[Ovmsdev] Ioniq 5 - Pushing up some prerequisite changes to components/vehicles
Michael Balzer
dexter at expeedo.de
Sat Oct 29 20:15:49 HKT 2022
Michael,
please don't change existing vehicle code for personal code style
reasons. The existing data extraction methods have been working and will
continue to work. By adding your utilities to the framework, we're
giving everyone interested the opportunity to consider using these, we
don't force them to do.
Regarding your combined data extraction & metric setting utility, from
my experience this won't be applicable in many (most) cases, or would
need quite a lot of extra features exceeding a simple scaling.
Applications often need or want to change metrics only indirectly after
processing the raw data read from the bus, often in combination with
other readings and/or delayed. Validity checks also need to be done in a
broad variety, often with side conditions.
A good approach is to first define & refine your generalized methods
locally in your component. Keep an eye on the existing method
signatures, so once you're happy with them it's easy to move them into
the framework. That way you'll avoid having to break compatibility for
other developers possibly already using an early release of your method.
Regards,
Michael
Am 27.10.22 um 09:36 schrieb Michael Geddes:
> While I'm still happy with the base data extraction tools, I'm
> wondering if some more direct tools would be better.
>
> For example some methods on the Base vehicle that takes a buffer, a
> byte index and template byte count a Metric object and a multiplier..
> That will conditionally set the metric if the data is within bounds.
>
> Or methods on the metrics themselves that has similar results.
>
> I notice that index by 4 bit 'nibbles' is also a Thing That Is Done.
>
> I'm happy to implement that if there's appetite for it... And possibly
> look at a few Vehicles to switch to that
>
>
> Michael
>
> On Mon, 24 Oct 2022, 1:26 pm Michael Geddes,
> <frog at bunyip.wheelycreek.net> wrote:
>
> Ok - so I've pared down my requirements on the BMS module to the
> ability to be able to cap the # of Voltages/Temperatures at a
> lower (only) value than initialised at.
> This means that the code to create the averages etc is just pulled
> out to a private function here:
> https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/753
>
>
> This P/R request adds the buffer extraction tools (with 32bit
> length) to ovms utils.
>
> https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/754
>
> //.ichael
>
> On Sun, 23 Oct 2022 at 17:38, Michael Geddes
> <frog at bunyip.wheelycreek.net> wrote:
>
> Thanks Michael,
>
> I have taken it in, and I'll use std::string in poll once
> code. I guess it might make sense to convert everything else
> to std::string. It wouldn't be a big task.
>
> I had just taken out that commit and reworked anyway, and now
> that you say it's not the best way of doing things, I'm even
> happier I made that choice, as I had intended to possibly make
> more use of it and won't now. At the moment I'm using it to
> get the VIN (snipped) where I'll try a couple of times only,
> rather than continually poll for it.
> Hmm... yea - I guess I could do some dynamically created poll
> table. Will definitely consider that.
>
> Further comments inline below:
>
> On Sun, 23 Oct 2022 at 16:15, Michael Balzer
> <dexter at expeedo.de> wrote:
>
> Michael,
>
> what I really dislike about your change is that it adds
> complexity to the underlying function just to fulfill an
> -- in my eyes more academic -- type style choice: having
> to handle multiple buffer pointers just to provide
> different typing approaches is bad. You could introduce a
> new construct to provide a single polymorphic pointer, but
> that again adds complexity.
>
> Agreed, std::string is a bit type-sloppy in depending on
> char being unsigned 8 bit, but that's all to consider, and
> can easily be enforced if ever necessary.
>
> On the plus side, std::string has far better library
> support, better interoperability (see our use cases), and
> small string optimization, which is especially useful for
> our platform, as most poll requests and responses easily
> fit into the initial capacity, normally eliminating the
> need for heap allocations.
>
> So, besides the type independency, I think std::vector has
> no advantage here.
>
>
> There's another thing I'd like to address: it seems you're
> planning to use single polls extensively?
>
> If so, please don't, unless you're also going to do a full
> rewrite of the poller towards a job/worker service task
> architecture (that's a very old todo).
>
> The single poll utility is really meant for sparse/manual
> polls outside the normal polling scheme. See my comment on
> the method:
>
> * PollSingleRequest: perform *prioritized synchronous*
> single OBD2/UDS request
> * Pass a full OBD2/UDS request (mode/type, PID,
> additional payload).
> * The request is sent immediately, *aborting a running
> poll list request*. The previous
> * poller state is automatically restored after the
> request has been performed, but
> * *without any guarantee for repetition or omission of an
> aborted poll*.
>
> This was really meant more for user/script use than for
> standard vehicle polls, though it's OK to use it, where
> applicable, with caution.
>
> For all standard polling, install a PID list. You can vary
> a list by the poll state, and you can switch lists if
> necessary. PID lists can easily be generated dynamically,
> see the VWUP code for an example.
>
>
> The place for general CAN utility methods is the
> components/can/src/canutils module, general utility
> methods go into the main/ovms_utils module.
>
> Ahh.. cool.
>
>
> Regarding CAN buffer data extraction, there are currently
> probably as many approaches as there are vehicle modules.
> Certainly would be nice to have some standard way here,
> but won't be simple to rework the existing vehicle adaptors.
>
> The template approach is a nice one for a general
> solution, but keep in mind not every vehicle will use big
> endian encoding, in some cases not even consistently
> throughout the installed devices.
>
>
> I had already implemented little-endian and big-endian
> versions of the data extract. I will now explicitly mark all
> of them.
>
>
> To be really general, your byte addressing needs to
> support more than 256 bytes in the buffer.
>
> Consider that fixed.
>
> Your templates also lack bit masking and shifting. Some
> devices use packed structs with odd sized bit fields. The
> DBC engine has support for all this, but not generalized.
> I remember Mark getting a headache from this…
>
> I have a get_bit<>() function and so I would propose it be
> implemented in a similar way... ie exract the byte first, then
> get the bits.
> Something like: extract_int<1,2>(byte) --> Extract bits len 2
> starting from bit 1. We can easily sign-extend that too.
>
> Regards,
> Michael
>
>
> Am 23.10.22 um 02:23 schrieb Michael Geddes:
>> Hi Michael,
>>
>> Just wanted to say that if you override my objections on
>> the std::vector<unit8_t> in the single poll code then I'm
>> fine with that, I recognised that it's absolutely your
>> call and that bit has a small impact on my code so far.
>> I can even add versions of the extraction functions that
>> use std::string if you want (they would just be inline
>> template wrappers around common code anyway so zero
>> compiled cost).
>>
>> Also: Is there a better place to put those templated
>> functions? A version of my sign_extend function is
>> already being proposed being used here:
>> https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/pull/736
>> - it would be good if both versions of this function were
>> available in a single place. (There's
>> sign_extend<UINT, INT>(int_value, sign_bit) and
>> sign_extend<UINT, INT, SIGNBIT>(int_value) - so they
>> should work fine as overloaded template functions).
>>
>> I would consider also whether I use std::string in my own
>> code where I'm extracting my data out of complete ISOTP
>> poll results. Up to you. That has slightly more impact,
>> but the code change is pretty easy.
>>
>> //.ichael
>>
>> On Sat, 22 Oct 2022 at 07:56, Michael Geddes
>> <frog at bunyip.wheelycreek.net> wrote:
>>
>> Thanks Michael,
>>
>> I had already created my commits under the assumption
>> that you would prefer the general changes separate
>> from the vehicle-specific commits.
>>
>> I have created 3 pull requests so far.
>> 1) the bug - that's a no-brainer.
>> 2) 'finalisation' of temperatures and voltages.
>> (Draft, see below)
>> 3) vector poll. This is more a point of discussion
>> (see below)
>>
>> A couple of the next bugs are kind of dependent on
>> the second, so I'll wait until I get that sorted out.
>>
>> More comments below.
>>
>> On Fri, 21 Oct 2022 at 23:31, Michael Balzer
>> <dexter at expeedo.de> wrote:
>>
>> Michael,
>>
>> Am 19.10.22 um 07:26 schrieb Michael Geddes:
>> > Hi all,
>> >
>> > I have 6 commits that I would _like_ to get
>> pushed up that are changes
>> > to components/vehicles required for my Ioniq 5
>> changes to work.
>> >
>> > I can push them all up in a single merge
>> request for review, or
>> > separate them out into bits. Some of them I am
>> expecting there to be
>> > opinions on. I'm prepared to simplify some, and
>> one in particular has
>> > grounds for nixing. I think it's a good change,
>> but I could manage
>> > without it.
>>
>> Please keep PRs as small as possible, focusing on
>> one specific
>> modification / addition at a time. That way,
>> every merge commit can
>> easily be reverted if necessary, and changes can
>> be followed and
>> referred to easily. Especially keep framework
>> changes separate from
>> vehicle specific ones.
>>
>> It's also OK to open the PRs tagged as drafts /
>> work in progress, that
>> helps in commenting on certain parts and tracing
>> refinements. Create one
>> branch for each PR, pushing new commits into the
>> branch will
>> automatically update any open PR created from it.
>>
>> Ooh. That's useful. It's been a while since I've used
>> github for collab. Switched the battery sensor P/R
>> over to a draft.
>>
>>
>> >
>> > One is a simple bugfix - a literal
>> one-character change:
>> > void OvmsVehicle::BmsRestartCellTemperatures()
>> > {
>> > m_bms_bitset_t.clear();
>> > - m_bms_bitset_v.resize(m_bms_readings_t);
>> > + m_bms_bitset_t.resize(m_bms_readings_t);
>> > m_bms_bitset_ct = 0;
>> > }
>>
>> Obviously a copy & paste bug, nice find. I wonder
>> how that could slip
>> through without causing crashes, as there are
>> more voltages than
>> temperatures in most packs.
>>
>> Please don't hesitate with opening PRs even for
>> single fixes like this,
>> the sooner we include them, the better.
>>
>>
>> Yep. Done and understood.
>>
>>
>>
>> >
>> > On is a simple code readability change. Using
>> an enum instead of magic
>> > status values for m_bms_talerts. Simple
>> enough, but I'm prepared to
>> > simplify that to a standard enum or get rid of it.
>>
>> The magic values are simply alert levels, but go
>> ahead, readability is a
>> good goal.
>>
>> I'll include it once the Battery Cell code is finalised.
>>
>> >
>> > There's some battery related ones where I want
>> to be able to not quite
>> > know the number of cells from the start and let
>> the OBD responses specify.
>>
>> Dynamic pack layout reconfiguration is no issue,
>> I've done that on the
>> Twizy (look for comments "update pack layout" or
>> calls to
>> BmsSetCellArrangement*).
>>
>> BmsSetCellArrangement does clear all the values...
>> which is probably the main thing I was trying to
>> avoid. Ie- I get to the end and go 'ooh.. only this
>> number of cells were filled in'. More comments in
>> the P/R about what I want to achieve and fall-back
>> positions.
>>
>> >
>> > There's also a battery one where the info for
>> the cells have different
>> > timings (because one has other info), so I want
>> to be able to clear a
>> > range of cells rather than just reset and start
>> filling the info again.
>>
>> That may be a bad idea, maybe better to implement
>> some synchronization /
>> drop readings out of sync.
>>
>> Reaching a consistent state, the BMS will
>> calculate deviations etc..
>> Crucial on that part is an analysis of the
>> consistency of the cell
>> readings to determine the reliability of
>> deviations exceeding thresholds.
>>
>> See my comments in BmsSetCellVoltage() and list
>> thread:
>> http://lists.openvehicles.com/pipermail/ovmsdev/2021-February/015079.html
>>
>> I've skimmed the comments but will read properly and
>> digest. Yeah it might be best if I just clear the
>> values at the start of the more often running one and
>> then once the other ones come in it will finalise
>> once it gets to the end of those.. so they aren't too
>> far apart.
>>
>>
>> >
>> > I've modified slightly the dump for the battery
>> cell
>> > voltage/temperature, allowing for either or
>> both columns to be visible
>> > if available. It also copes with the above 'not
>> set' scenario.
>>
>> Sounds good.
>>
>> I'll push this once the FinaliseCellVoltage
>> pull-request is finalised and accepted.
>>
>>
>> >
>> > Finally, the controversial one: I am using
>> std::vector<uint8_t> as a
>> > buffer in my ioniq5 code.. and I wanted to be
>> able to use it for the
>> > polling instead of std::string. I've not
>> replaced the std::string but
>> > added the ability to have either.
>> >
>> > If my aversion to using std::string for binary
>> data is misplaced, then
>> > I'm ok with the currently small modification to
>> my code that would use
>> > the std::string version.
>>
>> The general use case of ISO-TP data is actually
>> dynamic binary strings.
>> They are meant to and need to be easily
>> aggregated, cut, merged,
>> partially extracted etc., so they really are
>> strings, not vectors (type
>> wise).
>>
>> Hmm.. I'm not sure I entirely agree about needing to
>> aggregate/cut/merge; we know the size of the buffer
>> after the first packet comes in so we can pre-set the
>> buffer internal size and append data as it comes in
>> without casting from uint8_t* to char *. Even if the
>> size is wrong, we can still very easily append to a
>> vector.
>>
>> ON the extraction, I have efficient templated
>> functions that extract the data from the
>> std::vector<uint8_t> buffer.. including to a
>> std::string if required, or to
>> big-endian/little-endian signed/unsigned integers of
>> 1..4 bytes with sign-extension now. These also check
>> bounds so are quite safe - possibly safer than the
>> macros. The bounds check has already proved itself
>> useful.
>>
>> I have pushed up a draft request 'single poll to
>> buffer' as it is the easiest way to describe what I
>> want to do. The first commit is the meat of the
>> change ... but the second is adding all the utility
>> functions. They probably don't belong in
>> vehicle.h/cpp, but that's easy enough to change. I
>> had them in my ioniq 5 specific code - but have
>> shoved them in there just for a point of discussion.
>>
>> The great thing about the template functions here is
>> that they should expand inline at compile time to
>> quite efficient code.
>>
>>
>> Regards,
>> Michael
>>
>> //.ichael
>>
>>
>> _______________________________________________
>> OvmsDev mailing list
>> OvmsDev at lists.openvehicles.com
>> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>
> --
> Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
> Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
>
> _______________________________________________
> OvmsDev mailing list
> OvmsDev at lists.openvehicles.com
> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
>
>
> _______________________________________________
> OvmsDev mailing list
> OvmsDev at lists.openvehicles.com
> http://lists.openvehicles.com/mailman/listinfo/ovmsdev
--
Michael Balzer * Helkenberger Weg 9 * D-58256 Ennepetal
Fon 02333 / 833 5735 * Handy 0176 / 206 989 26
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openvehicles.com/pipermail/ovmsdev/attachments/20221029/77faae21/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 203 bytes
Desc: OpenPGP digital signature
URL: <http://lists.openvehicles.com/pipermail/ovmsdev/attachments/20221029/77faae21/attachment-0001.sig>
More information about the OvmsDev
mailing list