Posted by bill.french on 28 December 2010 - 01:56 AM in General Discussion

Posted by bill.french on 28 December 2010 - 01:52 AM in General Discussion

Posted by bill.french on 09 November 2010 - 06:31 PM in General Discussion

Posted by bill.french on 30 September 2010 - 05:25 PM in Netduino Plus 2 (and Netduino Plus 1)

Posted by bill.french on 26 December 2010 - 10:21 PM in General Discussion

If it's worth anything, after doing everything under the sun i could think of (caps, resistors, chokes, inductors) to quiet the power supply, the aref, the supply to the thermistor, and showed it to gray beard ( ) who teaches microcontroller programming at Rutgers, using an oscilloscope, he was surprised at how quiet i got the power, but we still could not eliminate the fluctuations. Even with just a simple voltage divider -- no thermistor involved. The voltage was solid on the oscilloscope, but the analog readings were wild by as many as 4 bits, occasionally more -- even after averaging 100 readings. Mine was *way* worse using an external power supply -- even a battery.

Posted by bill.french on 09 November 2010 - 01:41 AM in General Discussion

This post covers:

• a very basic circuit using a potentiometer
• a program for reading an analog input port

First, the circuit. You'll want to read about voltage dividers to really understand what is happening. The potentiometer acts as one of the resistors in the voltage divider -- and since a potentiometer's resistance changes by turning it, it provides a good source for the analog input. If you are comfortable with Ohms Law (V=IR) the wikipedia article on voltage dividers is pretty approachable in my opinion. Something important in the circuit is the link from 3.3v to the aref pin. Aref is "analog reference" and sets the ceiling of the analog input. The max is 3.3v. I believe the revision B netduino boards have an internal tie in so that using aref is optional.



... and what it might look like on a breadboard:


... and the program:

using System.Text;
using Microsoft.SPOT;
using System.Threading;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;


namespace NDP_SocketSender1
{
    public class Program
    {
        public static void Main()
        {
       
            AnalogInput a5 = new AnalogInput(Pins.GPIO_PIN_A5);

            while (true)
            {
                string s = a5.Read().ToString();
                Debug.Print(s);
                Thread.Sleep(100);
            }
        }
    }
}

Basically, the program opens up an analog input port (a5 in this case), reads the value into a string, and prints the string to the output window in visual studio every 100ms. As you adjust the potentiometer, the values displayed in debug should change, varying from about 0 to about 1023, which are the bounds of the 10-bit ADC (analog-digital coverter) built in to the netduino.

Since I have a Netduino Plus, I have also set it up send the readings over the network and graph them in a Windows Forms Application, so I could see the results visually as I turned the potentiometer to different positions. It's important to realize that digital inputs read either 1 or 0; analog inputs have a range, and the graph from my netduino plus illustrates this:



If you don't have a netduino plus, you can cut and paste the data from the output window in Visual Studio into Excel or a Google spreadsheet and graph from there.

If this is interesting to you, I would encourage you to search the forums for "analog", "analoginput", and "setrange" for lots more useful information.

Posted by bill.french on 26 January 2011 - 04:36 AM in General Discussion

Posted by bill.french on 23 December 2010 - 02:15 PM in General Discussion

Posted by bill.french on 23 January 2011 - 12:23 AM in General Discussion

Let me start off by saying that I think the netduino and the netmf is wonderful. *BUT* this is something you need to know coming into this, if you've ever done anything with lower level micro controllers. Folks "new to the sport" probably won't run up against this for a while.

There was a bit of discussion on this in an earlier thread:
http://forums.netdui...ch__1#entry6380

... also interesting, in the quadrocopter discussion, I had checked out the timings using my saleae logic and you can see what is apparently the scheduler getting involved:
http://forums.netdui...ndpost__p__7645

I did some new measurements with my saleae so i could zoom in and provide a different perspective of what you're talking about:
using this code: (this was so I could get the timings of the on/offs as equal as possible)

while(true)
{
b = !b;
d0.write(B);
}

I got this:

and using this code: (which is faster)

while(true)
{
d0.write(true);
d0.write(false);
}

I got this:


There is lots of interesting things to think about, I think.
1. It's interesting to me how much slower the first example is
2. We might want to keep track of these types of timings to have a handle on if firmware changes impact the timings at all
3. I wish I could mail Corey my saleae to get the timings under his fluet interopt... which is awesome. (Or, alternatively, I with I was brave enough to try it myself!)
http://www.youtube.com/watch?v=9EcEUbtgO2I
4. I wonder what the impact of things like GC and the scheduler are

#2 sounds like the start of development of a test suite for the netduino, where we can independently test the netduino during firmware upgrades. I might consider taking on this project myself. (Once I learn what a test suite is)

Posted by bill.french on 23 January 2011 - 09:07 PM in General Discussion

Really? Why?

I imagine in real life you have a very strong personality. It comes across in your posts. Instead of hopes and wishes, you have expectations and demands. This has served you very well in life! I'd like to know and understand where in your life this comes from, as I try and find my own path in the world, as I'm sure besides helping you advance through life, it's even helped others around you achieve, if not in admiration of you, than out of fear of disappointing you. I bet you are a good leader. Some people might "get" you, and others might think you come across as a bit of a jerk sometimes, but both will work hard for you.

So, I get ruffled when I think you might be acting like a jerk to Chris and the state of the union here. But this is just me being oversensitive and trying to learn about life and technology. And Chris is his own successful person, with an awesome product, quoted in magazines, etc. and can fend for himself!



I'd like to check out this: http://www.sump.org/...nalyzer/client/
or this: http://www.lxtreme.nl/ols/
using this: http://dangerousprot...-logic-sniffer/ -- which i just noticed is doing exactly what I was doing with decoding IR in this pic:

Posted by bill.french on 23 January 2011 - 03:37 PM in General Discussion

Don't get me wrong, I love the .Net Micro Framework

...but not the Netduino, Secret Labs, or Chris Walker???
Your posts ruffle my feathers! I'm still reeling from the basic comment on loading assemblies.
But, you're obviously brilliant and successful, so, I am still a Fabien Fan. I wish I was at least better looking, but we kind of look like we could be brothers.

PS: Bill, how do you like your Saleae analyzer so far?

I like it, it's very "sexy" in a mac sort of way, and works in 7 and OSX.
..but, if feels very basic, feature wise. I've never used a logic analyzer before, so I'm not sure what I'm expecting. I was trying to "reverse engineer" an IR signal with it, and while it was useful, there was no way to compare two "bit trains" side-by-side from different samples, so I was cutting and pasting screen shots into paint.net. I have no idea if any logic analyzer has that sort of functionality. The software essentially has no menus, so I found myself hungry to do simple things like split the screen in two vertically.

Posted by bill.french on 31 October 2010 - 12:29 AM in Netduino 2 (and Netduino 1)

Posted by bill.french on 07 November 2010 - 05:43 PM in General Discussion

Posted by bill.french on 07 January 2011 - 09:01 PM in General Discussion

Posted by bill.french on 20 January 2011 - 07:00 PM in General Discussion

Posted by bill.french on 06 October 2010 - 12:21 AM in General Discussion

Posted by bill.french on 07 January 2011 - 02:13 PM in General Discussion

Posted by bill.french on 03 January 2011 - 01:27 PM in General Discussion

Posted by bill.french on 27 November 2010 - 02:09 PM in General Discussion

Posted by bill.french on 14 October 2010 - 05:37 PM in General Discussion

Posted by bill.french on 14 October 2010 - 02:08 AM in General Discussion

Well, I've made some progress on my analog input fluctuations.

I borrowed a Rigol DS1052E -- the screen capture is below. I'm still trying to figure the scope out, I've never used a digital one before.

Anyway, is seems only on external power, there's fairly regular pulses of noise on the 3.3V line, regardless if the source is a battery or my 12v regulated supply.

I built the noise reducing circuit in this article, using an inductor and a bunch of caps:

http://www.arduino.c...Lib/Thermistor4

That is the blue line in the picture... so I've at least filtered it out, now, but my readings of the thermistor are certainly slowed.

Any ideas where the pulses are coming from and how to eliminate them, besides the inductor, etc?

Thanks!

Posted by bill.french on 06 October 2010 - 11:18 PM in General Discussion

Posted by bill.french on 06 October 2010 - 12:56 AM in General Discussion

Posted by bill.french on 06 October 2010 - 02:16 AM in General Discussion

Posted by bill.french on 03 January 2011 - 08:25 PM in General Discussion