Intro and Suggested 1st Priority

John Jennings jjenning at
Fri May 6 15:17:22 GMT 1994


I'm a EE/SW Engineer with about 12 years of professional experience.
I currently work for a communications equipment manufacturer.  I've
got extensive experience in design/implementation of real-time
operating systems.  My prior work includes computer-related consulting
in the Nuclear Power industry, and process control for a small
packaging industry OEM.

Steve Baldwin <steveb at> writes:

> Anyway.....decide what it has to do and _then_ decide what can do it.

Ron Rader aka PTM <rlr at> writes:

>   Exactly _what_ are we designing?  What requirements are we trying
> to satisfy?  I'll tell ya one thing, if I'm gonna contribute, it had
> better be cheap.

I can't agree more!!!!!  

I've seen too many projects die or end with a mediocre product due to
fundamental design decisions being made prematurely (even prior to
informal requirements).  This reminds me of the cartoon where a SW
manager gives his subordinates the instructions "You guys get coding
and I'll see what they want!".

Anyway ... let's talk requirements!  Ask yourself the questions
"What's this thing going to do and how can we verify that it's doing
it correctly?".

So far I've seen:
1)	The system would have to work at:
	1.1)	Startup
	1.2)	Idle
	1.3)	Part throttle cruise
	1.4)	WOT
	1.5)	Deceleration
2)	It had better be cheap (< $???)
3)	Ability to talk to the ECM with the engine running.
4)	Inputs:
	4.1)	O2 Sensor
	4.2)	Throttle Position sensor 
	4.3)	Temperature sensor (temp. of what?)
	4.4)	Intake air temp. sensor.
	4.5)	Exhaust temp. sensor.
	4.6)	RPM sensor (maybe an engine position sensor - so you know
		exactly which cylinder needs fuel / spark next (distributor
		mounted of course).
	4.7)	Either a MAP or MAF sensor.
	4.8)	Humidity sensor? - or altimeter?

I suggest that we add:
4)	It had better be reliable (> ??? MTBF)
5)	The ECM must be small (< 4" X 8" X 2" ??)
6)	Standardized RS-232c communications interface.
7)	Outputs:
	7.1)	Fuel Injector drivers.
	7.2)	Alarms?
	7.3)	Timing control?

Food for thought.

John Jennings                      INTERNET: jjenning at
DSC Communications, Corp.          (214) 519-3957
1000 Coit Road, Plano TX 75075

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