It's probably not what you think. 
And before I get too far, I have to mention RobG and cubeberg have helped with this. THANKS!!!!
The name is a play on words: "Absolute Pressure" taken from "manifold absolute pressure"; "Cooker" taken from the phrase "cooking the books", or in other words, cheating.
What it is, is one pressure sensor affecting two, 16 bit DAC output channels.
What it will do (hopefully ) is read an (automotive) industry standard MAP (manifold absolute pressure) sensor- in this case an MPX4250A 20-250 kPa (kilo Pascal) / 2.9-36.3 PSI sensor (~100 kPa / 14.7 PSI is ambient pressure at sea level), and appear as up to two potentially different sensors. Possible uses could include: replacing obsolete MAP sensors with more readily available ones because of different output range / scaling; fooling a vehicle's engine control unit to allow for bigger injectors or turbocharging; splitting one MAP signal for two purposes; or affecting pressure controlled devices.
The aforementioned MAP sensor will be connected to whatever vacuum / pressure source. The MCU will sample that and generate an output. But instead of doing a mathematical conversion, there will be look-up tables. This will permit non-linear adjustments to be made, allowing for compensation factors to be applied to the output, tuning.
What I am uploading now, is a Booster Pack version of this, which should be usable with MSP430 and Stellaris/Tiva LaunchPads. Eventually, I want to have a complete stand-alone, with software to interface with it from a PC. I think we are close to that too; but still some details to work out.
Hardware is:
- MPX4250AP absolute pressure sensor- http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250A.pdf
- AD8644A quad op-amp- http://www.analog.com/static/imported-files/data_sheets/AD8614_8644.pdf
- LTC2602IM dual-channel, 16 bit DAC- http://cds.linear.com/docs/en/datasheet/2602fa.pdf
- 25AA512 eeprom- http://ww1.microchip.com/downloads/en/DeviceDoc/22021F.pdf
- supporting resistors, capacitors, do dad's and whatnot's.
Should probably mention I have added jumpers to disconnect V+ from either of the output sensor connections... the board is meant to be connected to the sensors and use their 5V+ to power the op-amp and provide external voltage reference for the ADC, but on my motorcycle one of the sensors has 12v and an internal voltage regulator. Therefore, I put the jumpers in so any sensor with inappropriate V+ could be kept out of the system. I've also put a jumper between the 5v from the sensors and the 3.3v LDO so that the LDO can be disabled if the LaunchPad is operating off USB.
I do not have any presentable code to offer at the moment but am working on it; suggestions will be appreciated... and I'm working in Energia, which might have been evident with my post in the Energia forum: http://forum.43oh.com/topic/4292-multiple-slaves-on-spi/, so be kind.
SingleBP.brd 124.31KB
0 downloads
SingleBP.sch 749.2KB
0 downloads
Comments and suggestions greatly appreciated.
* Please ignore the name "SingleBP". I used that because the 500T version of my motorcycle uses 4 MAP sensors, and the 650T uses two. So "Single" means one unit needed for the 650T.
