10 replies to this topic

[tax]

Hi Guys, I need to pickup data from a I2C device vith the Netduino as Master. I cant seem to find any examples. Do you know any or could you give me a pointer on where to start? Im pretty new in this .NET micro framework, so Im suer im making all the Noob mistakes. I have found snippets online, but I have not been able to use them due to missing includes. Kind regards Tax

[phantomtypist]

Take a look at my code for the I2CBus implemented in the singleton pattern (because you can only have one instance of I2CDevice)

After that, take a look at a driver I wrote for the Bosch BMP085 temperature and pressure sensor.

[Chris Walker]

Im pretty new in this .NET micro framework, so Im suer im making all the Noob mistakes. I have found snippets online, but I have not been able to use them due to missing includes.

Hi Tax,

Welcome to the Netduino community.

If you can share the code snippets you're trying and the errors you're getting (missing includes/references), I'm sure somebody would be happy to help point you in the right direction...

Chris

[Ryan Mick]

It would be nice if there was a beginners tutorial on using I2C with the Netduino. Not just the code but connecting multiple devices to the bus. I know your suppose to use pull up resistors but I can't find any information on when to use them what type or how often. But a short and sweet tutorial would be great to answer these type of question us beginners have. And it would have the added benefit of being easily found.

[Michel Trahan]

It would be nice if there was a beginners tutorial on using I2C with the Netduino. Not just the code but connecting multiple devices to the bus. I know your suppose to use pull up resistors but I can't find any information on when to use them what type or how often. But a short and sweet tutorial would be great to answer these type of question us beginners have. And it would have the added benefit of being easily found.

I agree ! Beginners Tutorial Please

[CW2]

I know your suppose to use pull up resistors but I can't find any information on when to use them what type or how often.

There need to be two pull-up resistors connected between I2C signal lines (TWCK, TWD) and positive voltage (+5V or +3.3V depending on the devices connected). The value can vary from ~1.5 kΩ up to ~47 kΩ, 2.2 kΩ or 10 kΩ will work fine. The exact value would have to be calculated based on the bus characteristics, i.e. capacitance, number of devices connected, speed etc.

[Michel Trahan]

There need to be two pull-up resistors connected between I2C signal lines (TWCK, TWD) and positive voltage (+5V or +3.3V depending on the devices connected). The value can vary from ~1.5 kΩ up to ~47 kΩ, 2.2 kΩ or 10 kΩ will work fine. The exact value would have to be calculated based on the bus characteristics, i.e. capacitance, number of devices connected, speed etc.

And if I see only SCL and SDA ... no TWCK nor TWD ... This is why we need a tutorial ... with some diagram using a netduino and some sensors (ex: Accelerometer ADXL345, Magnetometer HMC5843 and Gyroscope ITG3200). Real example with real sensors ...

I do understand that hardware is hard (pun intended) ... please help the newbies like me with some tutorials with real things connected, not just LEDs I am willing to help but I need input ... hard input !

Mike who wants to play with sensors without burning them !

[CW2]

And if I see only SCL and SDA ... no TWCK nor TWD ...

I²C Clock = SCL = TWCK
I²C Data = SDA = TWD

'TW' is used in Netduino schematic and Fritzing parts, because it is based on Atmel microcontroller and Atmel calls its I²C implementation "Two-Wire Interface", TWI for short. Sorry for the confusion.

[Michel Trahan]

Sorry for the confusion.

LOL It made my point clear though ! LOL

Did I understand correctly, you ALWAYS need pullup resistors ? or only when there is more than one sensor connected to it ? And using a I2CBus class to encapsulate all this would be nice to have (to clean up the code) ?

[CW2]

Did I understand correctly, you ALWAYS need pullup resistors ?

Yes - technically, you'd need to ensure the I²C signal lines are HIGH, when the bus is free - you can use either a current source or pull-up resistor connected to the positive supply voltage. Pull-up resistors are "easier".

or only when there is more than one sensor connected to it ?

The pull-up resistors should be present always. However, some sensors/devices may have those built-in (e.g. Sparkfun breakout boards).

And using a I2CBus class to encapsulate all this would be nice to have (to clean up the code) ?

I am not sure I understand that - what do you mean by 'encapsulate all this'? As far as I know I2CBus class is used to overcome limitation in the current .NET Micro Framework I²C implementation that does not directly support multiple devices on the same bus (i.e. it is not possible to instantiate second I2CDevice, because it tries to reserve pins that have been already exclusively reserved by the first instance).

[Michel Trahan]

However, some sensors/devices may have those built-in (e.g. Sparkfun breakout boards).

Boy do we need a tutorial LOL

what do you mean by 'encapsulate all this'?

Sorry, my lack of knowledge ... I didn't know why it was created ! Thanks !