I2C problem between the NXT and a Maxim ADC

[kosenhitatchi]

Hi everyone.



I'm using LabView 2009 service pack 1 an a NXT firmware 1.28 .



My goal is to command an ADC "MAX 127" from Maxim through a NXT. The DAC is connected to the NXT by the sensor plug port.



Here the doc :

http://datasheets.maxim-ic.com/en/ds/MAX127-MAX128B.pdf



I got some problems. I can not discuss with the DAC, with the NXT module "i2c communication".

I don't see any digital signal on the oscilloscope.



Could you help me to fix it.



Sincerly

[mightor]

Did you add 82k Pull-up resistors to your circuit?

- Xander

[kosenhitatchi]

Yes, I add two 82K Pull-up resistors to my circuit. One between SDA=>Vcc, the Other SCL => Vcc.

[mightor]

You tested your circuit with NXC or something to that effect?

- Xander

[kosenhitatchi]

I test my system with a NI-Elvis from National Instrument. A the begining I tried to visualise the Data transfer on the I2C Bus.

[mightor]

I'm sorry but I am not familiar with LV, perhaps someone else can help you.

- Xander

[kosenhitatchi]

I don't think that the problem come from the electric assembly.

Here it is :

[mightor]

Your circuit (the MAX127 part of it anyway) should look like in these posts:

• http://mightor.wordpress.com/2009/03/02 ... mux-board/
• http://mightor.wordpress.com/2008/07/27 ... he-max127/
• http://mightor.wordpress.com/2008/07/19 ... onversion/

If it doesn't then you need to go back to the drawing board.

- Xander

[philoo]

According to your schematics, your problem is that ground connection between NXT and converter is missing!

[kosenhitatchi]

Corrected