<***OFF TOPIC***>
Assuming you're a programmer, imagine a world where's just one language to create your applications. That language has no owner than the universe, immutable since the beginning of the time, also will have no upgrades, nor evolution. You'll be granted it keep the same forever.
There are few rules, very well described, together with few tools. You know, few tools, but *good* tools. You may create everything with these tools.
There's no fuzzy depiction of this world: it's a well-ruled world called physics.
Welcome in the hardware world!

EDIT: I forgot to mention that IT HAS NO BUGS AT ALL!

I am an EE, but I love programming as well. I began over 30 years ago with software, and I must confess that I STILL HAVE A FUZZY PICTURE OF THE SOFTWARE WORLD!
</***OFF TOPIC***>

Inquisitor, both Stefan and ItsDan gave you good tips.
Your idea to use a CD4067 (16-1 mpx) is good as well.
Cheers.

Hi Mario,
I enjoyed your “Off Topic” … I think I detected a little sarcasm… because we all know Microsoft coding is bug free!
I guess I’m your double ganger with 30 years in the software world. … And… with a strong dose in Physics/Engineering. If I could have hooked up my computer to the real world, sensing and moving things in the price range this Netduino does, 30 years ago, I’m sure my life would have way different!

In my simple view of EE, I see… I just “tell” the CD4067 which sensor I want data, and then read the data on the single analog input. I just treat it like a big switch. I can deal with that!
I really liked Stafan and ItsDan idea as dealing with a com port is second nature to me… and again it would be my hardware limitations that shy me away from it. I don’t see how to get 15 of these little $1.13 sensors into a serial output… OR… having to pay a lot more for some equivalent sensor that does it for me and then get 15 of them.

Stefan,

The more I read, learn, bookmark and… then… note who the teacher is… your avatar seems to come to mind the most. Thank you for sharing your expertise (and learning curve) here, all over the forum and on your personal web site.

I’m a software type with a real fuzzy picture of the hardware world. I currently have a little science project I want to create. I have scoped it out so far, such that I need…

• (4) PWM Outputs to control servos
• (15) Analog inputs to receive various sensory input (if it’s significant, I’m currently looking at a mix of IR Optical Detectors and Ultrasonic Range Finders)
• (~8) Digital outputs to light various LED’s for status and/or warning indicators.

From my simplistic concept of Multiplexing… it allows me to time slice between far more inputs or outputs than I have on the Netduino. In your example above, you have both inputs and outputs. But before I go and make an ass of myself for assuming something… does you example work for analog inputs?

If I understand correctly, could I move the purple wire from Port 12 of the Netduino… to Port 0? And then in the software read from this analog input instead?

Thanks your your help.

Thank you for your response...

I guess I need to learn how to wire something up like this...Serial/Analog Mux/Demux - 74HC4052 ...
... or better yet... 16 Channel Multiplexer


... it turns out they even have a wiring example with an Arduino for us hardware challenged individuals

Basically, the value of the resistor determines whether the transistor operates in "active" (i.e. amplifier) or "switch" mode, it is also used to calculate the load current, which for example application is about 1 mA (I_C = V_CC/R_L, where Vcc = 5V, R_L = ~5kΩ). For more detailed information, you may want to check out Design Fundamentals for Phototransistor Circuits (pdf), Using the Transistor as a Switch, Transistor Circuits, Common collector and Common emitter.

OK... I couldn't wait. This first document was exactly what I needed!

If I reading the datasheet correctly, the Icc in the article is Collector Current Ic(ON) that is on the datasheet and is 1 mA. If I want to use the Netduino’s 5V output, this gives me the crossover point from Active to Switch mode at 5kΩ. So for the tachometer (just counting off/on cycles) I should use resistors higher than 5kΩ (for Switch mode) and for measuring distance, I should use values less than 5kΩ (for Active / proportional response). I’m good so far?????

What about the other extremes… I’m guessing at real high values of resistance their won’t be enough current to do anything. Likewise, at real low values of resistance, I’ll either be pulling too much current from the Netduino board (200 mA) or pushing too much through the phototransistor. Is there something on the datasheet that will keep me safe at both ends?

In my best Dalai Lama pose… Ummmmmmmmm… keep the smoke in the chip…. Ummmmmmm!

Just FYI. I don't know if this will be useful to anyone...

I'm not sure what I've got going wrong. My data seems to be opposite what "Design Fundamentals for Phototransistor Circuits" said should happen. 5.63kΩ is the calculated resistance for the cross over from Active Mode to Switch mode. However, using 9.52kΩ seems to be the most proportional (but not really very), while the low resistance 1kΩ acted closer to a switch. I also tried 1MΩ and nothing changed.

Basically, I don't think its going to be usable for determining distance.

No, it's not, because as you can see in Normalized Collector Current vs. Distance chart in the datasheet, the device peak sensitivity is around 20 - 30 mils (0.5 - 0.76 mm) and decreases significantly, at 200 mils (5 mm) is is only 10%. You'd need to choose different sensor to measure larger distance, such as Sharp IR proximity sensors, or you can make your own - just use IR LED and phototransistor (very cheap) that has matching wavelength (850 nm, 940 nm etc.).

Another option is to use IR photodiode instead of phototransistor - the photodiode has faster response time than the phototransistor (orders of magnitude), but produces significantly lower current (typically tens of µA), so an amplifier circuit (OPAMP) is needed for interfacing with a microcontroller.

Also, for IR distance measurement in noisy environment (the sun is a strong source of background IR noise), you'd need to use modulated signal (e.g. driving the IR LED with 36 - 40 kHz PWM signal) and either demodulate the received signal or use IR receiver module that has it built-in (e.g. TSOP382).

I’ve always been comfortable with graphs in my former profession… material stress/strain curves, damped vibration and stuff and I should be at home with these curves. But when I look on page 2 and see the first line item: Forward voltage @20 mA, Max value is 1.7 volts… THEN I look at the first graph Fig 1 on page 3, I have a major disconnect… I see at 20 mA… maybe 1.22 (mA sic - should be Volts) and as far as I can see, it’s never going to make it to 1.7 Volts. Either way… they just don’t jive. I guess... I didn’t go any further in the curves because I didn’t have any trust in my ability to interpret what they meant to me in the real world (since I couldn’t get past that first one).

Also, I guess I was trying to achieve something usable at 3 cm since the “bildr” tutorial above said I could (should). But now that you point out Fig 5, I see your point and won’t keep trying to make it do things outside its intended function.

Thanks for the help!

Thank you all three of you! I look forward tonight to digging into your references (Bill’s transconductance and CW2’s links).

Mario,

Your sensitivity suggestions are definitely something I would like to explore. The tutorial above hints that the sensor should be good reading out to about 3 cm. In my last science project with the Tachometer, I didn’t have any luck beyond 5 mm. Unfortunately, for the tachometer, I was in the realm of sensing 2100 Hz changes, so 10 KHz strobing of the emitter, would really whack-out my software algorithm… probably get some kind of harmonic artifacts. (re-reading... maybe that's what the band pass thing you mention does… Note to self: research “band pass” circuit)

HOWEVER, for what I’m after now… I want to get the analog readings to measure distance. I’m hoping to see their 0 to 3 cm on the 10 bit A/D input.

I apologize for the correct terminology in English: in Italian we're using certain terms.

Sometimes (and very rarely) I have to pause and concentrate on what you are trying to say. But… your English is orders of magnitude better than my Italian! Hell! I understand you better than most Yankees!

Why, if your power is +5V, the output can reach +5.5V?

5.63V – I’m not quite as secure in my circuitry as you hardware types. (Just because I’m paranoid doesn’t mean the smoke isn’t trying to get out ). I have my little test rig hooked up to volt and current meters and a 5 Volt power supply that reads 5.63 V all the time.

I tend to suggest the experimental way for the resistor. Here's why...

Normal transistor (NPN).
If you make a current flowing FROM the base TO the emitter, say it Ib, then the current flowing FROM the collector TO the emitter, say it Ic, is:
Ic <= Ib * hFE
where hFE is a (pretty constant) parameter specific to any transistor model. Typically is around 200.
Now, notice the above formula:

• WHEN happens the EQUAL sign, the transistor is working in the ACTIVE area;
• WHEN happens the LESS-THAN sign, the transistor is saturated;
• WHEN Ib is zero, Ic is also zero, and the transistor is off.

I apologize for the correct terminology in English: in Italian we're using certain terms.

Photo-transistor (NPN).
Since *ANY* bipolar junction is also photo-sensitive, a photo-transistor is not much different from a normal one. It only provides a larger silicon exposure area to the irradiation, and/or others features we don't mind.
Typically there's *NO* Ib (i.e. the base lead is left open), so -apparently- the transistor should be always off.
When the light (stream of photons) is hitting the silicon surface, it acts as it was a current Ib. The stronger is the light energy, the higher is the equivalent current Ib, and the formula can be applied. The actual problem is HOW to calculate the Ib from the light radiance.
Of course there are formulas on it, but I would avoid ton of theory and missing parameters, side-effects, and whatever else. I'd prefer to choose a certain emitter, avoid (or establish) the surrounding lighting, then choose the best resistor by picking among a range.

Using a photo-transistor as on/off (sat/off) will require a very good exposition to the emitter, and a good isolation from any other (spurious) irradiation. A typical usage like this is in the old floppy-disk drives, to detect whether the read-only hole is open or not.
In such a circuit:

• the emitter and the detector are totally closed into the drive box (so no spurious irradiation);
• they are very close each other (no more the thickness of the diskette);
• they are perfectly aligned, so the rays hit the silicon with the maximum efficiency.

In other situations where you cannot rely on these models, you must use the photo-transistor *ALWAYS* working in the active area, consider very small output variations (e.g. millivolts), then amplify, maybe filter as well.

Your suggestion of using the experimental way is a very good one (and certainly for me). I think I need to get “dirty” just trying things so I can start to get a feel for what can and can’t be done. I think that is why I rigged up the above equipment. I was pleasantly surprised that my test rig gave me such smooth data and rational data. I was expecting to have more outliers. Way cool! I’m liking this hardware stuff!

Not long ago I built a circuit using a led and a photo-transistor to "read" the blood pressure heartbeat within a finger. May this circuit be useful for you?
Cheers

I would be very interested in your heartbeat sensor. I just not sure, I’m up to understanding how it works… yet.

Thanks for your help.

Hello Inquisitor!

For hackers & micro dudes, I would keep a stash of 1K, 10K, 100K, 220 & 350 ohm, resistors. That will do you very fine! Everything "digital" can be handled with these resistors.

Regards.

I guess I am a wannabe dude... Not knowing ahead of time what I would need over time and picturing myself spending hundreds of dollars in gas to buy 1's and 2's at radio shack, I just got the 73 Values Set. I'll probably never use 90% of them. But... My little one liked sorting out the colors and categorizing them into a plastic drawer case. Also, I've been playing around with serializing and paralleling them to get exact values calculated by the equations. It appeals to my anal-retentive side.

Software type needing training wheels…

I’m playing around with a QRD1114 Optical Detector (Basically a combined Infrared LED and Photo Transistor). Here’s the demo, I started with… Tutorial and here’s the datasheet. All works as advertised.

Now, I’m trying to dissect how to do it without the cookbook.

On the LED side, I’ve got it figured out as a current limiting circuit and have calculated and tried it out at several supply voltages. I’ve got it instrumented up with voltage and current readings and I’ve matched the calculations and kept the smoke in the chip!

On the sensor side… I’m at a loss. I’ve Google searched and there are plenty of other examples like the one above, but no one is revealing the magic behind the curtain. I want to figure out how the 4.7k to 5.6k resistor is calculated from the data sheet. My request is twofold…

• I want to be able to determine this for other similar sensors I might use in the future.
• I also would like to figure the total range that the sensor can handle. The cookbook

above suggests that changing this can adjust the sensitivity. I would like to hook a potentiometer up to it with this calculated range and see how the sensitivity changes.

If you feel the question involves too much digging into the datasheet above, maybe you could help me with the key phrase (like “current limiting LED”) that might help me find the solution.

Thanks for any light you can shed.

I've a problem working with UART. I'm using SerialPortHelper library. But I can only write, not to write anything.

Here is my code: ...

As Mario mentioned, the variable named "line" is not defined. But then your compiler would have told you that... so I'm guessing it was accidentally deleted when you posted the code.

You might also add a little more information... like what behavior you are seeing besides "But I can only write, not to write anything." Either you miss-typed this sentence or you are struggling with English as a second language. I'd be glad to help, but I need a little more to go on...

OK, I've tried it now with some hardware.

If you are just trying to mess with the serial port code in general on the Netduino and intended to have it talk to itself, you need to connect a wire from port 1 to port 2 on the digital side. Once you do that, your code will work fine. However, If you did that, you’ll also find that there is no indication that it’s working. Once I added the Debug.Print statement below, you can see that it’s receiving.

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

namespace SerialPortLearn
{ 
    public class Program 
    { 
        static SerialPortHelper serialPortHelper1 = new SerialPortHelper();
        
        public static void Main() 
        {
            serialPortHelper1.PrintLine("Initializing..."); 
            while (true) 
            {
                string line = serialPortHelper1.ReadLine();
                if (line.Length > 0)
                {
                    Debug.Print(line);
                    serialPortHelper1.PrintLine("Readed: " + line);
                }
            }
        }
    }
}

If you are trying to interface with some other device… like a computer, then I can tell you, your code is fine and then the problem is with your wiring to/from the computer or the computer software on the other side.

Good Luck!

That sleep thing isn’t overrated.

This code (at least) compiles. There are several things in it I wouldn’t do, but I don’t see any show stoppers. Your example only uses the one port for sending and receiving, and since you’re sleep deprived… I have to ask the obvious:

Have you got Netduino wired to feedback on itself?

Here’s an example I wrote to test the serial ports, but it uses both serial 1 and 2 on the same Netduino. I know it works, if you wire it up as indicated in the text. Serial Port Communication

Let me know either way… if you’re still having troubles this afternoon, I’ll look at it when I get home.

Good luck

I really like the pinout card that came with the mbed. As i haven't found anything similiar for the Netduinos, i created them myself. The diagrams are quite large in the PDFs, please scale them to your needs when printing. If someone spots an error please post it so i can correct the diagrams.

Tecchie

Thanks! These are great.

I would perform the test up to +15V, which is above the car supply range. It would be useful to connect directly to the car outlet.
Cheers

I second this! I was wondering the same thing... when it says limit to 12 Volts, but cars routinely show 14+ volts when charging.

IF I understand you Chris... The issue is not the voltage (up to 20 V), but a matter of what I'm driving off the Netduino pins and thus trying to pull through the voltage regulator(s) on the Netduino board. As long as I'm using small, low current stuff, I should be ok on a car's voltage system?????? Or am I overly simplifying things too much?

If so, I'm guessing there should be some upper limit of current... would that be the 200 mA on the specs... or something less? And No! I wouldn't hold you to it... if I fry a Netduino by putting it on a car, its totally my fault.

...
It would be interesting to get some feedback from members as to why they zeroed in on the Netduino. ...

For me it was a no brainer... working all day with Visual Studio in my day job and all home projects as well... Windows Phone 7 apps, engineering apps for my other bad habits... designing boats and etc...

Also, have a friend at work and after watching five minutes of him dink'n in the Arduino editor and I was sold! People can give Microsoft grief on many things, but I haven't seen anything touch Visual Studio (Eclipse included)... but then I might be biased

And I'm glad I did... the Netduino... JUST WORKS!

I just wish the hardware side was as falling off the log easy. Maybe someday.

Allow me to introduce myself:
...
I have a reasonable good handle on programming with VB.net and to some degree also C#.

Welcome!

I saw your post yesterday and was going to respond, but I knew there were far more qualified members… I FEEL YOUR PAIN… Daily.

Sleep Tracker – Many of the SparkFun pages have references to tutorials. It just so happens the accelerometer you picked didn’t. But this one did… 3-axis accelerometer

Typically under the Documents section, they will have a tutorial…


I don’t know… but you might find the pin-out to be similar to what you have. And although, it’s taught to go to an Arduino, the pins on the Netduino are pin compatible so the wiring should be the same on that side. Although, the software samples are C++ and the objects are different, I suspect that you’re probably more comfortable with the code side (like me) once you have the wires in place.


Window Blind – If I understand your needs, you’ll want to know where the blind is as its moving. There are many ways… you could use a stepper motor so you know exactly how many rotations to lift the blind. I’ve gotten, but haven't used yet…

• Stepper Motor
• Stepper Motor Driver

...for that purpose. There is a tutorial on the stepper motor driver page. Another alternative might be since the roll up blinds might not roll up with same number of turns every time. I know in the real world they seem to roll up tighter some times than others. You might use a motor and motor driver and then use a reed switch/ magnet or optical sensor to detect when it’s up and/or down. I'm kind of partial to the optical sensor! Its way cool what it can do.


I haven’t messed with RF yet, so, I’ll pass to others…


Otherwise, have fun, ask questions when you get to more specific issues.

Good luck!

I really wonder why a programmer never asks for some source (book, web, tutorial, etc) to learn the electronic basis, so that he/she will "walk by him/herself".
I am *REALLY* happy to teach something to who does not know, and share everything I can of my knowledge about circuitry, but...why discourage?

WHOA! There is such a book????
I'm asking! I may have neglected to ask on this forum, but I have asked many of my EE friends and family. I can’t blame them they design CPU’s for HP so thinking with less a billion transistors is no longer an ability of theirs. Without exception, they have all pointed me to EE 101 type books that are theoretical based. I think I need something more technician based.

So if there is a book that could teach me how to create the trivial stuff you all take for granted like pull-up, pull-down, current limiting, how to use op-amps, voltage regulators, diodes, resistors, transistors… doing simple (~ less than 20 component) digital circuits… I would be eternally grateful!!!!!!

I shouldn't need to use GetMethods or GetParameters since I'm writing the code myself I will already know the Methods and Parameters for them.

That what is normally expected.

In my case, I was trying to make a Web Server, but I wanted it to support the MVC coding style for server applications. So in addition to hosting the easy html/script/resource files on the SD card I also wanted end-users to be able to have their own binaries. The server piece would then have to inspect the user's "Controller" classes, get their methods and parameters. I was "hoping" to do parsing of the request string into parameters and call their methods... just like MVC running on IIS. And I was right there... until I started looking for "GetParameters".

It was not to be. Dammit!

Is reflection supported? If so what about using Assembly.Load and then .CreateInstance

Sorry, didn't answer the second part... This works.

using System;
using Microsoft.SPOT;
using System.IO;
using System.Reflection;

namespace Sandbox
{
    public class Instantiate
    {
        private Assembly _ass;
        private object _obj;
        private Type _type;
        private MethodInfo _mi;
        private MethodInfo _ma;

        public Instantiate()
        {
            try
            {
                FileStream fs = new FileStream(@"\SD\bin\OutsideLE.pe", FileMode.Open);
                byte[] image = new byte[(int)fs.Length];
                fs.Read(image, 0, (int)fs.Length);
                fs.Close();
                _ass = Assembly.Load(image);
                _obj = AppDomain.CurrentDomain.CreateInstanceAndUnwrap(
                    "Outside", "ASSM.TestClass");
                _type = _ass.GetType("ASSM.TestClass");

                _mi = _type.GetMethod("Print");
                _ma = _type.GetMethod("DoSomeMath");
                _mi.Invoke(_obj, null);
            }
            catch (Exception ex)
            {
                Debug.Print(ex.Message);
            }
        }

        public long DoSomeMathExternal(params object[] args)
        {
            return (long)_ma.Invoke(_obj, args);
        }
    }
}

The object in the SD binary file

using System;
using Microsoft.SPOT;

namespace ASSM
{
    public class TestClass
    {
        public TestClass()
        {
            Debug.Print("TestClass Instantiated");
        }

        public void Print()
        {
            Debug.Print("Hello there");
        }

        public long DoSomeMath(int a, int B)
        {
            return a * b + b;
        }
    }
}

Its on tech page... in fine print

And the point... is for your prototype machine... one project may need networking, next might not... but need lots of space. So reload Netduino... reload Netdunio Plus... wah... la.

Thanks for the reply. This sounds promising. What is the largest SD card the netduino plus can support? I can see myself having the main application on the main memory and loading and unloading dll's from the SD as needed.

You got it. I know the current framework (4.1) limit is 2GB. Which is what I have. But I read that the 4.2 it tackling that one and various people have used at least 4GB. I haven't heard yet what the upper limit is going to be.

NOTE: Oh, also, I was looking at this method to handle the code updates for customers you mentioned. Its a whole lot easier (for the customer, not the developer) to just upload through the Internet via the Network connector and on down to the SD card, have the Netduino reboot and they get an upgraded application. Also, I noted that once the Application.Load() has finished loading, it doesn't lock the file... like the desktop does. So you can upload a new program even while the old program is running! Way cool! Just got to make sure the resident program stub is bullet proof! Good luck. Take the plunge.

MrSmoofy,

GOT to be a story behind that name!

I know I had a lot of the same concerns before I actually got a Netduino Plus... especially since it has even less room due to its support of the networking and SD card. But I’ve been surprised at how small the C# code I write is compiled down to before installing on the Netduino.

You can use an SD card for additional storage of resources, but not code space. That has to stay within the limits.

Colin, I’m not sure that is correct. AND, I’m not 100% sure I’m right either… AND IT’S A REAL PAIN IN THE ASS… but,

In the old days (aka Stone Age, IBM PC running a whopping 4.77 MHz) you had to segment out your code into sections. When you needed certain functionality, you dynamically loaded that off the hard disk floppy disk and ran it. Once done, you chucked the code and loaded some other over it and continued on. I played around with the Application.Load() method and got it working to do the loading and running side. The part I may be way off… I didn’t try unloading it. Being Managed code, I would assume, killing the reference will unload it, but I don’t know that.

Now… if you are needing all your code in the 28K memory at once, OR can’t live with the delayed loading, then basically… I’d have to agree with ColinR… you’re basically SOL.

If anyone is interested, I’d be glad to try and do that loading/unloading thing and see how large a program I can get into OFMME (Old Fart Memory Management Engine).

Would anyone happen to have a large C# code base they want tried?

I thought I should comment... Having 2GB of code on a Netduino... Hmmmm.... maybe we need to evaluate our hardware paradigm. Also... unless you're my age, programming since the (mid 70's) you probably don't remember how abrasive this kind of segmented programming is. At least we had 64K instead to work in. And I don't even know if I could un-wrap from OOP principles... because it is decisively back to a procedural programming style.

Is reflection supported? If so what about using Assembly.Load and then .CreateInstance

Some reflection is supported. I was going great guns on a project, until...

You can find methods on an object, but you can't query for parameters.

Type typ = GetType();
MethodInfo[] methods = typ.GetMethods();
ParameterInfo[] prms = methods[0].GetParameters();  // <==== This doesn't exist.