Re: I2C and GPS
can we have a picture of the final tweak please ? 2012/1/11 Benjamin Deering ben_deer...@swissmail.org Dusting off a very old thread... I have both of my sensors working and good gps performance now. 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 (http://www.jeepingben.net/**plog-content/thumbs/2010/** volkswagen/large/995-dscf2246.**jpghttp://www.jeepingben.net/plog-content/thumbs/2010/volkswagen/large/995-dscf2246.jpg). 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. Ben On 11/24/2011 11:36 AM, Alastair Johnson wrote: 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...@gmail.com mailto:dave...@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_deer...@swissmail.org mailto:ben_deering@swissmail.**orgben_deer...@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 Deeringben_deering@swissmail.**__org mailto:ben_deering@swissmail.**org ben_deer...@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 __**___ Openmoko community mailing list community@lists.openmoko.org mailto:community@lists.**openmoko.orgcommunity@lists.openmoko.org http://lists.openmoko.org/__**mailman/listinfo/communityhttp://lists.openmoko.org/__mailman/listinfo/community http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community __**_ Openmoko community mailing list community@lists.openmoko.org mailto:community@lists.**openmoko.orgcommunity@lists.openmoko.org http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community __**_ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community __**_ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
can we have a picture of the final tweak� please ? +1 yes please! I'm struggling to understand what you've done, but ity sounds like something I'd be very please to have. and by the way that stuff I wrote earlier about sdcards was garbage - it was a faulty card, not a problem with qtmoko or shr For me now first thoughts when I see an sdcard problem are that either the card is faulty or inherantly incompatible with the freerunner (and that seems very common) -- David Matthews m...@dmatthews.org ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
[cut] I don't know if anyone else is adding i2c sensors to their freerunner, but I thought this might be helpful. Very helpful. Can you provide schematics as a attachment to list, or as a link? -- Patryk LeadMan Benderz Linux Registered User #377521 () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
I promised myself that I wouldn't take my FR apart again until it was time to install the GTA04 board so I won't have pics of what I did this weekend, but I can share some other info. BMP085 barometer install pics: http://www.jeepingben.net/index.php?level=albumid=24 MLX90614 thermometer install pics: http://www.jeepingben.net/index.php?level=albumid=26 Adding i2c devices to a Freerunner is fairly easy. There are only 4 wires and as long as there aren't address conflicts, you can just keep adding more devices. Here is where you can find a picture of where to attach the wires: http://wiki.openmoko.org/wiki/Freerunner_Navigation_Board_v2#Installation The change I made this weekend was to stand an SMD resistor up vertically on the SCL test pad (If you look at the pictures I link above, that is where the orange wire attaches to the board) in the FR and solder it. I then attached the SCL wires for my 2 sensors to the top of the resistor. I used 4.7k ohm which is probably more than I should have used, but it works. I think 1K might make more sense, there was some mention of adding series resistors for long i2c circuits, though each of my SCL wires is 8 cm at the most. Sorry for the lack of pictures of the current state, but the way I crammed the BMP085 in is fragile and I don't want to break it. I hope my description along with the other pics makes it clear enough. As for schematics, i2c is just 4 wires VDD - voltage source on the AUX button GND - ground side of the clock battery (supercap in my case) SDA - SDA test pad near the debug connector SCL - 4.7k resistor -SCL test pad near the debug connector The reference implementation for the 2 sensors I installed was a little more complicated with pullup resistors and decoupling capacitors, but everything seems to work without them. Ben On 01/11/2012 07:46 AM, David Matthews wrote: can we have a picture of the final tweak� please ? +1 yes please! I'm struggling to understand what you've done, but ity sounds like something I'd be very please to have. and by the way that stuff I wrote earlier about sdcards was garbage - it was a faulty card, not a problem with qtmoko or shr For me now first thoughts when I see an sdcard problem are that either the card is faulty or inherantly incompatible with the freerunner (and that seems very common) ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
Dusting off a very old thread... I have both of my sensors working and good gps performance now. 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 (http://www.jeepingben.net/plog-content/thumbs/2010/volkswagen/large/995-dscf2246.jpg). 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. Ben On 11/24/2011 11:36 AM, Alastair Johnson wrote: 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...@gmail.com mailto:dave...@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_deer...@swissmail.org mailto:ben_deer...@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 Deeringben_deering@swissmail.__org mailto:ben_deer...@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 _ Openmoko community mailing list community@lists.openmoko.org mailto:community@lists.openmoko.org http://lists.openmoko.org/__mailman/listinfo/community http://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org mailto:community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
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 Deeringben_deer...@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 ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
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_deer...@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 Deeringben_deering@swissmail.**org ben_deer...@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 __**_ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
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...@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_deer...@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 Deeringben_deering@swissmail.**org ben_deer...@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 __**_ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/**mailman/listinfo/communityhttp://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
Re: I2C and GPS
On Tue, 22 Nov 2011 21:20:16 -0500 Benjamin Deering ben_deer...@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 -- David Matthews m...@dmatthews.org ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
I2C and GPS
For months now I have had poor performance with my Freerunner's GPS. The GPS problems did not seem to coincide with the two times I have opened my Freerunner to add I2C sensors. I have an infrared thermometer and a barometer. Lately I have missed the GPS enough to look into the issue more. After trying various things in software and messing with the GPS antenna, I started to look at my sensors. The reference schematics for both sensors call for a 100nf decoupling capacitor between ground and VDD. I looked around in my junk bin for some. All I could find were some huge (for the inside of a FR case) ceramic ones. They didn't seem to help. Using frameworkd.log with the log level turned up, I was able to watch the UBX packets as they came down and disconnecting SDA and SCL for both sensors gave an immediate improvement in GPS reception. I didn't notice a problem with reception when I first added the sensors. Was anything done in software that would make I2C cause more interference? Should I pursue the decoupling capacitors? Does it matter what kind if they are 100nf? Thanks for any ideas, Ben ___ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community
