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CR95HF Calibration Issue

Question asked by joseph.geethu on Jun 19, 2014
Latest reply on Aug 28, 2014 by ST NFC

I have two applications one for the Calibration of CR95HF and one for Tag detection. Before running the Tag detection application Calibration is done and the DAC ref value obtained is saved in a file. The Tag detection application uses the DAC ref value and puts the CR95HF device into IDLE mode with the wakeup event configured as Tag Detection. When a TAG is placed in the proximity area, device wakes up and the application reads the UID. Most of the time everything is working fine. But sometimes, the device is not waking up from IDLE mode, even if TAG is placed in the vicinity area. It may work after some time after some board resets and all. I couldnt find the issue as its not coming regularly. But the issue is a repeating one. 

One thing I observed is I am getting different DAC Ref value for the same board with antenna connected and without antenna connected. say 0x03 and 0x07. What is the part that antenna does during the calibration procedure.?

Also when the Tag detetion application fails, I have seen that the DAC Ref value obtained is the value without antenna, ie 0x03. And When the Tag detection is successful, the Ref value obtained is 0x07. 

Please help me in finding the issue. 

Thanks in advance