I am having an issue where I am getting duplictate/inserted data points when sampling from the ADS1259. As a test I set up a GPIO line on my processor to output high when two sequential readings are equal and low when they are different. I then used that as a trigger on my scope to see what the DRDY line is doing when a duplicate sample is detected. As you can see below (top signal is the GPIO line, bottom is DRDY), sometimes DRDY does not return high when clocking out data. Since my code initiates sampling when it detects that DRDY is low, I am obtaining the same data point twice. Do you have any idea what may be causing this issue and how I may resolve it?
When reading conversion results from the ADS1259 on the RDATAC mode, the user must monitor the Falling edge of the DRDY signal. Typically the processor would be set up in a routine with an interrupt that detects the falling-edge of DRDY to read the conversion data. When using the device on RDATAC mode, the data read operation must be complete 20flck cycles before of the next DRDY cycles; before the update of the output register with new conversion results occur. The same conversion data could be read again by continuing to shift data; Notice, it is not sufficient to detect when DRDY is low, but to detect the falling edge of DRDY to read the data.
What kind of signal is being fed to the ADS1259?
For the specific test I was running when I generated that screen shot, the ADS1259 was being given a 1KHz 20mVpp sine wave offset +15mV.
I will likely implement an interrupt routine for this purpose, however, I that still leaves the question of why the DRDY line is behaving as it is. According to the figure you attached, note 1 specifies that DRDY should return high on the first falling edge of SCLK. However, in some instances DRDY does not return high until at least the start of the second full read operation (on the 25th falling edge).
Were you able to resolve your issue? Usually these types of issues are related to timing.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.