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Learning CAN BUS Communication for OBD2 (and building the communication device)

I always wanted to know how CAN bus worked. I've heard about it in the context of automotive communication back to the early 2000s, when my friend who worked at Halfords, used to regale tails of accidents involving screws and CAN bus wiring, leading to all kinds of unrelated systems suddenly changing their behaviour. I had absolutely no idea how it worked, but understood that it was some kind of network allowing data to be fed around the car using fewer wires than a conventional toggle switch and relay type system. Fast forward many years when I first ECU swapped my first Chimaera for the GEMS control unit, I was introduced to the concept of OBD2 and PIDs (Parameter IDs). I understood that the data was brought in using packets at a reasonably high refresh rate, and that the network was bi-directional; if an error code was sent to my OBD reader, I could send back messages to clear the error. Cool! Moving to my current Chimaera project, I knew that I wanted to use the PIDs output by
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CNC Manufacturing

  I really like this part, but it is at the same time really rather stressful. The end result can look beautiful if executed correctly, but mistakes are severely punished. Any flaws in the design are placed on display for all to see, likely rendering the part scrap or resulting in something that will not function as intended. For this reason I have been very thankful for the rather cheaper and quicker additive rather than detractive machining process of 3D printing. Across the interior design, I currently have a number of machined pieces which comprise the switch plates to sit either side of the radio, and the instrument pod. I am considering some rather challenging air vents to add to these but for now I want to get the electric related parts completed so that I can continue with the car wiring harness. Deciding to start with the simpler and less expensive assembly first, I began by having all of the components printed in white PLA. The surface finish isn't brilliant, but with a l

Testing and Refining the Code

Following delivery of the new back-lit decals, a rather significant delivery arrived from PCB Cart with the Version 2 rear PCBs and additional two testing sets of remaining boards, giving me now 3 full sets of test boards and cables to play with. My focus therefore turned to testing the new rear PCB, which had a number of alterations to correct input routing and signal conditioning errors present in V1, preventing me from testing several features.  Along with the new boards, I has also designed a relatively simple testing board, bringing all of the simulated control signals from a messy breadboard full of jumper cables and loose earths to a proper board with nice clean signals. In my rush to design it I had made a couple of silly errors in the design that required a little bit of re-wiring of the underside but after a some time, I managed to successfully test all outputs as working correctly. The next phase was to test each function one by one, buy opening up my partially developed Ard

Decal Design & Manufacture

I spent a huge amount of time considering how to do this right - it's the bit I'm going to be looking at most when I drive the car, so I want it to look good and do the job it's meant to do, and ideally look like something that TVR could have made themselves. It took many iterations to arrive at a design I was happy with; the main issue being the small analogue dials at the bottom of the decal. The two motor hubs are offset from the centre, so if I were to draw an actual semi circle gauge around them, I would end up with an extended circle which looked very odd indeed. The solution was to angle each dash mark toward the real centrepoint of the circle rather than the motor hub, and to stretch the circle into an ellipse. The exact dimensions of the ellipse took forever to get right, so the dial "looks" like a circle as you feel it should be, but the needle doesn't look wrong travelling on a circular track and thus changing its distance to each mark on the dial.