ST25R3916 using AAT and Hardware wake-up

[COles.1]

Hi, I have a issue with the ST25R3916 when using the AAT and the Hardware wake up functions together.

The tuning works fine and finds the best parameters, then when entering sleep mode the parameters changes to a fixed value. When waking up the first time the outputs for aat_a and aat_b goes back the tuning parameters, but every wake up after outputs for aat_a and aat_b are just 2V.

How can I get the ST25R3916 to use the tuning parameters every time?

And why does ST not recommend using these two features together?

I have looked in the example projects for the IC but there the AAT is not used.

Below some scope images of the AAT_B output (Yellow, green is data transfer).

AAT with an antenna with capacitance and the first card read.

AAT of antenna with high capacitanceFirst and second card read of antenna with high capacitance.

Also if any have a quick explanation/link to an note of why the voltage always is at 1.5V every time there is data transfer (Green line). I will appreciate that as well.

[Ulysses HERNIOSUS]

Hi COles.1,

DAC/AAT values are by default defined inside the Analog config. Even if you run the algorithm as soon as you communicate the values inside Analog Config are prevailing. Please refer to AN5322 chapter 8(.2) for some details and how to avoid these effects.

The AAT pins are are also not driven in power-down mode of the ST25R3916 (en=0).

I am not completely grasping your scope shots: What is the green line (you said data transfer.. Is this reader modulation or tag load modulation? And where did you connect it?)

Best Regards, Ulysses

[COles.1]

Hi.

Thanks for the AN it gave information.

I don't have any of the kits referred to in the AN. We are using nrf9160 with zephyr.

I believe the read from file solution will work, but where can I get the "pre-built configuration files named “MB1414…_for_aat.xml�?" it refers to in the AN, didn't have any luck on st.com.

In the RFID we have these included files where I can see predefined values in the file: rfal_analogConfig.h.

in this const array with default values, i tried to remove the parameters for the ...ANT_TUN_A/B but it didn't work.  

The green is the reader modulation, it was connected to one of the wires to the antenna print. the images was just for visualization of the aat_b output.

[Ulysses HERNIOSUS · Accepted solution]

Hi,

the MB1414…_for_aat.xml is part of stsw-st25r010 - the PC GUI. I can attach the xml files - they are more or less directly translatable into rfal_analogConfigTable.h. In that file you will need to remove all the occurrences of ST25R3916_REG_ANT_TUNE* (4 occurrences, 8 regs overall).

Best Regards, Ulysses

[Ulysses HERNIOSUS]

Hi,

I may have missed a small part of your question:

AAT_A/B pins are not active while en=0. If you want to save power while performing Wake-up you would typically set en=0 which causes a change in matching. For getting the values back before emitting the Wake-up pulse you would need to accommodate some settling time in software.

Best Regards, Ulysses