Developers geek talk – part 2

Please skip if you are getting tired of this development talk ūüôā ……

While I was debugging the WiFi interface today I was, of course still getting in and out, now and then resetting the dongle, making sure th car was awake, etcetera. And then one of those “aha”-moments struck me.

What if I took a web-server (or even the Wemos reprogrammed) and make it emulate my gateway with possibly prerecorded answers from my car?

Eureka! Not only would I not need to leave my desk anymore, I could do entirely without the car, even tweak values supposedly coming from it. As all the primitives that are available in the real ELM327 driver are also present in the WiFi gateway, it should work. So, I quickly threw together a small “Wemos WiFi Bluetooth gateway emulator” on my ancient Freecom NAS server and verified it could serve at least one IsoTp frame (module temperatures). Like this for the IsoTp primitive:

$PAR = $_GET['f'];
switch ($PAR) {
    case "7bb.79b.6101":
        echo "{\"C\":\"IsoTp\",\"F\":\"$PAR\",\"R\":\"61011381138700000000000000000000000009980D61033A20D000000548000000000000000E721D000001142927100000000000\"}";
    case "7bb.79b.6161":
        echo "{\"C\":\"IsoTp\",\"F\":\"$PAR\",\"R\":\"6161000972C0C8C8C8ACA40000DB8D00002D6DFF\"}";

So here is what that looks like, interface wise

jeroen:~$ curl http://[removed]/wemos/IsoTp?f=7bb.79b.6104

7bb and 79b is the ID pair of the LBC, and 6104 is the command to get the cell temperatures. The real frame contains more data but this is the only part used by CanZE in the heatmap. I have marked those fields in blue. Those are the 12 module temperatures in hex, with an offset of 40 degrees (32 hex is 50 decimal, minus the offset is 10). Then I continued working on the “ELM327Http” device in CanZE, which was sorta done, but was still full of errors. After a few hours of painstaking work, but not leaving my desk (the family was out with the ZOE anyway): success.

As I was 80% done with tedious under the hood changes for the new diagnostics, I had to fix the many problems I had introduced in that area too before CanZE was only slightly willing to operate at all. Did I already mention how that process goes? Well, exactly like that, but now without all of the car back and forth stuff.

Next: sniff the car on all possible frames and put that in the PHP code. After that is done, verify the other screens and then onto the diagnostics. Stay tuned.

Next day edit: of course errors keep popping up and I fix them as we go, but I have now committed the changes to the branch for internal testing. I also too a snapshot of my car (all free frames and all diagnostics of the EBV, LBC and CLIM computers) and put them all in said webserver “car emulator” code.

Posted in Geek talk, Hardware

Leave a Reply