I'm not 100% sure, but I think this is not supported. I think you'll have to tie two pins together, configuring one as a TriStatePort and the other as an InterruptPort. You'll (hopefully) see two pulses on the InterruptPort: your own outgoing pulse and then later the reply from the PING)))

Hey Corey,

That's what I was thinking too but I was hoping it wouldn't be the case - it seems like a waste of resources to use two pins.

I don't understand why there's an OnInterrupt event on the TristatePort if you can't use it. It makes sense that event wouldn't fire unless the port was set for input but it seems I can't hook the event at all.

The obvious option is to abandon interrupts and just go with the TristatePort for everything but an interrupt seems tailor-made for this type of operation...

- Adam

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 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.

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

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 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

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]}

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]}

I'm just starting to think about powering my projects from batteries.

I got this 2000mAh Polymer Lithium Ion Battery and this converter so I think I have the Netduino and sensors covered but I'm wondering about devices, such as motors, that require a bit more power.

I know there are a ton of options out there but I wanted to find out what people here are using and what works well.

Thanks in advance.

- Adam

I use RC grade Lipos/NiMhs.

Check this sorta stuff out: http://www.hobbyking...?idProduct=8935

Thanks Chris.

Looks like a good way to go.

Confirmed. I see the same behaviour in NETMF but not in the full framework. -0.1 to -0.9 are parsed as positive values.

Interesting video. Given that the Compact Framework only implements one-generation GC, I wouldn't imagine that the Micro Framework is any different. Which leads to an equally interesting observation: In a one-generation GC, every live object on the heap must be considered during each garbage collection. Therefore, the more long-term objects in a NETMF application, the slower the GC cycle. Reducing the number of long-term objects should improve overall GC performance. If correct, that observation will certainly have a bearing on the way I code my NETMF apps. - Adam

The garbage collector in .NET Micro Framework is a simple mark-and-sweep.

So do you think that it is a good strategy to avoid long-term objects as much as possible in NETMF code?

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

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.

I have used the i2cmaster.h when i was working with arduino. Now i try to convert it to C# but i dont understand it.
Can some pleas help me convert this code to c#.

Having just figured out I²C myself, I can tell you that you don't have the same (low) level of control over I²C in C# (NETMF). The I2CTransaction wraps the complexities of the protocol and handles the start/stop/acks for you.

Here's some basic test code that I used to read/write a 24LC32A serial EEPROM:

public static void Main()
{
	byte[] buffer = new byte[1];
	int bytesWritten = 0;

	// Create the I2C device (device address: 0x54, clock rate: 50Khz)
	I2CDevice.Configuration i2cConfig = new I2CDevice.Configuration(0x54, 50);
	I2CDevice eeprom = new I2CDevice(i2cConfig);
			
	// Write the letter 'A' (0x41) to address 0x0000 on the eeprom
	I2CDevice.I2CTransaction[] writeTx = new I2CDevice.I2CTransaction[] { CreateWriteTransaction(new byte[] { 0x00, 0x00, 0x41 }, 0, 0) };
	bytesWritten = eeprom.Execute(writeTx, 1000);

	// Read the byte at address 0x0000 on the eeprom
	I2CDevice.I2CTransaction[]  readTx = new I2CDevice.I2CTransaction[] { CreateReadTransaction(buffer, 0x0000, 2) };
	do { bytesWritten = eeprom.Execute(readTx, 1000); } while (bytesWritten == 0);

	Debug.Print(buffer[0].ToString());

	Thread.Sleep(Timeout.Infinite);
}

#region see: http://forums.netduino.com/index.php?/topic/944-i2c-internaladdress-repeated-start-bit-support/

static I2CDevice.I2CWriteTransaction CreateWriteTransaction(byte[] buffer, uint internalAddress, byte internalAddressSize)
{
	I2CDevice.I2CWriteTransaction writeTransaction = I2CDevice.CreateWriteTransaction(buffer);
	Type writeTransactionType = typeof(I2CDevice.I2CWriteTransaction);

	FieldInfo fieldInfo = writeTransactionType.GetField("Custom_InternalAddress", BindingFlags.NonPublic | BindingFlags.Instance);
	fieldInfo.SetValue(writeTransaction, internalAddress);

	fieldInfo = writeTransactionType.GetField("Custom_InternalAddressSize", BindingFlags.NonPublic | BindingFlags.Instance);
	fieldInfo.SetValue(writeTransaction, internalAddressSize);

	return writeTransaction;
}

static I2CDevice.I2CReadTransaction CreateReadTransaction(byte[] buffer, uint internalAddress, byte internalAddressSize)
{
	I2CDevice.I2CReadTransaction readTransaction = I2CDevice.CreateReadTransaction(buffer);
	Type readTransactionType = typeof(I2CDevice.I2CReadTransaction);

	FieldInfo fieldInfo = readTransactionType.GetField("Custom_InternalAddress", BindingFlags.NonPublic | BindingFlags.Instance);
	fieldInfo.SetValue(readTransaction, internalAddress);

	fieldInfo = readTransactionType.GetField("Custom_InternalAddressSize", BindingFlags.NonPublic | BindingFlags.Instance);
	fieldInfo.SetValue(readTransaction, internalAddressSize);

	return readTransaction;
}

#endregion

Make sure you have the 4.1.1 ALPHA 7 firmware.

Hope that helps.