Hi Albert,

You should always .Close() the stream to ensure that all the writes are completed. Modify the loop to collect a finite number of samples and then close the stream when the loop is done. Flushing will push the buffer to the stream but not the underlying encoder which may still contain data.

See if that cures the problem.

Also, you should really define the scope for the using statement otherwise there's no point in having it:

using (StreamWriter w = new StreamWriter("abc.txt"))
{
    ....
}

With your code structured the way it is, the using statement is redundant anyway, you may as well just declare the StreamWriter without it and let the GC take care of it when it gets disposed at the end of the method.

Hope that helps.

- Adam

The scope of his using is the entire while statement that follows it. (The indentation may have been misleading in this case.) "using" is like "if" or "while" in the sense that it can be used without braces, though just as with if and while I would encourage the style of always using braces.

Yes, I realized that. My point was that without explicitly defining the scope the object isn't going to get disposed any sooner than the end of the method. He mentions in his post that he's a C# newbie so I think it's quite possible that he wasn't even aware of the scope issue and I figured it was worth pointing it out.

I'd like to vote against this advice for a variety of reasons. The StreamWriter object is not guaranteed to be collected at any particular time such as the end of the method (in fact, there's no particular guarantee that it will ever be collected), and even when it is collected, because StreamWriter has no finalizer, the Dispose() method won't be called anyway. As a programming practice I'd like to encourage you keep using 'using'.

What advice? I explicitly stated: "you should really define the scope for the using statement".

I wasn't advising against the use of using at all, I was simply pointing out why a scope is necessary. My entire point was to encourage the correct and explicit use of the using statement.

Apologies if that didn't come across clearly in the original post.

Hi Michel,

There are a lot of ways to do file I/O depending on what you need to do. Here's some code that I'm using to read/write to the SD card on the Netduino:

using System.IO;

public byte[] Read(string fileName)
{
	byte[] buffer;
	using (FileStream file = File.OpenRead(fileName))
	{
		buffer = new byte[file.Length];
		int bytesToRead = (int)file.Length;
		int bytesRead = 0;

		while (bytesToRead > 0)
			if (file.Read(buffer, bytesRead, bytesToRead) == 0) break;

		file.Close();
	}

	return (buffer);
}

public void Write(string fileName, byte[] data)
{
	using (FileStream file = File.Open(fileName, FileMode.Append))
	{
		file.Write(data, 0, data.Length);
		file.Flush();
		file.Close();
	}
}

The only word of warning would be that the read buffer in the above code could overflow on a platform with limited memory such as the Netduino. The code really needs to check the file size before allocating the buffer and then chunk the data if necessary.

Conversion.ErrorToString()

I Think I can replace the last one with a catch (Exception e) in a try catch and using e.Message ... I am right ?

Yes, you're right, use a try...catch and parse the exception like this:

try
{
	// something...
}
catch (IOException ex)
{
	// Catch a specific type of exception
	Debug.Print(ex.ToString());
}
catch (Exception ex)
{
	// Catch any exception
	Debug.Print(ex.ToString());
}
finally
{
	// clean up here, if necsessary
}

Hope that helps.

- Adam

I just started to learn .Net (I know so many languages ... and yeah, I know, late learning) so give me time.

If I wait long enough, we probably could have it in VB.Net on .Net MF lol (I'm a VB fanatic, so easy to program) but I'll try it in C# ...

One word of advice, since you're just starting out with .NET - make sure you develop the code in a .NETMF (Netduino) project and not a regular .NET project. NETMF is a subset of the full framework and I'm continually running into things that I can do in one but not the other.

VB.NET and C#.NET are much more closely related than VB is to VB.NET. I found the transition from VB to VB.NET to be hard work mostly because of the effort required to learn the framework. The syntactic differences between all three are not particularly significant.

- Adam

And I am right in assuming that the FLASH memory access is automatic ? or do we need to do some special access to read/write to it ?

Yes, that's right (assuming your SD Card is compatible). Just prefix the path with \SD like this:

File.OpenRead(@"\SD\myfile.txt");

I'd be interested in that - I don't know anything about it but I'm slowly progressing towards building an autonomous robot and it sounds like this could be really useful. - Adam

Hi demonGeek,

Certainly possible. Nothing supported today, but if the USB host enabled it...

Chris

Thanks Chris. Certainly something to think about.

I'm looking for a good fast way for two or more Netduino's to communicate without the memory overhead of a network stack and without using the I/O pins if possible. USB might be a good way to go.

- Adam

With 4.1.2 already offering early USB client support, will USB communication between two Netduino's become a possibility?

Perhaps using a USB Host Shield like this one.

Thanks.

- Adam

I'm playing with some code to drive a Sparkfun Serial LCD and ran into some timing issues which caused a garbled display unless I put an 80ms delay (Thread.Sleep) between each write operation.

This was fine for testing but with the delay on the main thread it slows everything down whenever I write to the LCD. So I thought it might be a good idea to put the write operation on its own thread like this:

private void Write(byte[] data)
{
	new Thread(delegate { this._Write(data); }).Start();
}

private void _Write(byte[] data)
{
	this.port.Write(data, 0, data.Length);
	Thread.Sleep(80);
}

This code works fine as long as the debugger is attached but as soon as I deploy and reset the Netduino, the display ceases to function. The code itself is still operational (no exceptions, as far as I can tell) but the display thread doesn't seem to be doing anything. If I remove the threading and write to the device directly everything is fine again.

Is this expected behaviour? Is there some better way of doing this that I don't know about?

- Adam

_{[N+ firmware v4.1.1.0 ALPHA7]}

Have you thought about using a queue and a timer?

Have a class which holds the data and the timer. Provide an add method which adds data to the queue and starts the timer. The timer event takes data out of the queue and writes the data. If the queue is not empty it restarts the 80ms timer.

Regards,
Mark

Thanks Mark, that would certainly work.

I've also been wondering about some kind of thread blocking mechanism.

The Sparkfun serial backpack has an on-board buffer and the timing issues seem to be centred around marshalling the data to that buffer.

I'll have to play with it some more.

- Adam

I believe the problem you are seeing is because the code doesn't actually do what you want it to do. You want an 80 ms delay between writes, however in this code the writes can all end up stacked on top of each other. If this doesn't make sense, consider this example:

You're absolutely right, that's exactly what's happening.

Thanks for the help.

- Adam

OK, so this is a real noob question, what terminal emulator (free) are people using on Windows 7 64 bit to talk to the Netduino now that Hyperterm no longer comes with Windows?

TeraTerm on Windows7 x64.

Old and ugly but still works great. A bit like me really.

- Adam

This code works as I can see data being written to the controller using a spi bus monitor

This is the only way I can get the spi to work. The code will not work if the SPI.Configuration is placed like this SPI.Configuration SPIConfig = new SPI.Configuration. It creates the exception as you described above. I don't understand why

Hope this helps

George

Hi George

You're right, that makes no sense but I tried it anyway: still doesn't work for me though.

I think this exception is a catch-all for just about any unexpected condition and as such isn't very useful.

If you have SPI working with that code then I think I can rule out my code which leaves either the connections or the device itself. Unfortunately I don't have another SPI device to test with at the moment, I think I'll have to order something and then test against that.

Thanks for your help.

- Adam

I just want to instantiate an SPI object but I keep getting this:

An unhandled exception of type 'System.InvalidOperationException' occurred in Microsoft.SPOT.Hardware.dll

Here's the code:

SPI.Configuration spiConfig = new SPI.Configuration(Pins.GPIO_PIN_D8, false, 250, 250, true, true, 1000, SPI.SPI_module.SPI1);
SPI spi = new SPI(spiConfig);

What am I doing wrong?

 
EDIT:
I've been looking at this for a while now and I'm beginning to wonder if this error might indicate that there's a problem with the connection to the SPI device (or the device itself). The device is this flash memory board connected as follows:

CS# <-----> D8
SCK <-----> D13
SDI <-----> D12
SDO <-----> D11


I've also tried (unsuccessfully) connecting the BUSY# pin on the board to D7 and then specifying that in the other constructor overload:

SPI.Configuration spiConfig = new SPI.Configuration(Pins.GPIO_PIN_D8, false, 250, 250, true, true, 1000, SPI.SPI_module.SPI1, Pins.GPIO_PIN_D7, false);
SPI spi = new SPI(spiConfig);

_{[N+ firmware v4.1.1.0 ALPHA7]}

Here is another idea to try. Since spi is basically a shift register, what you write you should be able to read. You can test the spi controller
and your code by connecting MOSI and MISO (11 and 12)on the Netduino+ together. This removes the slave device from the loop. The clock line and the device
won't matter, but disconnect them from the device anyway. Try this code:

George

Thank you very much! Your loopback idea put me on the right track to solve the problem.

I had been playing with a motor controller last week which was using a static singleton class that locked D12 before my SPI code ran. When I first tried your code it didn't work so out of desperation I created a completely new project and suddenly the code started working. After that it was just a process of elimination to find the offending code.

- Adam

**bump** Anyone have any ideas? I'm completely stuck on this one - I don't know if it's the code, the connections or the device itself. Any thoughts would be appreciated.

I use the Salae too, it works very well and I like the user interface.

Anyone got any thoughts on the Parallax PropScope?

It's not particularly cheap at $200 so would it be better to simply spend the extra on a dedicated scope instead?

- Adam

I believe that 3.3V is the maximum on the analog pins so 5V is going to max out the reading at 1023 all the time and skew the results.

When I tested at 3.3V I was getting much better data but there was still a wide variance so I hooked up an external AREF (connect the 3.3V line to the AREF pin) and switched on the external AREF in the code. I also averaged out the result and found that after a dozen or so samples it stabilized at close to the right value. Here's the code:

// Rev B boards use internal AREF by default: switch to external AREF
OutputPort arefSelect = new OutputPort((Cpu.Pin)56, false);

AnalogInput A0 = new AnalogInput(Pins.GPIO_PIN_A0);

const float vIn = 3.3F;
const float rKnown = 10000;
float rTotal = 0;
int samples = 0;

while (true)
{
	float vRead = ((vIn / 1024) * (float)A0.Read());
	rTotal += (rKnown * ((vIn / vRead) - 1));
	samples++;
	Debug.Print("Resistance: " + System.Math.Round(rTotal / samples));
	Thread.Sleep(1000);
}

_{[N+ firmware v4.1.1.0 ALPHA7]}

If you want to use floating point division, at least one operand as to be a float.

Tecchie is absolutely correct. I should have mentioned that I modified your original code to explicitly type the variables.

Personally I dislike using var unless there's no other choice. I prefer to make my code as explicit as possible because it leaves less room for mistakes.

As far as the AREF is concerned, I don't know how the Fez Panda works but the Netduino has an internal AREF (on by default) and an external AREF pin. It seemed to me that I got better results using the external AREF but I didn't really test that much so it might not be the case. Either way, you need to understand how the Fez Panda's AREF works otherwise the A/D conversion will be off.

- Adam

I get more or less the same result, it might take a bit longer (it is hard to say) but still runs out of memory at aprox the same pace.



I am pretty sure I am getting much more data than what I am consuming -through serialport.read-. I assumed it would be stored in the serial chip's memory and when full it would just drop new data. I'd make sense that, if an internal buffer expands with arriving data it would end up too big... I'll give that a shot and report back

Try hooking the ErrorReceived event on the SerialPort and see if that provides more information. If you are overflowing the internal buffer it will generate an exception with the event type of RXOver.

IMUSerial = new SerialPort("COM1", 9600, Parity.None, 8, StopBits.One);
IMUSerial.DataReceived += new SerialDataReceivedEventHandler(IMUSerial_DataReceived);
IMUSerial.Open();

//write IMU code
Debug.Print("Serial is " + (IMUSerial.IsOpen? "open" : "not opened"));
byte[] pip = System.Text.Encoding.UTF8.GetBytes("r");

Debug.GC(true);
while (true)
{
	IMUSerial.Write(pip, 0, 1);
	Thread.Sleep(100);
	
}

static void IMUSerial_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
	byte[] buffer = new byte[10];
	IMUSerial.Read(buffer, 0, 10);
	String message = new String(System.Text.Encoding.UTF8.GetChars(buffer));
	Debug.Print(message);
}

What happens if you move the buffer array up to the class level rather than creating a new instance each time the event fires?

I know this is an old thread but I came across it just now as I was trying to get RS232 up and running on my Netduino.

If you're looking for a really cheap board to do the conversion from TTL (3V) to RS232 you could try this one from Futurlec which is only $4.90 and is working fine with my Netduino.

- Adam

There doesn't seem to be support for multiple SPI devices on the same SPI interface in this framework.
It is possible to do your own CS (chip select) managing, but i prefer the way the SPI class manages this.
So i've made a little factory for making it easy to switch between spi devices.

The SPI class represents the master device (the Netduino).

Each slave device on the SPI bus is represented by a separate SPI.Configuration and since you can only have one active device at a time, you simply need to switch the configuration when you want to select a different device:

SPI.Configuration slaveDevice1 = new SPI.Configuration(Pins.GPIO_PIN_D10, false, 0, 0, true, true, 500, SPI_Devices.SPI1);
SPI.Configuration slaveDevice2 = new SPI.Configuration(Pins.GPIO_PIN_D9, false, 0, 0, true, true, 500, SPI_Devices.SPI1);

SPI spi = new SPI(slaveDevice1);

spi.Config = slaveDevice2;

I think that the NETMF terminology is a bit confusing in this regard. I would have preferred something like SPI.SlaveConfiguration which makes the relationship a bit clearer. It would also have been nice to have a Configuration collection within the SPI class itself.

- Adam

Anyone here have any experience with magnetometers?

Which one(s) have you used? What interface? How easy is it to work with? How well did the tilt-compensation (if any) work?

I'm not very experienced with them but I did just get one working with my Netduino so I thought I'd share that with you ;-)

I've had a Sure Electronics Dual-axis Magnetic Sensor Module (DC-SS503) sitting around for a while and wanted to experiment with the I²C interface. It turns out to be a really simple interface and I'd recommend it not just because it's simple but also because you can chain a bunch of I²C devices on a bus which avoids using all your Netduino pins driving multiple sensors.

Anyway, like I said, I'm not an expert but I hooked it up and got some data back which changes as I rotate the device in the X or Y axes. What that data means is my next task to figure out.

This is the test code I used to initiate a measurement and read the results:

byte[] buffer = new byte[5];
int bytesWritten = 0;

// Create the I2C device (device address: 0x30, clock rate: 400Khz)
I2CDevice.Configuration i2cConfig = new I2CDevice.Configuration(0x30, 400);
I2CDevice device = new I2CDevice(i2cConfig);

// Send command to take measurements (0x00) followed by (0x01)
I2CDevice.I2CTransaction[] writeTx = new I2CDevice.I2CTransaction[] { I2CDevice.CreateWriteTransaction(new byte[] { 0x00, 0x01 }) };
bytesWritten = device.Execute(writeTx, 1000);

// Pause for (minimum) 5ms as device completes data acquisition
Thread.Sleep(10);

// Read the 5-byte response from the device
I2CDevice.I2CTransaction[] readTx = new I2CDevice.I2CTransaction[] { I2CDevice.CreateReadTransaction(buffer) };
bytesWritten = device.Execute(readTx, 1000);

Debug.Print("Internal Register: " + buffer[0].ToString());
Debug.Print("X-Axis: " + ((buffer[1] * 0x100) + buffer[2]).ToString());
Debug.Print("Y-Axis: " + ((buffer[3] * 0x100) + buffer[4]).ToString());

Make sure you have the 4.1.1 ALPHA 7 firmware.

Hope that helps.

Ryan,

The code you posted to create the port should work. I tried it and it works for me - at least I was able to create the port and execute the DisableInterrupt call.

So it seems likely that some of your other code might be affecting this code. I would suggest much the same thing as vernarim: Take out as much other code as possible to prove that you can create the port and then gradually add back in the other code until you discover what's causing this code to break. Then, if the answer still isn't clear, you can post all the relevant code and get some more help.

- Adam