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    It's sufficient to provide additional power to USB, but it needs to
    be a constant supply (the Twizy 12V port in the glove box is
    switched).<br>
    <br>
    <br>
    <div class="moz-cite-prefix">Am 17.05.2018 um 12:14 schrieb Michael
      Balzer:<br>
    </div>
    <blockquote type="cite"
      cite="mid:b7ca3e8e-6edf-5402-77ba-e55f0a803b75@expeedo.de">
      <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
      Is it sufficient to provide secondary power at the USB port or
      does the 12V supply needs to be detached?<br>
      <br>
      <br>
      <div class="moz-cite-prefix">Am 17.05.2018 um 12:00 schrieb Mark
        Webb-Johnson:<br>
      </div>
      <blockquote type="cite"
        cite="mid:F90CAE64-94B9-4A89-982F-4BCA63BEF079@webb-johnson.net">
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          charset=utf-8">
        <div>Other option I tried is to power from USB. But maybe not so
          easy in a Twizy?</div>
        <div><br>
        </div>
        <div>I should have new chips early next week. Arranging now.</div>
        <div><br>
        </div>
        <div>Regards, Mark</div>
        <div><br>
          On 17 May 2018, at 5:48 PM, Michael Balzer <<a
            href="mailto:dexter@expeedo.de" moz-do-not-send="true">dexter@expeedo.de</a>>
          wrote:<br>
          <br>
        </div>
        <blockquote type="cite">
          <div>
            <meta http-equiv="Content-Type" content="text/html;
              charset=utf-8">
            Wow. Confirmed, speedup is at least factor 5.<br>
            <br>
            And better yet, the fsync() overhead is reduced from ~50 ms
            to < 10 ms as well, the performance impact of SD logging
            is now fully acceptable for every day use.<br>
            <br>
            All of my beta testers use SD cards to provide debug logs.
            Some also have been doing CAN logging, which helped debug
            some timing issues.<br>
            <br>
            I'll need another 3.1 module anyway, but the testers will
            most likely want to continue using their modules. I'll
            forward your rework offer and the info on how to solve this
            themselves if they're capable of doing micro-soldering.<br>
            <br>
            Regards,<br>
            Michael<br>
            <br>
            <br>
            <div class="moz-cite-prefix">Am 17.05.2018 um 10:40 schrieb
              Mark Webb-Johnson:<br>
            </div>
            <blockquote type="cite"
              cite="mid:C33A2DBF-2A19-4423-B3CC-D38F3534A1FA@webb-johnson.net">
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                charset=utf-8">
              <div class=""><br class="">
              </div>
              It is a lot faster when working correctly. To me, it seems
              much more than 25%. Maybe four or five times faster?
              <div class=""><br class="">
              </div>
              <div class="">You can try:</div>
              <blockquote style="margin: 0 0 0 40px; border: none;
                padding: 0px;" class="">
                <div class="">config set sdcard maxfreq.khz 20000</div>
              </blockquote>
              <div class="">
                <div>then reboot and power from USB. Then try your speed
                  test. Perhaps vfs cp from SD to SD to test?</div>
                <div><br class="">
                </div>
                <div>Regards, Mark.</div>
                <div><br class="">
                </div>
                <div>
                  <blockquote type="cite" class="">
                    <div class="">On 17 May 2018, at 4:15 PM, Michael
                      Balzer <<a href="mailto:dexter@expeedo.de"
                        class="" moz-do-not-send="true">dexter@expeedo.de</a>>
                      wrote:</div>
                    <br class="Apple-interchange-newline">
                    <div class="">
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                        content="text/html; charset=utf-8" class="">
                      <div text="#000000" bgcolor="#FFFFFF" class="">
                        Thanks for the analysis and solution!<br
                          class="">
                        <br class="">
                        What kind of speedup is achievable by replacing
                        the cp2102? Is it just linear 16 → 20 MHz = 25%?<br
                          class="">
                        <br class="">
                        Or does this also solve hidden retransmission
                        issues?<br class="">
                        <br class="">
                        <br class="">
                        <tt class=""><a class="moz-txt-link-abbreviated"
href="mailto:balzer@leela:%7E/esp/Open-Vehicle-Monitoring-System-3/vehicle/OVMS.V3"
                            moz-do-not-send="true">balzer@leela:~/esp/Open-Vehicle-Monitoring-System-3/vehicle/OVMS.V3</a>>
                          time ssh dexze85.local "vfs ls /sd/logs"</tt><tt
                          class=""><br class="">
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                        </tt><tt class="">user    0m0.018s</tt><tt
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                        <div class="moz-cite-prefix">Am 17.05.2018 um
                          04:22 schrieb Mark Webb-Johnson:<br class="">
                        </div>
                        <blockquote type="cite"
                          cite="mid:56C111E5-AC24-4BE2-8800-61616261D757@webb-johnson.net"
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                            <div class="">Good grief. A year into this,
                              and still writing about SD CARD issues
                              with ESP32. If I could get into a room
                              with the engineer who decided to share
                              boot strapping pins with SDCARD pins, and
                              to hard wire the SDIO controller to
                              specific pins, I would literally try to
                              slap some sense into him.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">The China guys and I have been
                              struggling for the past couple of months
                              trying to work out why we can’t get as
                              much speed out of the SD CARD as we
                              wanted. If we raise the speed to the
                              normal 20MHz, we randomly get errors
                              (timeouts, checksums, etc). It looked like
                              interference on the bus lines, but scoping
                              those we can’t find any. Dropping the
                              speed to 16MHz works around the issue, but
                              SD CARD accesses are slow.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">Then, we worked out it wasn’t
                              random. It was based on whether we were
                              powering from USB or external 12V. On the
                              bench it works fine. In the car the
                              problem appears. Simply put, if the USB
                              was plugged in the ‘interference’
                              disappeared. If USB was unplugged, it came
                              back. USB + external 12V combination also
                              didn’t suffer from the issue, so the
                              problem is not coming from the 12v side.
                              The issue often appeared on only the
                              second test of SD CARD, not the first. We
                              didn’t see this problem on either the v3.0
                              developer modules, or v3.1 prototypes.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">We looked at the capacitors
                              and pull-up resistors on that side of the
                              circuit, without success. Whatever we did
                              made little difference (or randomly
                              changed things for the better/worse). We
                              thought maybe ground-line interference,
                              but nope. We spent some time looking at
                              C20, C22, C23 to see if the manufacturers
                              had messed up the component values - they
                              hadn’t.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">Anyway, to cut a long story
                              short, we finally found the culprit. The
                              CP2102 chip itself.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">We’d already had to change the
                              power supply design early on in the
                              project to cope with a bug in CP2102 not
                              correctly handling USB host disconnect and
                              not properly going into suspend mode (to
                              reduce power consumption of cp2101 circuit
                              when usb was disconnected) - our current
                              design completely powers down the cp2102
                              chip when the USB cable is disconnected.
                              Michael Stegen had previously warned me
                              about clones of this chip (see <a
                                href="https://wiki.sha2017.org/w/Projects:Badge"
                                class="" moz-do-not-send="true">https://wiki.sha2017.org/w/Projects:Badge</a>
                              and what they went through), and we had
                              added the extra resistor already to cope
                              with that eventuality. But, from what we
                              can tell this is not a clone part issue.
                              Here is what we found:</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">
                              <ol class="MailOutline">
                                <li class="">OVMS v3.0 and early v3.1
                                  prototypes use CP2102 v1412+. For that
                                  chip, when the USB cable is
                                  disconnected, CSL-TXD is 3.3v.</li>
                                <li class="">OVMS v3.1 first production
                                  batch use a newer CP2102 v1708+. For
                                  that chip, when the USB cable is
                                  disconnected, CSL-TXD is pulled down
                                  to 0.78v.</li>
                                <li class="">We have replaced the cp2102
                                  on a v3.1 first production module with
                                  v1412+, and SD CARD resumes normal
                                  operation (even with usb
                                  disconnected).</li>
                                <li class="">The version number seems to
                                  be a date code. YYWW (year, week), I
                                  guess.</li>
                                <li class="">We have absolutely no idea
                                  why this would be affecting the SD
                                  CARD performance or interference.
                                  Somehow, that CSL-TXD line is going
                                  through the ESP32 chip and affecting
                                  the  SDIO controller (perhaps related
                                  to the bootstrapping pins dual use).
                                  The interference we see is inside the
                                  ESP32, not on the lines going from
                                  ESP32 to the SDCARD (which is why we
                                  couldn’t see it on the scope).</li>
                              </ol>
                            </div>
                            <div class=""><br class="">
                            </div>
                            <div class="">I tried shutting down the pins
                              on the ESP32 for CSL-TXD and CSL-RXD, to
                              see if I could work around the problem in
                              firmware, but couldn’t get it to work.
                              There is no way of knowing whether the USB
                              is connected, and even if we did know,
                              setting CSL-TXD and CSL-RXD pins to output
                              mode, or float, doesn’t seem to make any
                              difference.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">The good news is that we’ve at
                              least identified the problem. We are (a)
                              checking the revision of cp2102 chip in
                              the upcoming production batch, and (b)
                              changing QC procedures to set SD CARD bus
                              speed to default (20MHz) and randomly test
                              modules twice on 12V power. Latest
                              production batch is now using v1742+, and
                              that has been tested as working. Going
                              forward, we can resolve this.</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">As for the first production
                              batch units, they are what they are. For
                              normal SD CARD operation (copying files,
                              flashing firmware, etc), it makes little
                              difference. I guess most users don’t even
                              have an SD CARD inserted. The speed
                              limitation really only becomes an issue if
                              you are trying to log lots of data to SD
                              CARD (such as CAN bus dumps). If the USB
                              is connected, you can 'config set sdcard
                              maxfreq.khz 20000’ and it will work
                              faster. The CP2102 chip can be changed,
                              and I’ll do that for anyone that needs it.
                              I’m asking China to send me some from the
                              latest production batch that we know
                              works. Replacement is relatively
                              straightforward, but involves
                              micro-soldering (the cp2102 is a surface
                              mount chip, very small footprint, with
                              lots of other components near it on the
                              board).</div>
                            <div class=""><br class="">
                            </div>
                            <div class="">Regards, Mark.</div>
                            <div class=""><br class="">
                            </div>
                          </div>
                          <br class="">
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