AN3433 datasheet(27/34 Pages) STMICROELECTRONICS

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AN3433

Tag Detection Calibration process

Doc ID 019046 Rev 2

27/34

During the calibration process, DacDataL is set to

0x00 and the reference level is

determined changing only the DacDataH parameter.

The reference level corresponds to the switching level between wakeup sources. It is

determined using the fast dichotomist process in 8 steps;

The Tag Detection Calibration command is formatted as follows:

TagCal (Ref_H) =

0x07 0E 03 A1 00 F8 01 18 00 20 60 60 00 Ref_H 3F 01

All the parameters are predefined to fit applicative requests in terms of wakeup sources and

power consumption. A compromise must be established between the detection period and

power consumption.

TagDet (64,74, or DacDataL and DacDataH, respectively) is defined using the command:

>>> 0x07 0E 0B 21 00 79 01 18 00 20 60 60 64 74 3F 00

B.2

Tag Detection calibration command

The Tag Detection Calibration command (TagCal) is a special setting of the Tag Detection

command (TagDet) for which the only variable is Ref_H.

>>> 0x07 0E 03 A1 00 F8 01 18 00 01 60 60 00 XX 3F 00

<<< 0x00 01 01 (in the event of a timeout)

<<< 0x00 01 02 (in the event of a tag detection in the RF field)

Here, the third byte (the

WakeUp_n variable) defines the Wakeup event.

It is also possible to directly use the Wakeup Flag command:

0x08 03 62 01 00

Read Wakeup Flag reply:

–

In case of timeout:

0x00 01 01 (WakeUp_n = 0x01)

–

In case of Tag Detection:

0x00 01 02 (WakeUp_n = 0x02)

In Figure 11, the function TagCal (

0xRef_n) corresponds to the execution of the following

device Idle command:

>>> 0x07 0E 03 A1 00 F8 01 18 00 20 60 60 00 0xRef_n 3F 01

<<< 0x00 01 01 (in the event of a timeout)

<<< 0x00 01 02 (in the event of a tag detection in the RF field)

Here, the third byte (the

WakeUp_n variable) defines the Wakeup event.

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