A pull-down resistor pulls the output to ground - so, there will be 0% PWM output (logic low) during Netduino startup (when the pin is floating high).

Your missing the point, 0% output is not logic low, 0% output is a pulse lasting 1000 microseconds every 20 milliseconds. Holding the pin low would not do anything.

I see - sorry for my misunderstanding.

No problem I didn't mean to be rude in my response. Actually thinking about it though it might be worth a try. I wasn't thinking about the fact that the pins will float during startup, I'm gonna try this anyways it might actually be a solution. Given not what I was thinking of, but I will report back if this works.

Cheers

The fist thing that jumps out is you specified address 2 and 3 in you post, but 0x29 in your code. If the address is supposed to be 2 then cahnge the first line to : I2CDevice i2c = new I2CDevice(new I2CDevice.Configuration(0x02, 100));

Any variable voltage (IE, not 3.3V OR 0V inclusive) needs to be measured through an analog pin. You may need to use a voltage divider to drop the voltage to a level between 0V and 3.3V. Look for a voltage divider calculator to find the correct values of the 2 resistors.

Please note, if you are tapping off a motor lead like that, you may need to use some form of circuit protection. Motors are noisy and may wreck havoc on the Netduino if the sampling circuit is not correctly done.

The netduino's MCU AT91SAM7X512 pins are 5V tolerant so even though they only output 3.3V they can handle up to 5V as an input, that being said I wouldn't let the netduino look at an inductive load like chris says. Your just asking for trouble. Instead I would recommend prying open the control board to look for a digital signal (5V or less) that represents the motor action. To do this you will need a multimeter, just trigger the motors and start probing around for the signal.

Cheers!

I've already touched on this. It can be used by pretty much any I2C device on probably any .NET Micro Framework device.

My work -> A derivative of Pavel Bansky's I2CBus class, but implements the singleton pattern (because it should be implementing the singleton pattern since you are supposed to only have one instance of the I2CDevice class.) You really might want to explore using the singleton pattern so that you guarantee that there is only one instance of the I2CDevice being used by your I2C devices.

I used this in the Bosch BMP085 Digital Pressure and Temperature Sensor

FYI my singleton implementation of the I2CBus class is being used in several projects with as many as four I2C devices on operating on the same bus.

phantom I just finished reworking my quad project to including your I2CBus, works fantastic! I really like this approach, elegant and simple.

Cheers!

Hi Luke,

I converted your code to a DLL, imported it into Visual Basic and it works like a charm. All other unsafe code I tried trashed my Netduino. Thanks for providing this badly needed functionality.

Baxter

Glad I could help. There definitely are some 'gotchas' using this technique.

Hi Luke,

I'm used to programming in C & C++

...

e.g. is is possible to prevent .Net making changes to the memory in the background during an unsafe function call?

Paul

Paul,

Pointers in C# using the unsafe construct are just as dangerous as in any other case. For example check out how I managed to brick my FEZ panda on this thread: http://www.tinyclr.com/forum/12/2700/. Using pointers gives you unfettered access to any memory you choose.

Really my mistake could have been made whether I was using managed or native code. Once you start getting into more advanced topics, like accessing various chip features (ie IAP on the NXP chip that GHI uses for USBizi) it becomes risky, especially when you know just enough to get yourself in trouble

edit:
@Mario: you are correct about it not being supported, but I've never had an issue using it. In this case my conversions were 3 times faster than anything else I could come up with.

-Luke

I would hate to drive traffic on a rival site so for fairness, here is the bitconverter class.

Just for sake of it, here is the code I was using for my quad copter project. Of all my testing this ended up being the fastest. http://code.tinyclr....4/bitconverter/

Move your _coefficients.Length statement to it's own local variable, before you loop and then reference that. It's much faster in netMF than referencing the property.

Also, underscores are against most best practices for .Net

Hey Mark, good catch i didn't even notice I did that. Also the _privateMember or m_privateMember is apart of most c# coding standards I've seen.

Brandon, I think you're reading my comments in the wrong tone - i meant them as a general comment, not targeted at anyone specific. I'm an Aussie, we're pretty layed back and chill - if in doubt, just read my post as a layed back view point

Please feel free to take a look at these links:
IDesign have an exceptional coding standard for C#, which a lot of companies I know of base their standards on. These are basically an expansion of Microsoft's:
http://www.idesign.n...ng Standard.zip - zip with PDF.


This is what Microsoft use internally: http://blogs.msdn.co.../26/361363.aspx

The guideline for creating class libraries is a rather informative read: http://msdn.microsof...y/ms229042.aspx

And this is the book I mentioned (which I recommend every developer - professional, amatuer and enthisuast alike read) - http://www.amazon.com/dp/0321545613/ - on on Book Depository if you're not in the USA (free shipping! woo) http://www.bookdepos...sign-Guidelines

IDesigns C# standards (my personal favourite), section 1 point 4:

Prefix member variables with m_. Use Pascal casing for the rest of a member
variable name following the m_.

public class SomeClass
{
   private int m_Number;
}

If you are at all concerned with speed and/or the gc, you should try my approach:

When dealing with bit conversions always use the Utility class, for instance working with floats:

public static unsafe float ToFloat(ref byte[] buffer, int offset)
{
   uint value = Utility.ExtractValueFromArray(buffer, offset, 4);
   return *((float*) &value);
}
public static unsafe void ToBytes(ref byte[] buffer, int offset, float value)
{
   Utility.InsertValueIntoArray(buffer, offset, 4, *((uint*) &value));
}

Note that the name ToBytes isn't exactly accurate as normally a bit converter would return the array, but usually you are using this to pack data in a long buffer, and using the reference saves the additional hit for making a new array.

or how about a double word sized variable:

public static long ToLong(ref byte[] buffer, int offset)
{
   long value = (long)Utility.ExtractValueFromArray(buffer, offset, 4) << 32;
   value |= Utility.ExtractValueFromArray(buffer, offset + 4, 4);
   return value;
}
public static void ToBytes(ref byte[] buffer, int offset, long value)
{
   Utility.InsertValueIntoArray(buffer, offset, 4, (uint)(value >> 32));
   Utility.InsertValueIntoArray(buffer, offset + 4, 4, (uint)value);
}

Obviously you could adapt this for any other types you require. These are just what I use in my current project.

Cheers

Hi guys,

I am looking for a ATmega 328p programmer. The reason is that my 9dof from Sparkfun has (apparently - what a bummer) a flawed bootloaded and needs to be reflashed.
Thus I am wondering if you have any recommendations (possibly being available in EU).

I guess I'll have to solder SPI pins as well. Just great

If you already have a spare arduino you can reflash the arduino bootloader like this:
http://arduino.cc/en...rial/ArduinoISP