ADS7854 Problem

Hello Pablo,

Welcome to the e2e forums.

Could you please confirm whether oscilloscope channel 3 corresponds to SDI, SDO-A or SDO-B? My assumption is that channel 1 is the ~CS line and that channel 2 is the SCLK line, could you please confirm that as well?

The best way to troubleshoot the problem would be to observe at least ~CS, SCLK, SDI and SDO-A all at once and for two consecutive frames.

If channel 3 corresponds to SDI, then it seems to me that the screen capture corresponds to a command where you instruct the ADS7854 to put the serial interface in 32-CLK mode, use only SDO_A to put out data, put the input range as +/- VREF and use the internal reference.

Best regards,

Jose

Hello Pablo,

The following sentence from your previous post is key “I'm trying to configure the device as before, but after that I try to read configuratio nregister.”

If you were successful in setting the ADS7854 serial interface in 32-CLK mode and use only SDO_A to put out data, then you MUST issue at least 48 SCLK cycles to when reading and writing data. It seems to me that your read operation only contains 32 SCLK cycles.

Two important points:

1)      Make sure the ADS7854 serial interface is in 32-CLK, dual-SDO mode before you issue the configuration command shown on your Oct. 9^th post.

2)      Make sure you abide by the Serial Interface Timing Diagram (figure 1) of the ADS7854 datasheet.

My suggestions would be to thoroughly review section 8.5 (pages 33 to 46) of the ADS7854 datasheet.

With regard to potential hardware issues:

If the ideas above do not solve the issue, then it would be good to disconnect SDO_A from the SPIA line in your microcontroller just in case the micro is keeping SDO_A low. Probe with the oscilloscope (on SDO_A) after disconnecting SDO_A and see if you observe the proper data.

Hope this helps.

Best regards,

Jose