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AD7195 unable to rail?

Question asked by cydrollinger on Feb 20, 2015
Latest reply on Feb 26, 2015 by cydrollinger

The AD7195 within the system has been initialized: 48 1's written to the device, the configuration has been written with 0x000347, and the mode has been written with 0x180060. Purposefully setting the device to read two channels with bipolar, 128 gain, ref_det, data+sta, and 50Hz. An attempt at system calibration, first zero and then full before making measurements with again writing 0x180060 to the mode register.

Question: This gain setting forces the differential input signal range to +-40mV before railing the data conversion to either 0x000000 or 0xFFFFFF, but the AD7195 does not output these values no matter the value of the differential input value, even to a couple of volts. What's that about?

The GPOCON register always reads 0x06 even after attempting to write 0x00. The datasheet expresses that the two bits in 0x06 need to be 0 and 0? Related or not?


Thank you for considering my problem,