Build and test of the first bluetooth supported module, plus the beginnings of a mobile phone app.

I made the mistake of not taking a photo for the blog before installing it on the car, but the first bluetooth version is now built and on test. This time it's sitting on the right hand side of the car, so now I have no OEM modules installed at all (my car is a UK 5.2 model so it only has two rather than three Cat ECU's). So far I've driven it maybe 50 miles or so. There isn't a lot to report because the software is basically the same as the first prototype, although some minor mods have been made.

As with the first version I've potted this one into a box, although this time it's a 3d printed box produced to the same dimensions as the original. This means it fits on the original mountings properly but the size made fitting the extra bluetooth hardware a bit of a squeeze. On the 355 there's room for a taller box which would help, but it would be interesting to know whether that is the same for other models.

One thing I found was that the circuit I built for the bluetooth module can't have the firmware upgraded. I was aware of this deficiency during bench testing but in my haste to put it together to test on the car I forgot to deal with it. It's a really easy fix but I'll have to build another module to do so. I keep saying I won't pot them for testing but the fact is that the right hand one in particular is very exposed and without protection from moisture it'll be killed in no time so I have to take the risk of potting them.

Here's a picture from an odd angle (camera pointing up from underneath the car) of the bluetooth version installed on the car. The rear wheel is somewhere off to the rigght hand side. I will try and take a better one if I take it off the car again later!  I did something slightly different with the cables this time and the board is installed flat rather than on its edge. There isn't much room in there for the bits I need.

And here's the other of the two 3d printed boxes matching the original. I could swear I ordered black but they turned up white. Never mind. The one on the car is sprayed in black paint to cover up the mistake (a bit - you can still see the white edges!).

On the mobile phone app front, I have two solutions, both of which use bluetooth:

  • A simple terminal based application. This shows the same output as the video I showed in the update on 12th August. The only difference is the connection between the terminal and the module is bluetooth instead of a USB cable (the USB cable is still an option on the bluetooth enabled version though).

  • A specific application that you can run up on the phone that shows key information. This uses a different interface and the software's output has been altered to make it possible to format the values in a sensible way on screen.

The latter option is in the early stages at the moment but I am able to show temperature and output voltage on the phone updating in real-time. It just doesn't look very pretty yet. The former option is better for logging because most terminal applications can capture output as standard. I will add a video to demonstrate these in the next update.