Was just about to go to bed and saw this thread. Downloaded the beta framework and installed. Two days ago I downloaded and installed the retail VS2012 Professional. Microframework applications in my solutions now load. I built a 4.2 netduino+ application, deployed and debugged, working fine so far. Will be putting this to a hard test over the next few days and hopefully will be able to do away with 2010.

I recently moved to 4.2 RTM to take advantage of the reduced networking byte-code size which I read about in a forum post on here somewhere. Where does general information about new microframework footprint sizes come from?

I don't seem to be able to find the 30cm go!cable's for sale anywhere. Does anyone have a source? I need the length for the location of the touch screen in this project.

You can make these kinds of things really easily. They require no soldering and you only need tools to do it if you want to make it easy for yourself. The Netduino Go uses standard 10-way header sockets(5x2 pin array) that have locator notches. The items you need to make cables are:

• 10-way plugs (one per end if required)
• Ribbon cable (grey or multi coloured are fine)
• Clamping tool (less than $10 and reduces chance of mistakes)

You can get all of these from electronics hobby shops and electronics parts retailers/suppliers. The 10-way plugs usually come packaged individually with three parts to them. The larger part has sharp contacts that pierce the ribbon cable wires when you clamp it. The other two pieces clip into the main piece. One is smaller than the other. The smaller one is used to clamp the ribbon into the sharp contacts. Line the ribbon up with the contacts and push down hard with the second piece(using the clamping tool makes this really easy). Once clamped, fold the ribbon back over the plug and use the final piece to brace the ribbon. It prevents tugging from ripping the ribbon out of the plug.

The ribbon cable can be bought in lengths you require. If you can't get ribbon with 10 wires in it, just buy anything larger than that. I personally have a massive roll of 16-way that I use for everything and strip off what I don't need for a particular cable. Sometimes you can buy bundles from electronics hobby shops which have breadboard wires and ribbon cable in them with other junk if they don't sell ribbon cable.

Not sure what country you live in but I've never seen these cables pre-made purely because they're not used in consumer electronics for external purposes. I have read that packs of 10-way cables for the Netduino will be sold soon within the USA for people who aren't hardware savey. Not sure what the status on that is.

Thank you Mario for your response.

I know that the framework slows things down..But most of teh time the developper is the problem!

But I know that on a PC, the differences is sometimes hard to see..
The conversion time of an ADC can be less than 5 Microseconds..
A simple loop with simple calculation run very fast.
It is the call to the ADC which goes wrong.
Usually, it is possible to start conversion, than to read the result later.
With NetDuino, it seems that we have to start and wait conversion..
Even though, response time is very long...

What I want to to is to store data from 1khz ->10khz signal into memory, and dump it from a PC.
It works fine for 100hz signal..


I will work on it...

If you configure the ADC to operate in free-running mode, the contents of the ADC register is constantly changing for you at the maximum rate the ADC will operate at. This kinda eliminates conversion times from a hardware interrupt. There are two probelms with a free-running ADC.

If you strobe multiple pins you run into parallel operation errors. I haven't checked the SAM7 architecture but most AVRs only have 1 ADC but have 5+ pins you can strobe off. When you change the ADC strobing register to select another pin, it might be impossible to determine which pin the ADC data register contents belongs to if you read it immediately or shortly after. Some AVRs don't allow free-running with strobing.

The other issue you have is when you read a sample from the ADC register in free-running mode, you don't know how "old" the data is. When you take two readings, there will always be a degree of skew in your measurement windows which increases with a slower ADC sampling rate.

Those two issues aside, it's also a tall-order to measure a time interval less than 1ms accurately.

I understand this might be a difficult ask because of how taxes and tariffs work in various countries but I was looking at being able to purchase Netduinos from overseas. There's only one reseller in my region and they have recently been 'less than helpful' with the loss of and expensive package. I would prefer not to do business with them anymore if possible and I'm a month or two away from a green light to purchase a commercial quantity of Netduinos for a client's project. I've tried using Amazon and a few other resellers and they have international shipment policies in place to prevent purchases for whatever reasons/structures you have in place with your distribution network. This has probably been asked in a few threads but have Netduino Plus 2's been shipped to most international resellers? I would be looking at moving my product's hardware platform from Netduino Plus to Netduino Plus 2 and would like to do an evaluation before buying a bunch.

Hi Nobby,

Which region do you live in? Also, sorry to hear about your bad experience. Is it a Netduino-reseller? If so, it may be good to know for Secret Labs which reseller.

I'd prefer not to put the particulars of the issue on the forum. Is there an appropriate email contact at Secret Labs I could shoot my email off to?

I have used only Nwazet and Proto-advantage for all my stuff, both give you cheap delivery, and reasonable fast shipping.
I'm always taxed on those purchases though, since Norway have this stupid customlimit, if it cost above 200NOK (about $32) I have to pay 25% on everything including shipping.

When I bought an Arduino now, I tried to buy from the italy shop, kinda, to support buying from correct place, but they did not trust the postal system, so they required me to use an $77 UPS shipping. So, of course I bought it from Adafruit instead, which sold me the unit at proper price, and $9 in shipping
Most of my electronic stuff is coming from the two above, pluss ebay, and adafruit.

I feel your pain. My country has horrible software tariffs with the USA. Our currency is stronger than theirs but my MSDN subscription costs me nearly twice as much as a US subscriber. I don't even order DVDs, just download everything.

Hi Guys,

As I have exhausted all the Digital Pins for all my pulse counter and communication, now only left with the Analog pins untouched. May I know is there any way I can use the Analog pins for driving a LED (for machine status) purpose? also can it be configure to use to detect button press input?

Thanks in advance.

I have recently used a few of the analog pins for similar reasons as yours. I can confirm you can use them as TTL output pins and almost certainly as TTL inputs.

Just ensure the maximum forward current through each LED doesn't exceed 25mA(maximum pin current).

Good day everyone.

Any plans to have ParameterizedThreadStart available in the MF?


Thanks

You can use lambda expressions in conjunction with the standard ThreadStart class. It allows you to have type-safe targets as well.

class MyClass
{
     Thread myThread = null;

     public MyClass()
     {
         this.myThread = new Thread(() => MyClass.threadFunc(this));
         this.myThread.Start();
     }

     private static void threadFunc(MyClass myClassObject)
     {
            //do stuff here
     }
}

Target delegate doesn't have to be static either

If I'm using a dual coil latching relay with voltage of 3V (with coil resistance 129 ohms), do I need to use the transistor ??

It's a bit touch & go with your situation. When they say 129 ohms, they mean total impedance. Part of it is reactive and the other is purely resistive. 129ohms at 3.3V from the CPU pin will draw up to 23mA which is borderline. If you intend on driving the relay in short bursts then it would possibly be acceptable but otherwise you wouldn't.

Once the transient behaviour dies away from switching the relay on, the effective impedance of the relay will be less and you'll exceed the maximum continuous current draw from the CPU pin and smoke the poor thing.

If it was me, I'd use a transistor.

Hi Guys,

Separately, do you have any sample circuit to connect to N+ for measuring 4-20mA Analog input?
Together with sample code will be great. Currently I am using VB.net to handle the 12V pulse input through opto-coupler circuit.

Thanks in advance.

I don't think you can measure current with a microcontroller. You need to transduce the current to a voltage.

The most accurate method is getting a transducer which uses electromagnetic coupling. It's also the most expensive method.

The easiest method is to use a really small series resistance (1-5 ohms, whatever you can get your hands on) with the circuit you are measuring current. Measure the voltage across the resistance and divide that by the series resistance in your netduino code. The result has errors obviously. Adding resistance to the circuit changes the current. You might also get non-negligable current flow into the analog pin even if it has a high impedence characteristic during analog sampling.

The other consideration you need to be aware of is that 4-20mA is a rather small current to transduce. Mostly because ADC(Analog to Digital Conversion) usually has a precision relative to the operating voltage of the microcontroller(AVR/Netduino) and the value of AREF(usually set to zero volts or Vcc/2). A current that small will produce a voltage so small it will appear as zero after ADC. You'll need to amplify the transduced current signal significantly, especially if you are working in a narrow measurement range (4-20mA).

You can make a simple voltage amplifier with two resistors and an op-amp package.

Hello Alex,

Sound a typical field instrumentation problem.

Use a 250ohms in parallel to 4-20mA signal. Remember V=IR .... V=(4/1000)(250) = 1V...do similar
operation for 20mA and you get 5VDC...right in the acceptable voltage range of the Analog inputs...

Hope helps.

You can't measure the current of a circuit using a parallel impedence, that's only appropriate for voltage measurements(scale conversion). Parallel impedence splits the current through branched paths and it also alters the characteristics of the circuit in a large way(unless the impedence is essentially infinite, 250ohms is very low).

The current transducer circuit has to run in series and have a negligable impedence.

You've got two goals to achieve here. Your circuit build/hook-up and software to control the H-Bridge. The good news is that regardless of how you end up controlling the H-Bridge, the connections are the same.


You haven't specified what your H-Bridge is and how it's been put together etc. They're simple systems to understand. You need to connect at least three different kinds of connections:

• DC Bus link voltage. This is the power supply you provide the H-Bridge. It can be bi-polar or uni-polar but it depends on if your H-bridge will allow you to connect a 'center-tap' for setting the ground as a mid-point.
• CMOS/IGBT gate inputs. You connect your PWM outputs to these. There are four of them but they are in pairs so you only need two PWMs to drive it. One switch is always off when the other is on for each pair(side note on this)
• H-Bridge output goes to the motor. You will be able to drive a DC or an AC motor with an H-bridge.

There may be some other component considerations depending on the gear you've bought.

Controlling the motor can be as easy or difficult as you want and it's a massive field for you to explore. To start with, you will most likely be able to get a library or use .Net classes which will operate the PWMs for you. Because you have an H-Bridge you have two options:

• Use one PWM on half of the H-Bridge as a starting point. It turns your H-Bridge into a single phase-leg modulator which means you can't drive an AC motor
• Use two PWMs on the full H-bridge which will allow you to drive an AC motor as well as DC

Above is your starting point but it has no feedback control loop. Without feedback from the motor, you won't be able to know how fast it is actually spinning for a given input signal. If it's important for you to have precise control of the motor speed, you need software in your project which will measure the motor speed and figure out the difference in desired speed and actual speed the adjust your modulation depth to drive the H-bridge harder or less. Some motors can tell you their position as well so you can precisely control the position of the motor as well as speed.

Having said all this, if you're just a hobbyist and want to see the motor spin, you don't need a feedback control system or understand much about modulation theory. If you told us more about your goals then we can be very specific about helping you to setup the right system.



--edit: oops forgot the side note. Depending on how your H-bridge has been designed, you have to build a "dead-zone" into the PWM signal. If there's free-wheeling diodes and/or your H-bridge uses IGBTs, there's a discharge transient when the device attempts to switch off. If you toggle the other switch on before its complimentry switch has fully turned off, you create a short on your power supply every time the PWM switches on/off. It will damage your supply and possibly much more.

The most common options are UART(RS232 or RS485 from the PC to the netduino) or TCP/UDP network stream/packets. The second option requires either a Netduino Plus or a Netduino with an Ethernet Shield. You can also use I2C(TWI) and SPI but you need to build interfaces at both ends. I'm not even sure you can get something like USB->TWI or USB->SPI(apart from microcontroller programmers) that you can put at the PC to send data to the Netduino. As far as I know, you can't utilise the USB socket for runtime applications but I could be wrong about that. For the 7-Seg display side of things, the serial drivers are usually the best option. They require minimal GPIO pins from the netduino compared to other options. You need to make sure the current capacity of the drivers exceeds the rating of the 7-seg displays as well otherwise they'll heat up and die fairly quickly

The program is stored in non-volatile Flash memory(EEPROM). I haven't looked the modern longevity but you can expect roughly fifty years of reliable program storage in the device under desirable environmental conditions. Static electricity causing a wipe is a lot less likely with today's microcontrollers but still possible. It's more likely physical damage would occur before program erasure. The only controlled method of non-software executed erasure is from connecting a positive voltage(3.3V+) to the little gold square on the board. This configures the board for firmware operations until you repower the device. I'm not sure if this actually erases the program Flash though.

I have version 4.1 since this is what is recommended in the Download section of this site.



I tried all your suggestions and my browser still doesn't want to connect to the Netduino. I am running the example code from Chapter 8.



I really appreciate the it! Here is a screenshot of my current network settings in MFDeploy:

I noticed in your MFDeploy screenshot that your default gateway isn't in the same IP pool as the DHCP assigned IP address(192.168.5.XXX vs 192.168.1.XXX). Since you're using 24-bit networking, a lot of things are going to go south here. It also suggests that you might have some sort of configuration issue in the netduino or your router.

--Edit my bad: I saw that was your old static IP address.

I use the DFRobot GPS shield based on the UBlox GPS unit but interfacing is the same. The first change you'll want to make is how you read the data. The GPS unit will constantly send NMEA and UBX packets to you. It could also send packets of other GPS protocols. With UBX in particular, the packets start with a deterministic pattern.

Sometimes the data can contain characters which are non punctuation, letters, numbers etc because certain bytes are acutally bit-fields of configuration and satelite data. String constructors might return NULL based on these non-alpha numeric characters. Instead, make a string, use a for/foreach loop and append each byte onto the string but cast it as a char.

change this

Debug.Print(new string(Encoding.UTF8.GetChars(buffer)));

to this

string dataString = "";
foreach(byte b in buffer) dataString+=(char)b;
Debug.Print(dataString);

Good luck

Well, I understand the concept and I dont have a problem writing the code for say a 2.4GHz processor x86 with a 4 GBs of ram sampling time of around 1e-6 second easily, the problem I had over here was using this high resolution encoder with a netduino thats all. Just to put things in perspective, if the shaft is rotating at 3 revs/second (180 rpm which is not much )thats 1200*3 = 3600 interrupts/second. I just need help on generating an efficient enough code for the netduino to be able to handle all that along side of some computation thats all. Like I said I am just not used to micro-framework.

There's a couple of ways you can deal with your scenario. If your PID controller is for speed only then the only problem you'll face is convergence speed and possible overshoot depending on your performance specification. Even if the interrupt frequency basically matches the transport delay of the netduino hardware/framework, you just design your PID outer control loop as fast as the device can.

Position control for 3600 interrupts/sec is going to be hard. Depending on how smooth the control needs to be, you would probably have to slow the motor down. If you have to maintain a particular speed range then you'll most likely have jerky position control from lack of controller bandwidth and transport delay.

Although the netduino is capable of 100ns precision timing, most timing functions have 1ms precision. Do you have an option of a lower resolution encoder or do you need to have ridiculously fine position control?

One method I use is to create a socket which is a listener using IPAddress.Any for the binding. The listener will be created if the network is up or down but you can call Socket.Poll(). It will throw a SocketException if the network is down with an error code 10050. The only time this approach fails is if you power the ND+ up and it initially isn't connected to the switch/router. There's some bug which is apparently being fixed in 4.3 where network connectivity to the ND+ is impossible under this start-up condition but the ND+ internally believes connectivity is fine after you plug the network cable in.

I was about to start prototyping code in my existing product to use SSL for client authentication. Haven't written I line of code yet but I've read through the framework API for supported functionality. http://msdn.microsof...y/hh401316.aspx is where most of what you need can be read. I'm not sure if this component of the .Net Microframework is part of the build for Netduinos.

The basic run-down is that your device can be a client or a server as far as SSL is concerned so technically you can pull off HTTPs. If you're using basic HTTPS then you only need to store one or two certificates. One to certify your netduino as a secure server and possibly another certificate/cert chain that points to a publicly trusted certification authority(CA). If you don't care about the certificate being trusted and you just want secure communications it's pretty simple.

• Generate and store the SSL certificate for your netduino into RAM at run-time via the CertificateStore class. Put the cert on an SD card and read it off each time you boot up
• Use the SSLStream class for reading and writing data instead of a NetworkStream with the client socket.
• Server authentication via the netduino certificate is mandatory but client authentication with a separate certificate is optional. Use the SSLStream.AuthenticateAsClient and AuthenticateAsServer functions.
• Once authenticated, you use the streams like normal HTTP

Hey crawf, I'm about to head to bed so I'll read this thread tomorrow. Judging by your code, the methodology is fine. I use I2C comms with a GPS unit and i've tried various approaches to see how flexible the API is. The main points you need to know: -When you perform a write operation, .Net will ALWAYS provide the device address in the transaction, you don't have to add this to the byte[](not that you are but just so you know) -When you perform any transaction, if zero actions are returned from Execute(), this means that communication to the device failed completely. This has nothing to do with register addresses -.Net handles all ACK & NACK signalling(comms interlocking). The number of ACKS & NACKS returned by the slave device determines the return value of Execute(). -You can't simply read a single byte in a transaction. The data you read from a target register needs a destination array large enough to fit it. If you don't know the size required, give one sufficiently large enough. The remaining bytes in the array are set to zero(or a value defined in the device documentation).

Hi Nobby,


There appears to be a bugfix in lwIP to correct this type of issue. .NET MF 4.3 is getting an lwIP upgrade, so we're hoping to have a fix for this soon. [lwIP is a big complicated project and 10,000s of boards rely on it working properly...so introducing the update in beta firmware should help it get some good in-field testing.]

Chris

Thanks for the information Chris

I'm also having ethernet issues with the latest firmware. Although, I can't confirm if the issue exists with older versions. I discovered that the ethernet interface never works at all if a network connection doesn't exist on boot. I made a thread here: http://forums.netdui...h__1#entry32165 Nobody has shared any discussion on the matter. I'm using static IP in this case and absense of network connectivity is fine as long as it occurs after boot/powerup.

Technically you can do this. The first problem I thought of that would make me abandon the project would be that setting the alarm time would be a pain in the butt. Changes to the time are always relative to the previous alarm time so unless your netduino knows the previous alarm time, it is impossible to set a new alarm time. Unless of course you reset the power to the clock before the alarm time is set. Unfortunately, you'd have to setup the clock time as well as the alarm time. Secondly, you might have rate and synchronisation issues. For example, you know that if you mash the buttons as fast as you can, the clock will only change the values so quickly. The clock circuitry most likely polls for button presses as well and it's likely that you will occasionally have an adjustment pulse missed and the time you set will be incorrect. These are problems that I came up with before even considering the rediculous amount of electrical interfacing you need to do with the clock. If you're doing it for fun or learning, I reckon it would be great but practically, it would be a nightmare.

I'm putting together a simple class to handle multiple port interrupts through a single event handler. .Net microframework says that data1 can be the port number. I setup an experiement to evaluate data1 with two different buttons. I used D6 & D10(PWM1 & PWM3). PWM3 came up as data1=54 and PWM1 came up as data1=52. Comparing those to the Netduino schematic, the difference in the two numbers matches the difference in pin numbers(diff of 2) but the numbers don't match the schematic pinout. PWM3 is 67 and PWM1 is 65. Regardless of whether this is an error or not, I still need to build a relationship table. I would like to know if these are going to change in the future though for whatever reason. Is there an error in the designation of pin numbers/labelling on the ARM7 netduino schematic?