<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi,<div><br><div><div>Am 18.11.2011 um 14:16 schrieb Boudewijn:</div><br class="Apple-interchange-newline"><blockquote type="cite"><span class="Apple-style-span" style="border-collapse: separate; font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div style="font-family: 'DejaVu Sans Mono'; font-size: 9pt; font-weight: 400; font-style: normal; "><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">On Friday 18 November 2011 11:13:00 Christoph Mair wrote:</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> On Fri, Nov 18, 2011 at 11:08 AM, Neil Jerram <<a href="mailto:neil@ossau.homelinux.net">neil@ossau.homelinux.net</a>> wrote:</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > On 18.11.2011 09:35, Neil Jerram wrote:</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >> On 17.11.2011 09:35, Christoph Mair wrote:</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >>> Maybe its possible to boot use a initramfs to test the GPS reception.</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >>> This would eliminate all activities on the mmc data lines.</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >> </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >> I'm willing to try this, but I don't understand how to implement your</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >> suggestion. Could you provide more detailed guidance? (Or just point</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> >> me to some existing reference.)</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > To be a bit more precise: I think I understand the idea of initramfs and</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > how to create one, but</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > (1) I can't see (looking at boot.txt) how I can tell u-boot to tell Linux</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > to use an initramfs</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > (2) I don't understand how this would eliminate MMC activity - because</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > wouldn't the kernel and initramfs still be being loaded from the SD card?</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> > (And I believe that MMC == SD, right?)</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> You're right. My thought was the following:</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> If the system is running from an initramfs the kernel won't touch the</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> SD card. If the rootfs is on the card it may uses it for whatever</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> reason (logging..).</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> Probably this could also be done with the u-boot test commands. If you</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> have access to the serial console, enter the u-boot command prompt and</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> type (from <a href="http://projects.goldelico.com/p/gta04-uboot/page/NewCommands">http://projects.goldelico.com/p/gta04-uboot/page/NewCommands</a>)</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> $ gps init</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> $ gps on</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> $ gps echo</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> </div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> This dumps the raw GPS records to your serial terminal. If you get a</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> fix with this setup it could be possible that some other component</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> which is active when linux is running disturbs the gps reception (i.e.</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">> mmc, display, ...)</div><p style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; "> </p><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">It may be worth a go of course, but I think Nikolaus meant more in general that if there's a (hardware) problem with an easy workaround, that does not mean that the cause to the symptoms is easily identified.</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; "><br></div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">In case of MMC: it's not only used for connecting SD/MMC cards, but for WIFI as well, isn't it? Of course the initramfs would have no need for WIFI either, and if ran from NAND it will exclude as many other factors as possible, but it's still prodding with a stick in the dark.</div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; "><br></div><div style="white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; text-indent: 0px; ">For wat it's worth, I just downloaded the new kernel and configs.. Who knows ;-)</div></div></span></blockquote><br></div><div>I spent the afternoon comparing several of the prototype GTA04 boards</div><div>and a GTA02. Using an external antenna glued with tape to the window's</div><div>glass (it is a little too cold to open the window and place the antenna</div><div>under open sky).</div><div><br></div><div>WIth the GTA02 I did receive approx. 5-7 satellites. So no problem.</div><div><br></div><div>Except one observation: putting the Freerunner (not the external</div><div>antenna!) on the closed display lid of a switched off eeePC</div><div>dropped the number of satellites quite abruptly to 0. Picking up</div><div>the Freerunner and moving away approx. 30 cm made it receive</div><div>again. This is a strange effect I had not at all expected that putting</div><div>a metal plate under the Freerunner (with battery and closed) </div><div>deteriorates the reception quality on an *external* antenna.</div><div><br></div><div>Now the GTA04 boards. They all appear to be quite deaf.</div><div>Independently of being powered from battery or from USB or both,</div><div>or having connected an internal, external antenna or both. And</div><div>no difference if we use the u-boot gps command or Linux.</div><div><br></div><div>After approx. 25 minutes one board (running Linux) did suddenly know the time.</div><div><br></div><div><div>Nov 18 18:52:27.411 cltest[723] NEMA: $GPRMC,002458.027,V,,,,,,,130806,,,N</div><div>Nov 18 18:52:28.348 cltest[723] NEMA: $GPGGA,185229.295,,,,,0,00,,,M,0.0,M,,0000</div><div>Nov 18 18:52:28.372 cltest[723] NEMA: $GPGSA,A,1,,,,,,,,,,,,,,,</div><div>Nov 18 18:52:28.418 cltest[723] NEMA: $GPRMC,185229.295,V,,,,,,,180806,,,N</div><div><br></div><div><div>And some seconds later it did know the date.</div><div><br></div></div><div>Nov 18 18:52:50.645 cltest[723] NEMA: $GPRMC,185251.295,V,,,,,,,180806,,,N</div></div><div><div><div>Nov 18 18:52:51.411 cltest[723] NEMA: $GPGGA,185252.295,,,,,0,00,,,M,0.0,M,,0000</div><div>Nov 18 18:52:51.434 cltest[723] NEMA: $GPGSA,A,1,,,,,,,,,,,,,,,</div><div>Nov 18 18:52:51.481 cltest[723] NEMA: $GPRMC,185252.295,V,,,,,,,181111,,,N</div></div></div><div><br></div><div>Again a little later:</div><div><br></div><div>Nov 18 18:53:10.450 cltest[723] NEMA: $GPGSV,3,1,12,04,89,179,26,20,56,046,,23,48,224,,27,37,090,</div><div><br></div><div>indicates that Satellite #04 had SNR of 26 dB at el=89 and az=179.</div><div><br></div><div>But that was the only satellite with a SNR different from 0 (empty string).</div><div><br></div><div>Does anyone know what a "reasonable" value of SNR should be?</div><div><br></div>So basically the GPS module is capable of receiving satellite data,</div><div>but appears to wear ear protectors :)</div><div><br></div><div>Therefore, I think we can already rule out the MMC (as it was on the GTA02),</div><div>because it is not running during the U-Boot gps command. And, it is</div><div>not a power supply issue nor something with big metal (battery)</div><div>near the GPS receiver.</div><div><br></div><div>This needs more study.</div><div><br></div><div>If all EA board owners could take the challenge and do some tests?</div><div>But please don't expect immediate results...</div><div><br></div><div>Nikolaus</div><div><br></div><div><br></div><div><br></div><div> </div></body></html>