The IO-Extender
The IO-Extender
Bear with me if this entry feels a bit like a great big advertisement for this thing. It’s pretty new, so not many people have even heard of it, and I simply think it’s the greatest add-on device for the MegaSquirt out there right now.
What is it? It’s a unit that connects to the MegaSquirt 2 and 3 CPU’s via CAN (Controller area network), so it essentially networks with the MegaSquirt unit. It has a CPU that has oodles of IO pins, so it takes the MS2 CPU that barely has any spare IO pins, and gives it TONS more. Where in the past, you pretty much had to pick and choose which features you wanted, ESPECIALLY if you wanted things like sequential injection, COP, and stepper IAC all at the same time because all of those features hog a lot of the “spare” CPU pins.
Monday, February 22, 2010
This is what you get in the package. The IO Extender mainboard with the SMD components already installed, a DB37 connector and it’s shell, and a handful of components that will get you started building several of the primary input and output circuits. The case was extra, but I didn’t want to try to source it myself, so I went ahead and got it.
Sadly, the case did not come with the endplates cut. With a bit of improvising, I managed to do it myself, and it turned out all but perfect. Little trick I learned the hard way.. When using a grinder/cutoff wheel to make those slices, do them on the inside, so that you can’t see the over-run on the ends from the outside of the unit.
The wire on the left is a pull-up resistor on one of the VR inputs. This should allow me to bring the van’s VSS (speed sensor) into this unit. I’ll be able to display the vehicle’s speed as well as realtime gas mileage numbers with this.This might allow me to get even better gas mileage than I have been able to get so far.
And the two diodes and a bit of wire in the picture on the right is my “active low” input circuit.. Mostly just a proof of concept for future uses, I’ll probably set it up for launch control for the time being with a toggle switch. Why I need launch control in a work van, I dunno.. But I’m sure it’ll provide some shock and awe to the general public. :)
That’s it for now.. This device is very new, and I imagine I’ll be blazing some trails with it, the documentation is sparse at the moment, I’ll probably be able to write it by the time I’m done. ;) Future plans for this..
Monitor/log: Fuel pressure, oil pressure, fuel temp, oil temp, intercooler charge temps both going in and coming out (and displaying the difference in a gauge on the laptop screen), ambient air temperature, vehicle speed, EGT - exhaust temp, realtime barometric pressure. I also plan to have it control my air conditioning, when I finally get around to plumbing it back in. I’ll have it control the AC compressor so that it can disengage it over a certain RPM, or over a certain throttle amount (WOT), and I can even put a thermocouple into the evaporator and let it cycle the compressor based on the temperature of the evaporator.. A little overkill, but why not, I’ve got the computer power there to do it.. It may also be possible to feed the MS2 CPU information about the AC being kicked on, so that it’ll preemptively open the idle valve a bit just in time for the compressor’s big hit, if the engine is idling.
I plan to add a little bit at a time, here and there as I get the necessary sensors. I’ll keep the blog updated as I go with how it’s working out.. Here’s a gauge cluster that I’m in the process of making:
That’s pretty much the dash I’m running right now, with the exception of a few things moved around and the speed added to the display. In the end, I may start from scratch to get everything where I want it to be and keep it all looking good. It’ll definitely keep evolving as I add more sensors.
