[Ovmsdev] Poor wifi performance

Michael Balzer dexter at expeedo.de
Fri Jul 6 21:04:15 HKT 2018

I've had similar reports regarding poor wifi connectivity, and this seems to affect some modules more than others (or may be channel/frequency dependant?). One
user has just 1-2 bars AP wifi signal with the module placed ~ 50 cm away from the phone.

I also still get reports of spurious strange crashes, that mostly seem to be related to situations with poor wifi signal. Some crash backtraces just are
complete blank / null, and there is no crash report on the USB output for these before reboot.

Yesterday, Frank tried to perform some wifi scans. The first scan went fine, the second never returned, he had to power off the module. After reboot, all
successive scans worked.

Two users reported they occasionally cannot auth to the OVMS AP with the correct password, and they can then reconnect just by retrying for some minutes or by
connecting & disconnecting another client to the AP.

I already had a look at the wifi tx power configuration, it's at 100% by default.

This all feels like a) we need to change something about the antenna, and b) there are quite some bugs in the wifi blob.

Looking at https://github.com/espressif/esp32-wifi-lib/commits/master it seems there have been numerous wifi blob fixes lately. Last time I checked I still was
out of memory with the current esp-idf, I'll check again.


Am 06.07.2018 um 01:48 schrieb Stephen Casner:
> I find the wifi performance of OVMS v3 to be poor, and I'm wondering
> how it might be improved.  I have a mix of thoughts here.
> For both my own unit and that of Timothy Rodgers, wifi reception in
> our garages was unusable.  You can blame that on too much distance
> from the access point, but my iPhone and MacBook both access the wifi
> just fine from my garage.  The wifi antenna in the OVMS is probably
> smaller and its location within the metal framework around the car's
> firewall may impede radio transmission.  Perhaps it would be feasible
> to switch to an ESP32-WROVER-I with an external antenna to improve
> performance, but that would be a big deal.  If there is a transmit
> power adjustment, perhaps that could be increased?
> When Timothy parks his car next to his house, which is about 50 feet
> closer than the garage, then the wifi reception was good enough for
> the update to 3.1.008 to succeed.  But when he tries to connect with
> the browser, page updates often time out, so it is close to unusable.
> Perhaps we could improve usability by increasing the timeout in our
> javascript to allow more time for TCP to retransmit?
> For my own unit, I switched from AP+client to just client mode and at
> first it seemed that had improved the client performance.  But still
> the next day I had no access from the iPhone app.  When I connected to
> the console to find out why I saw that server v2 was repeatedly trying
> to connect and failing.  I'm presuming that the cause was poor wifi
> connectivity since I was also not able to reach the web server on the
> client address, although I have not proven that.  But since the client
> wifi was associated with the home AP and had an address, the OVMS
> network routing preferred the wifi and did not try to use the modem.
> For now I have resorted to turning off wifi.  I suggest that the
> network routing algorithm be enhanced to back off to use the modem if
> some number of attempts to connect to the server over wifi have
> failed.  The iPhone will do this for itself (there is a setting to
> enable this called Wi-Fi Assist).
> The behavior of repeated connection attempts and failures by server v2
> seems to induce a more serious failure after a while, perhaps due to
> some resource starvation.  At that point there is a failure message
> "mg_connect(api.openvehicles.com:6867) failed: cannot parse address"
> every time server v2 tries to connect.  I expect that is a bug that
> could be fixed.
> Lastly, since we may encounter situations where network communication
> is not working, we should facilitate access to the console.  When I
> was trying to help Timothy change a location radius setting remotely
> by phone and the web browser was timing out, I suggested that he find
> a micro-USB cable so he could connect to the console.  But then I
> realized he would not have any application on his laptop that would
> allow him to connect to the console.  Developers use "make monitor" in
> the software development cycle, but users won't have that tool.  I
> have my own program on the MacBook that I use as an alternative when I
> don't want to induce a reset when I connect.  But is there a simple
> program for Windows suitable for non-developer users that can connect
> to the OVMS console?
>                                                         -- Steve
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Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26

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