<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">To put in code the two alternative approaches being considered:<div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class="">enum</div><div class="">{</div><div class="">other,</div><div class="">kilometers,</div><div class="">miles,</div><div class="">celcius,</div><div class="">fahrenheit,</div><div class="">kpa,</div><div class="">psi,</div><div class="">percentage</div><div class="">} unit_t;</div></blockquote><br class=""><div class=""><ol class="MailOutline"><li class="">Everything metric<br class=""><br class="">OvmsMetric:<br class=""> unit_t m_unit;<br class=""> unit_t GetUnit();<br class=""> std::string AsStringConverted(unit_t conversion);<br class=""><br class=""></li><li class="">Unit with the metric<br class=""><br class="">OvmsMetric:<br class=""> unit_t m_unit;<br class=""> unit_t GetUnit();<br class=""> std::string AsStringConverted(unit_t conversion);<br class=""> void SetValue(std::string value, unit_t unit);<br class="">etc</li></ol></div><div class=""><br class=""></div><div class="">The difference is that with [1] m_unit is always the metric unit, and with [2] m_unit is the unit set when the value is stored. With [1], the vehicle module will perform any incoming conversion to metric, while with [2], the vehicle just stores the value and unit together (with conversion being performed, if necessary, on retrieval).</div><div class=""><br class=""></div><div class="">The first is simpler, but does suffer from the double conversion issue in some cases. The second avoids that, at the expense of complexity.</div><div class=""><br class=""></div><div class="">How we present this to apps is really irrelevant (or the decision at least can be put off to later as that is a v3 protocol decision). For v2 protocol, we have to present as per the v2 protocol specification.</div><div class=""><br class=""></div><div class="">On review, I think my personal preference is really for [2]. I understand it is more complex, but it is quite elegant. Conversions are only done when absolutely necessary. Let’s look at an extreme example of a vehicle producing miles data, and an app requesting miles. With [1], the vehicle would convert miles->km and store in the metric, then ovms_server_v2 would convert km->miles and send it out. With [2], the vehicles stores the (value,”miles”) in the metric, and ovms_server_v2 reads value back out (using “miles” as a selector for the value). If a user sets his units to “km”, and does a “metric list”, with [2], the metric itself converts miles->km for the display. So, [2] does complicate it, but all that complication is hidden in the standardised metric system.</div><div class=""><br class=""></div><div class="">Regards, Mark.</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 26 Oct 2017, at 9:51 AM, Mark Webb-Johnson <<a href="mailto:mark@webb-johnson.net" class="">mark@webb-johnson.net</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">I did a quick review of the way things were done in OVMS v2. Some notes:</div><div class=""><br class=""></div><div class="">The OVMS v2 protocol specified:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">Car Environment message 0x44 “D"<br class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Temperature of the PEM (celcius)</div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Temperature of the Motor (celcius)</div></div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Temperature of the Battery (celcius)</div></div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Car trip meter (in 1/10th of a distance unit)</div></div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Car odometer (in 1/10th of a distance unit)</div></div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Car speed (in distance units per hour)</div></div><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Ambient Temperature (in Celcius)</div></div></li><li class="">Car state message 0x53 “S”<br class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Units ("M" for miles, "K" for kilometers)<br class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Ideal range<br class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• Estimated range</div></div></div></li><li class="">Registered parameter #2<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>• Miles / Kilometer flag</li></ul></div><div class=""><br class=""></div><div class="">The OVMS v2 net_msg code did some conversions:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">car_tpem is always stored in Celcius, and always sent as such</li><li class="">car_tmotor is always stored in Celcius, and always sent as such</li><li class="">car_tbattery is always stored in Celcius, and always sent as such</li><li class="">car_trip is stored in Miles, so a KmFromMi() conversion is done if units were “K”</li><li class="">car_odometer is stored in Miles, so a KmFromMi() conversion is done if units were “K”</li><li class="">car_speed is stored in user unit, and sent as such</li><li class="">car_ambient_temp is always stored in Celcius, and always sent as such</li><li class="">Units is stored as a parameter, and sent as such</li><li class="">car_idealrange is stored in Miles, so a KmFromMi() conversion is done if units were “K”</li><li class="">car_estrange is stored in Miles, so a KmFromMi() conversion is done if units were “K”</li><li class="">tpms is stored in raw (Tesla) format, and sent as PSI and Celcius</li></ul></div><div class=""><br class=""></div><div class="">I did some quick checks against the OVMS v2 vehicle_*.c code. Here are some notes:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">Kia Soul: Seems to have distances in metric, and uses MiFromKm() when storing to car_*. Temperatures in celcius, so no conversion necessary.</li><li class="">Mitsubishi iMiev: MiFromKm() for distances. Temperatures in celcius, so no conversion necessary.</li><li class="">Tesla Roadster: Miles for distances, Celcius for temperatures, so no conversions necessary (surprise, surprise, as OVMS v2 car model based on this car).</li><li class="">Nissan Leaf: MiFromKm() for distances. Temperatures in celcius, so no conversion necessary.</li><li class="">Twizy: MiFromKm() for distances. Temperatures in celcius, so no conversion necessary.</li><li class="">Renault Zoe: MiFromKm() for distances. Seemingly no temperature support.</li></ul></div><div class=""><br class=""></div><div class="">I then looked at the OBDII standard. Here are the notes from that:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">Temperatures are stored and transmitted in Celcius</li><li class="">Pressures are stored and transmitted in Pa / kPa</li><li class="">Distances are stored and transmitted in Km</li><li class="">Time is stored and transmitted in Seconds</li></ul></div><div class=""><br class=""></div><div class="">I looked at the Apps.</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">Configurable for temperatures: car chooses / celcius / fahrenheit</li><li class="">Configurable for distances: car chooses / miles / kilometers</li><li class="">No configuration for pressures</li></ul></div><div class=""><br class=""></div><div class="">Overall, I would conclude:</div><div class=""><br class=""></div><div class=""><ul class="MailOutline"><li class="">The OVMS v2 protocol is kind of messy, not symmetric. It does conversions in some place, but in others leaves it up to the App.</li><li class="">It seems that almost all the vehicles use metric units</li><li class="">OBDII uses metric units</li><li class="">We need to maintain compatibility with OVMS v2 protocol, but can do things differently for v3 protocol</li></ul></div><div class=""><br class=""></div><div class="">I suggest the following:</div><div class=""><br class=""></div><div class=""><ol class="MailOutline"><li class="">The Metrics use metric units for their internal storage (sic).</li><li class="">We add units labels to the metrics. This can be used (a) as a nice display (SOC: 10% vs 10), and (b) as the basis for conversion support at the metric level.</li><li class="">We add units parameters to the configuration storage (for pressure, temperature, distance).</li><li class="">We make the ovms_server_v2 convert to the v2 protocol standard</li></ol></div><div class=""><br class=""></div><div class="">Doing it that way means that most vehicles will store in their native format (metric) - only Tesla Roadster will incur a Miles->KM->Miles penalty. Using ‘float’ to some extent mitigates this.</div><div class=""><br class=""></div><div class="">The alternative (storing the unit with the metric, and having it passes whenever we set/read the metric) is much more complex and seemingly only required for one particular vehicle (ignoring the temporary issue of v2 protocol, until we roll out v3 protocol and apps).</div><div class=""><br class=""></div><div class="">I do think that whatever we decide, it needs to be decided now. We are converting the vehicle modules over, and doing this now is much simpler than trying to re-work it later.</div><div class=""><br class=""></div><div class="">Regards, Mark.</div><div class=""><br class=""></div><blockquote type="cite" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">Really not a fan of this, as the app may not even know what kind of</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">vehicle is being used (an attached HUD, for example). If there's a</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">function in the metric object that does the conversion to make it</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">transparent, I suppose that could work. But I'd really prefer to have</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">at least the standard metrics table be vehicle-independent, and in</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">standard units. The OBDII spec assumes this, and the devices all have</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">Metric / Imperial mode switches included. For common items that may be</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">missing from a particular vehicle (e.g. motor RPM on the Roadster), the</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">vehicle code that populates the metrics table should derive them from</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">what is available. For the Roadster example, motor RPM is basically</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">vehicle speed times 70, so when receiving a speed CAN frame, both the</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">v.p.speed and v.p.rpm (new metric, please?) would be updated.</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">If there are metrics that don't apply to multiple vehicles, and don't</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">fit into the standard ones, they can certainly be in vehicle-specific</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">units. Best to have a separate table for them, I think, with the items</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">prefaced by the 2-letter vehicle name. I can certainly deal with having</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">a table name as part of the PID remapping scheme. But, please, not on a</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">per metric basis.</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">The vehicle-specific use can also be aided by scripting some of the</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">conversion. Still working on how that can be done. But again, we</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">shouldn't need to load in a whole library of vehicle-specific scripts</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">just to handle the common parameters (speed, SoC, etc.).</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">My $.02,</span><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><br style="font-family: Menlo-Regular; font-size: 14px;" class=""><span style="font-family: Menlo-Regular; font-size: 14px;" class="">Greg</span></blockquote><div class=""><font face="Menlo-Regular" class=""><span style="font-size: 14px;" class=""><br class=""></span></font><div class=""><blockquote type="cite" class=""><div class="">On 25 Oct 2017, at 12:26 PM, HONDA S-2000 <<a href="mailto:s2000@audiobanshee.com" class="">s2000@audiobanshee.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I like the concept of storing vehicle units in the module and letting the app sort out the conversions. Theoretically, this allows for alternate app front ends that might do “something” with the additional information in the vehicle units that might be lost in translation (conversion). But, I am a nerd with a bias towards low-level details, and that might not be the best. :-)<br class=""><br class="">Obviously, the down side is that each additional vehicle unit adds to the code in the app. My usual assumption is that there’s more room in a front end application for these sorts of things, as opposed to the embedded side. To contradict myself, though, it seems that we’re allowing for the embedded firmware to be compiled for a single vehicle, meaning that none of the code needs to carry around unused conversions.<br class=""><br class="">Stepping away from my technical focus (where I might be interested in the exact vehicle units for, e.g., torque on my roadster), perhaps it would be better to design around the typical user, who will either be interested in miles or kilometers, foot-pounds or Newton-meters, and basically just English versus metric. In that case, maybe the embedded firmware could have a meta parameter to select English versus metric, and then all communications with the app would be in those units. The down side to this idea is that the embedded firmware would need to be capable of two different conversions for potentially every metric, assuming that every electric vehicle is available in multiple countries, both metric and English.<br class=""><br class="">Sorry to throw a jumbled set of ideas at the problem, but I wanted to share my thoughts.<br class=""><br class="">Brian<br class=""><br class=""><br class="">On Oct 24, 2017, at 1:08 PM, Michael Balzer <<a href="mailto:dexter@expeedo.de" class="">dexter@expeedo.de</a>> wrote:<br class=""><blockquote type="cite" class="">I've done the int to float changes and the temperature naming.<br class=""><br class="">Not sure about the best way to solve the units problem yet, but I guess<br class="">we can start with storing in vehicle units and add the conversion later on.<br class=""><br class="">Regards,<br class="">Michael<br class=""><br class="">Am 24.10.2017 um 04:46 schrieb Mark Webb-Johnson:<br class=""><blockquote type="cite" class="">Tough questions. Answers/comments inline.<br class=""><br class=""><blockquote type="cite" class="">On 23 Oct 2017, at 9:33 PM, Michael Balzer <<a href="mailto:dexter@expeedo.de" class="">dexter@expeedo.de</a>> wrote:<br class=""><br class="">Trying to catch up…<br class=""><br class=""><br class="">a) I'd love to get rid of those km→miles→km conversions in V3.<br class=""><br class="">How about introducing a metric "v.units" instead to hold the units used<br class="">by the vehicle, and make conversions at the user level if necessary?<br class=""></blockquote>I don’t have a good answer for this. I thought to just store all the metrics in ‘metric’ (celcius, kilometers, etc), and let the apps deal with it (as they do now). But, as you say, that does lead to the problem of km->miles->km, etc.<br class=""><br class="">An alternative is to store a ‘units’ with the metric, and have the metric deal with presentation conversion upon retrieval. That reduces the number of conversions.<br class=""><br class="">In general, having this done in the module seems to make more sense than doing it in the apps.<br class=""><br class=""><blockquote type="cite" class="">b) Regarding the standard metrics currently defined, I'd need to<br class="">introduce own copies again for higher precision. I.e. SOC, SOH, speed<br class="">and ranges all are integers now, and some more I'd like to be able to<br class="">set at higher precision.<br class=""><br class="">How about making all these be floats now? I.e. everything that can<br class="">require more than integer precision.<br class=""><br class="">The server_v2 can output the values as integers for v2 client compatibility.<br class=""></blockquote>OK.<br class=""><br class=""><blockquote type="cite" class="">c) I haven't seen a recommendation on naming vehicle specific metrics.<br class="">My proposal: use the vehicle code as the prefix, then try to reuse<br class="">similar paths from the standard metrics, adding detail as necessary.<br class=""><br class="">For example, the vehicle module version on the Twizy ("RT") is<br class="">"rt.m.version", and for the min & max battery voltage I've got<br class="">"rt.v.b.voltage.min" & "rt.v.b.voltage.max".<br class=""><br class="">OVMS > metrics list rt.<br class="">rt.m.version 1.0.0 Oct 23 2017 11:45:31<br class="">rt.v.b.soc <br class="">rt.v.b.temp.m1 <br class="">rt.v.b.temp.m2 <br class="">rt.v.b.temp.m3 <br class="">rt.v.b.temp.m4 <br class="">rt.v.b.temp.m5 <br class="">rt.v.b.temp.m6 <br class="">rt.v.b.temp.m7 <br class="">rt.v.b.voltage.max 0<br class="">rt.v.b.voltage.min 0<br class=""><br class="">That way a path component can be used to list all related metrics:<br class=""><br class="">OVMS > metrics list b.voltage<br class="">rt.v.b.voltage.max 0<br class="">rt.v.b.voltage.min 0<br class="">v.b.voltage <br class=""></blockquote>Ok, but I would suggest an ‘x.’ prefix (seems to match many Internet standards, such as X- headers, etc).<br class=""><br class="">So: x.rt.v.b.voltage.max, etc.<br class=""><br class=""><blockquote type="cite" class="">d) I think most of the temperature metrics have wrong names:<br class=""><br class="">v.b.temp.ambient <br class="">v.b.temp.battery <br class="">v.b.temp.charger <br class="">v.b.temp.motor <br class="">v.b.temp.pem <br class=""><br class="">…as "b." should be reserved for "battery".<br class=""><br class="">How about…<br class=""><br class="">v.e.temp<br class="">v.b.temp<br class="">v.c.temp<br class="">v.m.temp<br class="">v.i.temp<br class=""><br class="">…introducing "m." for motor and "i." for inverter?<br class=""></blockquote>OK.<br class=""><br class=""><blockquote type="cite" class="">Regards,<br class="">Michael<br class=""></blockquote></blockquote></blockquote><br class="">_______________________________________________<br class="">OvmsDev mailing list<br class=""><a href="mailto:OvmsDev@lists.teslaclub.hk" class="">OvmsDev@lists.teslaclub.hk</a><br class=""><a href="http://lists.teslaclub.hk/mailman/listinfo/ovmsdev" class="">http://lists.teslaclub.hk/mailman/listinfo/ovmsdev</a><br class=""></div></div></blockquote></div><br class=""></div></div></div></blockquote></div><br class=""></div></body></html>