ads1298 wrong samples

Hi Maximiliano!

Welcome to our forum!  This looks like there might be an error in your SPI communication setup with the ADS1298.  Can you post any screen shots from an oscilloscope that shows your SDCLK, SDI and SDO?  Is this your own hardware that you've built or are you trying to wire your controller into the ADS1298ECGFE-PDK hardware?

Hi Tom, thanks for answering so quickly

I have built two different circuits, both with the same microcontrolker and spi rutines.

 I would like to give you those screen shots, but since only have a two channel oscilloscope, i will show you only SDI (MISO) and SDCLK. However SDO is always on a low level because my dummy data to read the ads1298 is always 0x00;

 the yellow signal is the sdclk and the red one is the SDI.

These capture is taken when a data ready is read. they correspond to the status and channel0 signal. i dont understand why there is a pulse in SDI before the first SDCLKs 

 Thanks in advance for your help

Hi fellows, I'm Marcos, and I'm working with Maximiliano in this project.

Note the shape of the waveform shown in the first post. It looks like there are 10 signals mixed up. I saw another acquisition when it looks like there were 4 signals: 2 sines and 2 dc (almost zero), interleaved in the same way [sine1, sine2, dc1, 0,sine1, sine2, dc1, 0,...], and the original injected signal was a 4Hz sine.

Also, we just found the SDO pulse in the datasheet, its equivalent to the DRDY, in order to save the DRDY connection to the MCU. 

Unfortunately, I blew the MCU because of a power supply failure; I was trying to see if the MISO data was steady enough (I was applying a constant voltage to the ADC).

I guess we'll come back in a couple of days, when I fix the damaged components of the board.

Best regards

Hi Max and Marcos,

How are you making out here?  Have you resolved your issues?

Hey marcos and Maxi, my name is Alberto. I'm also from Argentina and I think that i have the same problem as you with a sin waveform of 10Hz. For example, here is a picture from matlab:

I made a previous post with where I described in which way I worked to get that signal.

http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/t/207376.aspx

Do you think that this is because of some problem in the spi interface? With a DC input I had no problem that's why i thought that the connection couldent be. But I've no idea what happens.

Thanks for your time. Regards,

Alberto

Hi Tom

We are still facing problems, no we think that most of them are because ofelectronic noise. I would appreciate any recommendation you could give me.

It would be nice to  see examples of using this IC besides the development kits.

Regards

Maximiliano

Maximiliano Cordoba

It would be nice to  see examples of using this IC besides the development kits.

Here is an project with the ADS1298:

http://code.google.com/p/opendous/wiki/BioSensorPlatform