Fred wrote:
My final recommendation to go with that is to make sure that it's easy to bridge the three grounds in any combination. Particularly, make sure that you can join the ign and inj grounds to share current capacity as your coil ground path will be under a lot of load and if the connector pins aren't designed for that load it could give you headaches. Make sense?
Your final recommendation is very important, I have two options to address this issue.
1.use a screw connector to joint the ignition and injector low side.
2.use dedicated gnd wire to split current for ignition and low side.
So I extend my diagram as following, which one is better?
this is my 2 pins screw connector
and look at my OEM connector, I think such a single thin pin can not sink ignition current efficiently.
I intend to have FreeEMS control my daily driven car, so I think it is worth to spend more times to address issues earlier.
As for the not-a-stepper idle valve, is it necessary to drive those PWMs independently? Perhaps include an inverter IC such that you can either drive the second FET from the CPU OR from the same channel as the first FET but through an inverter.
When power off, the value stations at middle of the position, So it is possible to drive one side coil of the motor but still need some experiment. As the pin resource is rich for my design, So I decide to use two PWM channels to drive my valve