Today I’ve been building two more CanSee dongles. As the case is slightly different than the one of my development build, the screws don’t fit, so I needed to tape the cases, but the dongles do work, despite of the tape 😉
These two babies are definitely test builds, meaning that I experimented a lot on how to put the different elements together, putting them in the wrong order, placed them upside-down and all that kind of stuff that occurs while experimenting.
But they are operational 😉
Anyone interested in getting one?
Just be warned: I’m not a professional and doing this just for fun, so the risk is fully yours! Although I’ve tested them in my car (which did not blew up … uff) I give no warranty and will not be responsible of whatever you do with the dongle.
The next release of CanZE for Android will be released in the next few hours. I won’t be bothering you with with the usual bug fixes and small improvements, major internal cleanup, nor with the polished up support for the CanSee Dongle, about which we’ve teased you already so much. Though it is worth mentioning that using that dongle made a few things go so fast we had to tweak a few things to avoid the proverbial drinking from a hose. A few things are notable though.
Our friends in the UK will hopefully find our miles support vastly improved, especially in the consumption and driving screen.
After years of head scratching and lacking the means to find the issue, we can now finally get to the BCB and pry out all of it’s DTCs. As the BCB contains charging failure information, we’re really happy with this result. The issue was, as usual, completely trivial and implemented in maybe an hour so, but that’s always in hindsight.
We already announced TPMS. If you have a TPMS enabled car, get the IDs now before you have the tyres changed and then immediately again. The writing function is slightly under-tested with ELM dongles, so tread carefully. Feedback appreciated.
More is in the pipeline, which I think you will like.
While looking for some stretched screen, I came up with one of these new dash camera devices (1280×400 pixels). OK, the camera in itself doesn’t really interest me, because I only want to use it to make CanZE run on it, which is actually quite easy to do.
The only thing on that device that I do not like at all, is that the USB connector seams to be used only for power, so I can’t use it as development device out of the box but need to compile and transfer the app package in order to be able to install and run CanZE. 🙁
But at least the PlayStore is available out of the box and all underlying Android settings can be reached easily …
Micro introduction: A CANbus, which is used to connect all computers in the car, can only carry chunks of 8 bytes plus an ID, called frames. All data used to actually operate the car, such as switch positions, speed, and hundreds of other parameters are stuffed into unique frames and send out freely, almost always at fixed timed intervals. This is why we call them free frames. There is zero standardization among car makers on the meaning of the ID and the bits inside. Commercial dongles are not really designed to pick these up and have a lot of trouble doing so reliably or at all. (hint: “Timeout on ATMA” anyone?)
To actually diagnose the car, far larger “messages” are required. Even a VIN doesn’t fit in one frame, let alone i.e. the data for the voltage heatmap. For this purpose there is a protocol called ISO-TP which allows you to send longer messages. A software layer chops it up in frames, adds some synchronization data and sends it on. Exactly the same happens for long answers. ISO-TP formatted messages are almost exclusively of the query-response type. One participant (say the dongle or the dealers diagnostics tool) requests something, a computer on the bus answers. Even entire firmware up- and downloads are performed this way.
Why is this relevant? The ELM327 based dongles have basic support for ISO-TP. It’s a pain to set up, but it works and it’s actually what they are designed to do. The caveat being it only works for receiving long messages. We never gave this a lot of thought as the queries we put to the car always fit one single frame. Until the TPMS requirement came up. Writing the valve ID’s requires sending a long message. We implemented “long message ISO-TP” from the get go in the CanSee DIY dongle, so after tedious debugging, we knew setting TPMS worked, but now we had to tweak the driver for the ELM327 dongles to support long messages.
Luckily we were not the first. This nut was already cracked by Cedric Paille, the hero who made DDT4All. By carefully going through the logs of DDT4All, we could modify our ELM327 driver to now also send long messages.Thank you Cedric! The crazy thing is that if you use a commercial dongle, it does quite a bit of the ISO-TP hard work for receiving frames, but for sending quite a bit more is done CanZE and suddenly it is timing-relevant. This is what actually held up a new CanZE release.
Teaser: we have more things up our sleeves regarding not just the CanSee DIY dongle but also for the good old ELM’s. But first: a few final test and then release. As always, stay tuned.
In the next release, which we will try to push out really soon, the Tyres screen has been augmented with a section where you can read the IDs of your TPMS valves and write them back. So, if you have a second set of wheels with TPMS valves, simply make sure you know and remember the IDs of the valves, and can write them back in after a change.
At this moment we have no way to let the car reliable learn new valves with unknown IDs, so you need to visit the dealer once more to get to the IDs of your other set of valves, but from then on, you’re done. Also, if you happen to buy after market valves, check the packaging if there is a 6 hex digit ID printed. Might save you a dealer visit.
If you have TPMS, our advice is to read out the IDs as soon as the next release is out and store a screenshot somewhere.
Thanks bjaolsen for the information and Richard for letting me try this on your car.
While heavily a Work in Progress, Bob has started to put together some decent documentation on the dongle. It’s in the Wiki section of the firmware on gitlab. Have a peek and maybe you want to go on an order spree.
On the hardware side, as you probably have noticed we’ve progressed from the breadboard to veroboard-and-hot-glued in an OBD2 dongle enclosure. At least our builds are now a bit wife-friendly 😉
On the software side we’re working on a few features such as direct access to the Multimedia CANbus that Bob mentioned in the previous post, It will open up a few possibilities you will really like (more on that later). Also, we’re working on making the thing a bit more secure, but also more friendly for the non-technical user.
And then there is the ton of other things small and large. To name just a few: – some things need to be slightly changed in CanZE now that is fed with data so much faster – a setting screen in CanZE for this device – low level technical stuff to make more things possible
For the techies: implementing sending multi-frame ISO-TP messages is needed. It required a lot of testing and coding and what not. This is how my desk looks around midnight. CANbus sniffer (Arduino DUE with GVRET) under USB control, T-cable with custom RJ-45 pinout, RJ45 splitter, RJ45 coupler with a CAN termination resistor tucked inside, RJ45 power insert contraption with lots of hot glue, the DIY Dongle being monitored over USB ……..
Is anyone experienced in moving this sort of home grown garage build stuff to the level of a decent and efficient PCB design without using a development board, a production run and maybe even fulfillment?