jharvey wrote:Fred wrote:nitrousnrg wrote:I'll keep the capacitors on the outputs as long as they don't add significant lags.
Why? You're just coupling your CPU references to the external connection on the other side of those caps, ie, you're generating noice that you don't need to. Ditch them on outputs IMO.
It's kind if interesting that your concerned with the noise generated by digital signals routed through a 10 ohm driven 100nF cap. If it's a concern, they don't have to be populated.
Thats why I didn't argue a lot about the capacitors... I don't think I would populate them in my first prototype.
That switch on blip (damn, it took me a while to figure what it means :P), would happen only on the startup... if we keep the microcontroller constantly powered on the blip won't happen every time (btw, is the blip mentioned in the datasheet?)
I'm thinking about how often I have to reconfigure the radio clock, that would be the same frequency of pin blips, or am I wrong?
You could be right about that, yes. Radio clock, perhaps, yes. It's more about what happens if there is a cylinder with a good AFR mix in it when that happens, BANG, and at what crank angle? :-/
The 74hc parts would be of some time of enable/disable design such as the tri state buffer chips. The idea being that we can force control of all pins with a single other output pin that is known to behave predictably. The other part of the equation is that the pin state at default not running MUST be the same as when reset is held down or when the serial monitor is running, ie, during firmware load. If something gets inverted across these states then it spells fire/burned coils/injectors.
I think this could be solved, someway.
For example, I see 3 situations where this can happen:
* When you connect the EMS to the battery.
* When there is a reset, or debug, or anything invoked from the PC through the serial communications.
* When you flash the microcontroller
Correct me if I am wrong, but I'm putting a constant 12v supply to the micro, and everything else is powered from a switchable supply. I mean, the mosfets drains will only see 12v if the switchable supply is switched on. I suppose that those switched 12v are present when the key is in the ON position.
So,
* When you connect the EMS to the battery:
You shouldn't have the key in "ON"!!
* When there is a reset, or debug, or anything invoked from the PC through the serial communications:
We could sense those 12v. If they are present, then it is not safe to perform a bootload/debug/reset. Ask the user to turn off the key.
* When you flash the microcontroller:
The bootloader flash should happen once, and again, there is no reason the have the ignition key in ON. (I'm not sure about the key naming in english, lock,park,on(?),start...).
I don't know what could I do to dodge this when the reset is hold down (btw, I don't have a reset button, put that in the compliance doc if you want one)
Hey, that is important!
There are some hardware recommendations that could be put there, like the schottkys for the AN pins, or automotive regulators (LM29xx). But... in order to help on the pin out decisions, I need to take a closer look to the datasheet.
I may be able to be convinced, but right now if you asked me, I'd say no. I see quite a lot of value in having a standard set of pins that need to be connected to a standard set of sensors. I see a configurable IO to variable system for the core items as another way for noobs to be idiots and screw stuff up. I realise that we'll need code like that for the spare pins sooner or later, but even then, I don't know if allowing CHT to be on adc1.0 or adc0.1 by configuration is a good idea. You could convince me, though. Esp if we hide it in some advanced tab or something and it doesn't interfere with speed of running etc.
And, there is no need to change a single input pin. A more reasonable way would be to select which version of hardware you are using, so you are automagically changing all the pinout, in a single click. The hardware developer is in charge of distribute the correct pinout. Anyway, I wasn't thinking in the users, but in the guys who could make their own hardware. Really, its quite hard to route a random set of pins, at least when you intend to have a big, nice analog ground plane.
Btw, I almost ask "The" professor about the mosfet gate isolation, but the guy went home earlier today ¬¬