myRIO i2c probelm

[RokCapuder]

Hi I've just started using the myRIO. I'm using the I2C to connect a remote device (motor controller). I figured out how to send data (speed), but Im having problems reading some values with the I2C function of myRIO. I want to read the register at 0x11 of my device. How can I specify which register I want to read? Thanks.

[MrHappyAsthma]

I can't speak specifically to the myRIO, but for I2C in general, you will send the following (Note:  Bold items are responses from the slave, the normal font are the bits you transmit):

Start Bit -> Slave Address (Write) -> Slack Ack -> Register Address (0x11 in your case) -> Slave Ack -> Repeat Start -> Slave Address (Read) -> Slave Ack -> [Read Data (8 bits) -> Master Nack]

To do a repeated read (if your device supports it), the bracketed segment gets replaced with:

[Read Data (8 bits) -> Master Ack -> Read Data (8 bits) -> Master Ack .... Read Data (8 bits) -> Master Nack]

If you have a more specific LabVIEW I2C related question, post the code you have so far and I can take a look at it.

[RokCapuder]

Thanks for the fast reply HappyAsthma !

Below is the VI i'm sing and its not working in the current state. Should I wait for some time between the write and read event?

[MrHappyAsthma · Accepted solution]

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@RokCapuder wrote:

Thanks for the fast reply HappyAsthma !

Below is the VI i'm sing and its not working in the current state. Should I wait for some time between the write and read event?

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No.  You should not need to wait (the exception being if you were manually manipulating the clock).  Per specification, you send a bit every clock cycle.

And I cannot open the VIs specifically since I don't have the library/drivers installed, but try using the Write Read VI to do your reads instead of manually doing 1 write and then 1 read:

http://zone.ni.com/reference/en-XX/help/373925A-01/myrioreference/myrioref_i2cwriteread/

You should send the Slave Address, Bytes To Write == 0x11, Byte Count = number of bytes you want read (your device may need a special value to be set in a register to do incremental "burst reads")

EDIT:

My guess (without seeing the VI code) is that the Write VI and Read VI are sending the STOP bit automatically once they are done writing/reading all bytes.  The Write Read VI is likely configured to Write the byte(s) and then immedately Read some byte(s) before sending the STOP bit.

[RokCapuder]

Aaaaah I get it now! So simple 🙂

Thank you HappyAsthma!

[MrHappyAsthma]

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@RokCapuder wrote:

Aaaaah I get it now! So simple 🙂

Thank you HappyAsthma!

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Glad to hear it!  😄

Don't forget to mark the solution!

[vamshikrishna]

Is there any NI modules which contains analog measurements and digital measurements and frequency and also main I2C communication in one module???

Please give a suggesion if any third party modules also including above parameters.

[GerdW]

duplicate post, continued here!

[shreya111]

Sir,

     I have to control the motion of 4 DC rhino Servomotors using Spartan 3E board.I have to implement through I2C communication.I have made a VI for controlling a single motor.steps that I have followed are-

1.I have used the J1 header pins I/O1 and I/O2 as SCL and SDA pins respectively.

2.In the VI, initially both SCL and SDA lines are high.

3.while the scl is high ,sda makes a transition from high to low.

4.after that I have set the SCL line low to send the address and the data byte on the SDA line.After the communication is over , again both the lines become high.

Problems:

1.While sending the data through the VI to vary the speed of the motor ,its not varying."

2.the motor is not stopping upon sending data 0 .

3. I have to control the motion of 4 motors at a time.I am facing problem as to how to address them and what all changes I need to make in the VI.

Please provide me the valuable suggestions and modification needed in the VI as soon as possible.

Thanking You,

Regards

Pooja

[natasftw]

Just because you bumped several old threads related to i2c doesn't mean we're willing to do your homework for you.

Start a new thread.  Tell us what you've done.  Tell us where you're stuck.  Ask for help.  Do NOT ask us to do your work for you.