itg3200 i2c problem

Tom1234 · Joined: 06 Jan 2013 Posts: 39

Hello guys,

I am trying to program Itg3200 sensor module. I used the scanner program (http://www.ccsinfo.com/forum/viewtopic.php?t=47707&start=21 )

The problem is : when I used 1,5K or 1K pull-up resistor I see only 00 at the first case and regular counting (00,02,04,06….) At the second case.

What is going wrong . From the manual I can't find the right value for the pull-up resistor. Also I don’t know if the program at the above link is working right?

It will be helpful if someone has any idea.

Ttelmah · Joined: 11 Mar 2010 Posts: 19358

You need to tell us a lot more.

Yes, the I2C scanner works.

What PIC?.
What complier version?.
What supply voltage?.
What pins on the PIC?.

The Itg3200, is a 3.3v device. It won't directly drive the hardware I2C input on a 5v PIC. You can use it on some PIC's/pins, by running using software I2C. With a 3.3v PIC, it should work.

I2C bus pullup's depend on the length of the bus (capacitance), supply voltage, ratings of the device, and speed.
The output of the Itg3200 is designed for 3mA sink current, so 1KR, is going to be pushing it with 3.3v on the pullup's. If you have the pullup's going to 5v, then you are outside the specifications of the chip.
Something around 3.3KR, should be adequate provided your bus is not long.

I suspect your problem is voltage translation between the device voltages.

Tom1234 · Joined: 06 Jan 2013 Posts: 39

dspic33fj64GP202

Supply voltage =3.3V --> 1 k resistor is right

I2C pins : B8-->SCL1,B9-->SDA1

From the scanner program i expect to see only one value(address). Is this right???

dyeatman · Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK

What is VLogic pin 8 tied to?
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Tom1234 · Joined: 06 Jan 2013 Posts: 39

I didn't connect anything to VLogic pin

dyeatman · Joined: 06 Sep 2003 Posts: 1924 Location: Norman, OK

The datasheet says the VLogic pin voltage determines the I2C
bus signal levels. I would tie it to your 3.3V VDD to be safe.

Also, where are you reading that 1K pullups are the right value?
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Ttelmah · Joined: 11 Mar 2010 Posts: 19358

I suspect he may be finding a reference to this, which will list it as the _,minimum_ value. However provided the bus is not too long, something between 2.2K, and 3.3K, is a much better range for 3.3v I2C.

Vlogic is vital. I suspect this is the main problem. The chip will not respond properly to I2C without it.

Best Wishes

Tom1234 · Joined: 06 Jan 2013 Posts: 39

I used a 3 K resistors as pull-up resistors and also I connected
the Vlogic to VDD .

when I run the scanner program I receive only the value 00.
What is going wrong?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Did you buy the Itg3200 board or did you build it yourself ? If you bought
the board, post a link to the website for the board, so that we can see a
schematic for it. If you built the board yourself, then upload the
schematic to a free image hosting website, then post a link to it.

Also, post the #use i2c() statement that you are using.

Tom1234 · Joined: 06 Jan 2013 Posts: 39

I bought the sensor from the ebay (i asked the seller for the schematic).

For the i2c i used :
#use i2c(Master, sda=PIN_B9, scl=PIN_B8)

Tom1234 · Joined: 06 Jan 2013 Posts: 39

Guys I need your suggestions .what i need to do?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Post a link to the Ebay page so we can at least look at the board.

Tom1234 · Joined: 06 Jan 2013 Posts: 39

Sensor:

http://www.ebay.com/itm/260778520666?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I am searching for a schematic for that board.

But, by looking at the image of the board with the Invensense pin
diagram, I can see a few things:

This board has built-in i2c pull-up resistors, R1 and R2. The photo
is at an angle so it's hard to read the resistor value. But it looks like 332,
which is 3.3K, which makes sense for an i2c board running at +3.3v.
This means you don't have to add external pull-up resistors.

There is no documentation of the board's pinout. Did you get a sheet
of paper with the board that lists the functions of pins 1 to 7 ?
Or does the board have the pin labels printed on the back of the board ?
(example: VDD, SDA, SCL, for all 7 pins). If it does, then post it here.
Or make a photo of the back side of the board, upload it to a free image
hosting website and post a link to it.
Also, are there any components on the back side of the board ?

Here is my estimate of the board pinout:

1 - ?
2 - Vlogic
3 - Ground (probably)
4 - Vdd (probably)
5 - CLKIN
6 - SDA
7 - SCL

There are three gold pads at the bottom of the board. The center pad
is connected to the AD0 pin on the itg3200 chip. It appears from the
photo, that there is a trace going from the center pad to what is probably
the ground plane. Can you check that with an ohmmeter ? I want to
know if the AD0 pin is floating, or is it connected to ground (or possibly Vdd).

Tom1234 · Joined: 06 Jan 2013 Posts: 39

There is not any component on the back side of the board.

The pins label are printed (on the back side)are :
1)Vdd
2)Vlogic
3)GND
4)INT
5)CLK
6)SDA
7)SCL

I checked the 3 pads (with the pins) the first is connected to VDD and the last to the GND. The center pad is not connected

If you need any other information let me know.