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Holy poo poo man, this is amazing. I'm hoping to Tesla swap some stuff in the coming years and this is a real motivator to see come together like this. A few points - on that oil cooler fan from the Dell server, is that exposed to the weather? I doubt it will last very long, if so. Also, on CAN messages, I am guessing you already know this, but if you get clever with C structs and unions you can make a data structure that allows you to shove arbitrary data formats (well, up to a total of 8 bytes, since that's the limit of a CAN message) in without regard and then pull them back out as bytes and feed them into the CAN message mailboxes easily. It's very useful when trying to get, say, 16 and 32 bit integers, or floating point numbers, or a combination of data types across a CAN bus without ripping your hair out. e: oh and I'm curious why the input shaft has to be stopped while driving? Is it because in full electric output mode the trans was designed with the assumption that the engine would be stopped in mind, and it works against the input shaft with one of the planetary gearsets or something? I'm not super familiar with the internals of that trans.
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Jun 17, 2020 06:38
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drat, that's some great work, especially the displays. I've been dreading that kind of thing. A few things though - one, if you wanted to get the factory speedo working, you could use a chip known as a DDS chip. Stands for Direct Digital Synthesis. Basically you give it a crystal reference and hang a line driver or op amp on the output and shove commands at it with SPI or i2c depending on which one you buy. Analog devices makes a lot of nice ones that will do crazy wide frequency ranges. You tell them the frequency, phase (only really matters for applications other than this of course, like if you were building a radio LO section or modulator) and possibly amplitude and it just spits out a sine wave for you. Another, for the fuel gauge. I'm actually working on a project for my Honcho LS swap to deal with that. With a correctly chosen set of resistors and a handful of n channel mosfets (or possibly cheap optocouplers, to allow for positive or negative reference rather than assuming ground reference) I can output resistance anywhere from 0 to 90 ohms with like a hundred points in between. It's not even that hard, the key is when you realize that an R-2R network (or a parallel resistance ladder, depending on the curve of the sender you're trying to emulate) doesn't actually have to be all the same values and the curve produced doesn't actually have to match the curve of the sender if you don't mind adding a lookup table in your firmware, all that matters is that the points are close enough together across the whole range that you can set the needle anywhere you want instead of it visibly jumping from step to step.
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Jul 4, 2020 22:14
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Well poo poo, I should have expected you'd already considered that all  well done.
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Jul 4, 2020 23:17
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Oh drat that's a cool chip. I usually stick with Phillips NXP for io expanders but I'll add it to my library. The reason is likely power dissipation like you thought. I plan on using like 1 amp mosfets and half watt resistors along with a 750mA polyfuse in series with the whole thing so that it's idiot proof, because I know the idiot who will be installing it. The only reason I'm doing it is because I like overcomplicating things, digidashes for FSJs START at 584 dollars, and I have this weird thing about wanting it to look 100% factory unless you open the hood but also don't want to hack in extra sensors, so I'm pulling the engine data from the class 2 serial data bus on the ECU just like the GM dash would, and using it to drive the factory gauges.
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Jul 5, 2020 02:50
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That's for drat sure, I'll check those out. Ask me about the time I missed a line in a datasheet and put SOT23-5 footprints on a board and then the parts showed up and they were SC70-5 instead, though. That was fun, since I needed it working tomorrow. GM Class 2 is lame and almost all the transceiver chips for it are either on the tail end of NRND or completely discontinued, which is making me cross. I don't want to have to decode that mess manually or use makerspace grade junk, I want it to be perfect and look like an OEM built it. How is the Volt heater? I was talking to Elviscat a couple months ago while looking at his Leaf and it seems like they went from the barely adequate resistive heater to a bidirectional heatpump setup, so I am really hoping to use one of those (or whatever is like it and best bang/buck/complexity wise when I get to do one of these projects) for my next build.
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Jul 5, 2020 19:54
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The pipe work is really not as bad as people think - all the aluminum tubing is standard diameters. You could pretty easily put a system together using compression fittings or regular 45 degree flares if you don't feel like TIG welding the fittings, and could use soft copper instead of aluminum for anything you have to buy. The hardest part would be routing the lines and figuring out how much refrigerant and oil to use, honestly. I used to be terrified of it but having learned how to refill AC systems and doing a fixed HVAC system install from the install manual has taken a lot of the mystery out of it.
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Jul 6, 2020 17:54
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Well that's rather annoying. I had no idea the fitting issue existed, I'm used to models where I walk into the breakers and there are five or ten in a row so I take the parts I need with the lines still on them and they don't bother charging me for the lines at all.
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Jul 6, 2020 23:20
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Sounds like you need to find someone over here willing to go junkyarding for you and send you gifts for every major holiday.
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Jul 7, 2020 08:50
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That's a really cool current sensor, I'll have to add it to my list. I usually use Allegro current sensors since my wife used to work there so I could get 5 minute answers on what the best thing in the lineup was for my project, but I don't think they go over 150 or maybe 200 amps. BTW, I think I forgot to mention but yes that's what I meant about structs and unions a page ago - every time I've created a custom canbus setup I've made a header file that all my code #includes that contains a struct/union definition for every message I use, which allows me to rebuild all my MCU firmware images off one unified set of message definitions without worrying that I forgot to update something. I'm curious why you put your io expanders on i2c instead of SPI - avoiding overloading the spi bus since you already have a ton of bandwidth requirements from the displays? Looks like I'm likely going to end up with mcp23s18 instead of the mcp23017 you recommended because I'll be driving opto LEDs (thus open drain preferred) and hate i2c* and have plenty of space left on my spi bus. * Long story from 2006. I2c bus can get hosed, it's a personal hate-hate relationship following months of hell from a lovely i2c bus that ruined my summer
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Jul 9, 2020 07:52
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| # ¿ May 22, 2024 13:10 |
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I've never had timing issues on i2c with trace routing but I had every other issue. Designer screwed the pooch choosing addressing and everything conflicted with everything with not enough address pins on any chip to make it stop? Check. Multiple voltage domains? Check. Buggy prerelease chips (early stepping of the Intel 82575EB) on the bus with no way to disconnect them that conflicted with everything for no reason? Oh yeah. A billion bus switching chips to separate sections of the net but never where you needed them? Uh huh. He even crossed clock and data in one place but luckily that was easily fixed. It was a mess. It scarred me for life, I swear. The 23s18 looks like it's the 23018 but with SPI instead of i2c. I hadn't seen that analog setup either actually. Kinda a cool idea.
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Jul 9, 2020 08:47
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