Difference between revisions of "Porsche 928 LH Replacement Prototype"
From Francois Louw
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The discussion forum can be found at [http://forums.rennlist.com/rennforums/928-forum/602152-plug-in-lh-replacement.html Rennlist] | The discussion forum can be found at [http://forums.rennlist.com/rennforums/928-forum/602152-plug-in-lh-replacement.html Rennlist] | ||
| − | I will | + | ===Hardware Selection=== |
| + | Step 1: Requirements | ||
| + | |||
| + | 1) I need to know what each pin of the ECU connector does. In the end when everything is done I want to plug my module in and do nothing to the rest of the car and it should work. | ||
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| + | 2) USB/Serial port on the board that will allow remapping while driving/dyno | ||
| + | |||
| + | 3) Possibly I would want to replicate the bosh diagnostics k/l lines, but I think that would be redundant given that the serial/usb will be able to give errors and diagnose. | ||
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| + | 4) The processor that I must use must preferably have a/d convertor, lots of digital I/O, support serial and USB, must also run fast enough so that I wont have trouble when it comes to coding. | ||
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| + | 5) Must withstand the "harsh" temperatures and EM interference that is present in a car | ||
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| + | 6) Must have lots of LEDs to impress everyone that looks at it | ||
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| + | Step 2: Component Selection | ||
| + | |||
| + | Ok here is my list of components, I know that you can get better and the whole ARM vs. MIPS instruction sets blah blah blah... | ||
| + | |||
| + | But the components are chosen, not much gonna happen to change it. | ||
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| + | CPU: Microchip PIC32MX575F512L 100pin TQFP | ||
| + | EEPROM: 256K Dont care what brand, going to use the Atmel footprint <= The EEPROM is optional, if the internal flash of the processor is not enough | ||
| + | Switching FET: ST Micro ST-D17NF03L <= They are monsters and completely overkill but also cheap and will get the job done | ||
| + | BJT to switch FET: BC848 <= Switch sitting inbetween 3.3V CPU and 12V FET | ||
| + | Comparators: LM239, Any brand <= Used to switch from 12V digital inputs to 3.3V for the CPU | ||
| + | Op-Amp: LM324, Any Brand <= Need to translate the MAF Voltage to 3.3 and the engine temp sensor, etc etc | ||
| + | Power Filters: BNX012, 1N4004 protection diodes, Input voltage limiting Diodes <= EMI is bad inside car, thus need to filter | ||
| + | Voltage Regulators: LM317 <= Need 8-10V intermediate voltage, ST493C33 <= Current limiting 3.3V supply for CPU | ||
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| + | These components are the major components and I did not list all the masses of resistors, caps and diodes used in the circuit. | ||
| + | |||
| + | ===Schematics=== | ||
| + | Here are low resolution pic of my schematics, I made it low res on purpose, I don't want other people stealing my design and making money out of it. | ||
| + | |||
| + | First Image is page 1-4 of the schematics, second image is page 5-8. | ||
| + | |||
| + | Page 1: CPU | ||
| + | Page 2: EEPROM | ||
| + | Page 3: Power | ||
| + | Page 4: Outputs | ||
| + | Page 5: Digital Inputs | ||
| + | Page 6: Analogue Inputs | ||
| + | Page 7: LEDs, USB and Serial | ||
| + | Page 8: Connector | ||
| + | |||
| + | The third image is the PCB layout, blue is bottom layer, red is top. This board is made using only 2 layers. Most probably if I make second version I will have to go 4 layers to make enough space to route for different connectors. | ||
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| + | Next step is making the actual PCB, populating and soldering | ||
