ST95HF datasheet(65/93 Pages) STMICROELECTRONICS

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ST95HF

Example of tag detection calibration process

Appendix B

Example of tag detection calibration process

The following script works on the DEMO_CR95HF evaluation board and with the ST95HF

development software available on www.st.com.

This is a dichotomous approach to quickly converge to the DacDataRef value for which a

wake-up event switches from tag detection to Timeout. In this process, only the DacDataH

parameter is changed in successive Idle commands. And we look at the wake-up event

reply to decide the next step.

00 01 02 corresponds to a Tag Detect,

00 01 01 corresponds to a Timeout.

REM, Tag Detection Calibration Test

REM,

Sequence: Power-up Tag Detect Wake-up by Tag Detect (1 try

measurement greater or equal to DacDataH) or Timeout

REM,

CMD 07 0E 03 A100 D801 1800 01 60 60 00 XX 3F 00

REM,

WU source = Tagdet or Timeout

REM,

A100

Initial Dac Compare

REM,

F801

Initial Dac Compare

REM,

1800

HFO

REM,

20 Wup Period 32 Inactivity period = 256ms (LFO @ 32kHz)

REM,

60 Osc

3ms

(LFO @ 32kHz)

REM,

60 Dac

3ms

(LFO @ 32kHz)

REM,

DacDataL

= minimum level (floor)

REM,

DacDataH 00 = minimum level (ceiling)

REM,

Swing 13.56

4.6 us

REM,

01 Maximum number of Sleep before Wakeup 2

REM, Tag Detection Calibration Test

REM, During tag detection calibration process DacDataL = 0x00

REM, We execute several tag detection commands with different

DacDataH values to determine DacDataRef level corresponding to

ST95HF application set-up

REM, DacDataReg value corresponds to DacDataH value for which Wake-

up event switches from Timeout (0x01) to Tag Detect (0x02)

REM, Wake-up event

= Timeout

when

DacDataRef is between DacDataL

and DacDataH

REM, Search DacDataref value corresponding to value of DacDataH for

which Wake-up event switches from Tag Detect (02) to Timeout(01)

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