Problem in Tag Calibration of CR95HF

jane · ‎2014-08-22

Posted on August 22, 2014 at 23:45

I have been working with the CR95HF chip for about the last month. I need to be able to use the Tag Detect version of the Idle state for my application. However, when I attempt to run the Tag Calibration sequence, I get a Wake Up response of 0x02 (value of the third byte) during the second step when my DACDataH value is 0xFC, which according to the Application Note, AN3433, is an error state. I would assume it was a problem with my matching network or with my receive pins, but the other RF operations I am interested in (inventories, reads and writes) are functional.

I have tried changing the value of the Rrx resistors (from 330 ohm to 249 ohm), but if i lower the value, I encounter the opposite problem: I only get a Wake Up response of 0x01 until my value of DACDataH is 0x03 while attempting to calibration and this value clearly doesn't lead to a usable DACDataL value for actual Idle commands.

Has anyone else experienced this problem or know a possible cause/solution?

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elliott · ‎2018-07-03

Posted on July 03, 2018 at 18:47

Peter,

Thanks for the response. I think I've found the issue - we had a version

of hardware that didn't have IRQ_IN connected to the host MCU. Once I

switched to our corrected hardware, this issue was resolved.

Thanks very much,

Elliott

On Mon, Jul 2, 2018 at 10:48 AM Peter Boringer <

View solution in original post

elliott · ‎2018-06-19

Posted on June 19, 2018 at 22:44

I have encountered this issue as well. However in my case, I am unable to communicate with a tag at all, regardless of whether calibration is performed or not. But performing calibration always returns the 00 01 02 response (Wake up tag source).

I realize this is 4 years old, but do the mods have any response? Here is a trace of my communication:

nfctx: 00 07 0e 03 a1 00 f8 01 18 00 20 60 60 00 00 3f 01

nfcrx: 00 01 02

nfctx: 00 07 0e 03 a1 00 f8 01 18 00 20 60 60 00 fc 3f 01

nfcrx: 00 01 02

Peter Boringer · ‎2018-07-02

Posted on July 02, 2018 at 16:48

Hello Elliot,

With so few information it can be difficult to help you.

Anyway, If I understand well,

1)you have not be able to get any answer from a TAG

2)You try to calibrate the TAG detection unsuccessfully

Let me suggest 1st can you provide your antenna circuitry (antenna impedance and matching circuit used)

At the same time you can measure with an active probe (low input capacitor) the voltage at the input RX on the CR95HF this level should be lower than 8 Volts in single ended. I suspect that the input circuitry receive a too high signal that prevent the receiver and also the comparator used to calibrate the DAC to work properly.

You can also experiment by trying the same DAC calibration but with a TAG tightly coupled to the antenna this might detune the reader and thus the cal procedure might works (performing an idle command as described in you mail with 1st a DACH = 0 then the same command DACH = FC) in that case the answer could be 0101.

Hope it will help

Regards

PB

elliott · ‎2018-07-03