<br>
On 24/11/2011, at 14.17, Dave <<a href="mailto:dave.tv@gmail.com" target="_blank">dave.tv@gmail.com</a><br>
<mailto:<a href="mailto:dave.tv@gmail.com" target="_blank">dave.tv@gmail.com</a>>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<br>
Ferrite beads aid with removing VHF-SHF feedback and/or uncontrolled<br>
oscillation mainly. I cannot see why they would be of use on a<br>
(500khz?) I2C bus. At that frequency they would have minimal effect.<br>
<br>
On Thu, Nov 24, 2011 at 9:44 PM, Benjamin Deering<br>
<<a href="mailto:ben_deering@swissmail.org" target="_blank">ben_deering@swissmail.org</a> <mailto:<a href="mailto:ben_deering@swissmail.org" target="_blank">ben_deering@swissmail.<u></u>org</a>>> wrote:<br>
<br>
<br>
With the i2c devices removed, I get TTFF of around 1 minute in<br>
shr-core. It sounds like putting ferrite beads on SDA and SCL<br>
might help reduce EMI, so I will try that when I get a chance.<br>
<br>
Ben<br>
<br>
<br>
On 11/23/2011 05:06 PM, <a href="http://dmatthews.org" target="_blank">dmatthews.org</a> <<a href="http://dmatthews.org" target="_blank">http://dmatthews.org</a>> wrote:<br>
<br>
On Tue, 22 Nov 2011 21:20:16 -0500 <tel:16%20-0500><br>
Benjamin Deering<ben_deering@swissmail.<u></u>__org<br>
<mailto:<a href="mailto:ben_deering@swissmail.org" target="_blank">ben_deering@swissmail.<u></u>org</a>>> wrote:<br>
<br>
Hi Ben<br>
<br>
Not sure this is relevent to you, but I now have the fastest<br>
GPS fix I've ever had on the freerunner.<br>
<br>
QTMoko v35 and I put this in /etc/default/gpsd:-<br>
<br>
START_DAEMON="true"<br>
GPSD_OPTIONS=""<br>
DEVICES="/dev/ttySAC1"<br>
USBAUTO="false"<br>
GPSD_SOCKET="/var/run/gpsd.__<u></u>sock"<br>
<br>
Before doing this it was pretty poor - worse than earlier<br>
versions of qtmoko and much worse than every SHR I've tried.<br>
On a reasonably clear day I now reliably get a fix in under a<br>
minute, sometimes within a few seconds.<br>
<br>
The only other varying factor (doubtful relevence) is that I<br>
got pissed with QTMoko and to a lesser extent SHR foobarring<br>
the SD card, so I'm now running from the card instead of NAND<br>
and everything is pretty good<br>
<br>
<br>
<br>
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