Auto Antenna tuning in poling

[Mtaka.8]

I evaluate ST25R3916 by using ST25R3916-DISCO kit and STSW-ST25R010.

In Antenna features tab, I confirmed AAT_A and AAT_B values changed for tuning when a piece of metal is approached to the  antenna​, but in poling tab, these value did not change when the metal piece is approached. Is this correct operation? I think the antenna is continuously tuned in poling mode. If it is wrong, please tell me when auto antenna tuning is used.

[Ulysses HERNIOSUS]

Hi,

there are two features for competing for the AAT_A/B outputs. One is the analog config which switches the DACs according to the used operating mode and the tuning algorithm itself. We became aware of this issue and will make this more visible in upcoming versions of the software.

What you can do is:

1. Open the GUI and only afterwards connect the board (Important to do it in this order for this GUI!)
2. Go to Analog Config tab,
3. Read from board or Load from file a proper Analog Config
4. Remove registers 0x26 and 0x27 from POLL_COMMON and LISTEN_ON
5. Write To Board (Optionally also Save To File with a proper filename)
6. Now you can go to Polling tab and observe the effect of tuning using "Tune antenna when there are no tags"

Regards, Ulysses

[Mtaka.8]

​Hi,

thanks for your answer. I confirmed AAT in poling mode.

I have additional questions,

1. When are AAT(control voltages) output?　While the IC is wakeup?While polling? Only while the carrier wave is outputting?
2. Is the initial value of the AAT(control voltage) set or the last optimal value?
3. Is the AAT output off in Low power mode?
4. Could you exemplify [hardware based wake-up] described in your datasheet(DS12484 P15 Using hardware based wake-up in combination with the automatic antenna tuning feature is not recommended.)

[Ulysses HERNIOSUS · Accepted solution]

Hi

ad 1) Please see description of aat_en: The pins are driven to their value only when en=1 and aat_en=1. Otherwise they are weakly driven to some value.

ad 2) not sure what you mean: when en=1 and aat_en=1 then the AAT values are driven according to their corresponding register content. From SW side if they are not changed by the analog configs then they will keep their value.

ad 3) yes, see 1)

ad 4) We are working on an appnote which should be released in the coming weeks describing this problematic use-case.

Regards, Ulysses