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Open source product development for OBAM aircraft

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Apr 15, 2012 6:52 am Post subject: Open source product development for OBAM aircraft

At 07:54 AM 4/15/2012, you wrote:

 	  Quote: 	
		    The days of writing machine code are over except for the simplest 

 tasks that somehow need specialized hand tweaking.


	




   Agreed. A little 8-pin PIC watching a bus

   voltage to flash a light . . . or a timer to wig-wag

   the landing lights is just such a 'simple' task that

   yields nicely to programming in assembler.



   But as soon as you need to do any math beyond a

   simple integer add/subtract the glow is off the

   assembler rose.



   If I were teaching a hands-on class in uC product

   development, we'd certainly use assembler to explore

   the various registers. But evolution into higher

   order functionality is not well served by learning

   to the assembler necessary to do floating point math

   or deeply nested prioritizing of tasks.



   Not exploiting advantages of higher order language

   compilers is like running a roofing company without

   nailguns.  If your roofers or programmers are getting

   a good wage and have a deadline to meet, efficient use

   of manpower and time is the name of the game.

   Bob . . .

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gregmchugh

Joined: 03 Apr 2012
Posts: 42

Posted: Sun Apr 15, 2012 3:17 pm Post subject: Re: Open source product development for OBAM aircraft

Bob and all,



I had a little more time to play with the PICkit 1 Flash Starter Kit since my

last update on the project.



In our last episode, I had loaded the Hex file that come with Lesson 1

onto the board and it seemed to function fine (you push a button and an

LED changes state).



Next, I checked that I could reassemble and load from the code

that came with Lesson 1 (switch debouncing). Worked fine with the latest

MPLAB IDE that I downloaded from Microchip. Hex file seems to function

the same but it is different than the hex file that come with the kit. Not

unusual for this to happen (assembled years later with a newer version

of the toolchain). Something I may take some time to look at but

since I am planning to use the C version not something critical to do.



I next compiled the C code that came with the lesson and it had one

error (due to a missing define to allow the use of legacy header files)

and two warnings (the count for the timer was defined as 20. instead

of 20, not sure why, giving a warning about float to integer conversion). A

Google search solved the first one and the second one was readily found

by looking at the warning message. The legacy header define is

needed to allow older code to be compiled under the current 

toolchain. I would guess that no one got the job of updated the C

code that comes with the Starter Kit to reflect changes in the standard

header files.



Downloaded the hex file produced that had been produced from

the C code and it seems to function as expected. All in all, about

what I would be expecting at this point. Getting to this point would be

pretty easy for anyone familiar with embedded software development but

a novice might have gotten stuck along the way. The MPLAB IDE is

feature filled which is good for experienced users but can be daunting

for a novice. Next I will do any porting required to move over from the

PIC12F675 to the PIC12F683. Time to take a look at the datasheets for

the chips and find any significant differences.



I have only the MPLAB simulator to investigate how the code executes

and I will next spend some time learning how that works. Seems pretty

straightforward but I have only stepped through the code. Need to

see how to set up the external stimulus inputs into the simulator.

Again seems to me like something that is pretty familiar but I am not

sure how a novice would look at it.



I decided to go ahead and order the low-end debugger (PICkit 3 Debug

Express plus an interface adapter and the PIC12F683 ICD Header) from

Microchip. That should be coming tomorrow and I will have access to

debugging in the chip. So, for those keeping score the Flash Starter Kit

is $36, the Debug Express is $70, the interface adapter is $10, and the

ICD header for a specific chip is $25. I would call this reasonable cost

to get what you get but a novice might say it was too much to get started.



You could get by with just the Starter Kit but I like having a view into

the chip as the code is running. You could skip the Flash Starter

Kit and go with the just the Debug Express but the Starter Kit does

have all of the hardware to support the tutorials and some

prototyping area to play around with. The PICAXE and Arduino folks

get around the debug issue by keeping the serial interface open to the

development PC, allowing debug messages to be displayed. Works

fine for most simple applications but it would tie up two pins on

our 8 pin device.



That is enough for now, I am still planning to write up a short summary

of all of this for anyone who wants to give it a try. Only a few small

gotcha's up to this point...



Greg McHugh

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 17, 2012 9:18 am Post subject: Open source product development for OBAM aircraft

The ECB layout is done. I'll put it down for a few

hours and then 'proof' it against the schematic.



I'll publish the ECB layout and schematic as soon

as I've confirmed their agreement.

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 17, 2012 9:03 pm Post subject: Open source product development for OBAM aircraft

At 10:03 PM 4/17/2012, you wrote:

 	  Quote: 	
		  

<retasker(at)optonline.net>



I don't know what you use for board layout, but if you use something 

like Eagle from http://www.cadsoftusa.com/ the layout connections 

will always agree with the schematic since they are linked.


	


  I use ExpressPCB which does have a schematic capture

  feature. Never did like the looks of their schematics.

  I grew up with ARRL publications. the look, feel and

  smell of their publications symbols became part of my

  DNA.



  Also cut my teeth on ECB layouts with little reels of

  black, red and blue tape and donuts. All the time

  I was putting parts on the board, I was working out

  the mechanics of heat sinking, current density,

  vibration resistance, ergonomics of the wiring,

  etc.



  Auto-routers don't mesh well with that train of thought.



  So I still enjoy doing the layout "by mouse" with

  design goals aforethought. Going thought the schematic

  one trace and component at a time is when I cull

  the schematic for bugs. At HBC, we had guys to do

  layouts for us but they didn't know much, if anything,

  about the mechanics of the end-product. But it did made sense

  for big, complex boards. I'm more comfortable somewhere

  between tape-n-dots and full up schematic capture

  with autorouting.



   Bob . . .

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