Questions about ST25DV16 + Nordic 52832

[KLam.11]

Hello,

I'm using adafruit ST25DV module with Nordic 52832 as host MCU, and porting the code to host bases on the ST25DV_DISCOVERY_FW_V1.1.2 demo, then encountered below issues:

1) In the demo, after enabling FTM, host MCU will keep monitoring the it status MsgInMailbox by calling BSP_NFCTAG_ReadITSTStatus_Dyn but after porting, host MCU never get this interrupt but can get the RFPutMsg by calling ST25DV_i2c_ReadMBCtrl_Dyn when App sends data to ST25DV.

I can confirm I've enabled (ST25DV_GPO_RFPUTMSG_MASK | ST25DV_GPO_RFGETMSG_MASK | ST25DV_GPO_ENABLE_MASK) in GPO register, what other reason may cause this happen?

2) By monitoring RFPutMsg in ST25DV_i2c_ReadMBCtrl_Dyn in the code, host MCU can easily receive 256 bytes, 512 bytes data from App, but when App sends more data let says 16000 bytes, it keeps intermittent, App keeps retry and host MCU cannot get correct data from ST25DV, is it related to questions 1?

3) During testing, I keep monitoring every second on the RF field by calling ST25DV_i2c_GetRFField_Dyn, after the phone closed to the NFC antenna, in most cases, it returns FIELD OFF after few seconds, is the field not stable or somehow the phone will off the nfc field after few seconds if not data transfer?

Thanks,

Kevin

[KLam.11]

Hello Lebon,

We are using mobile phone as reader to transfer files to device, since the size of the device is quite small, we cannot use larger antenna. We will try to add a tank capacitor see it helps or not. Thanks for the suggestions.

Best regards.

[KLam.11]

Hello Lebon,

I have another questions regarding to the 100% amplitude modulation versus a 10% amplitude modulation referring to AN4913.

https://www.st.com/resource/en/technical_note/dm00190233-st25-nfc-guide-stmicroelectronics.pdf

According to above nfc guide, 10% AM is for VICC command, 100% AM is for VCD command on NFC-V (ISO 15693), is that correct? If that is the case, is that mean all the time running at 100% AM in Fast Transfer Mode?

Thanks and regards,

Kevin

[JL. Lebon]

Hello Kevin,

Actually, only the modulation amplitude from VCD to VICC communication is specified. Modulation amplitude from VICC to VCD is not specified in NFC-V or ISO15693 and really depends on a lot of external factors.

ISO15693 specifies that the VCD sends commands to the VICC using either 100% modulation or 10% modulation amplitude.

NFC Forum NFC-V (which can be seen as a subset of ISO15693) only uses 100% modulation amplitude for VCD to VICC communication.

(the guide is wrong saying that VICC to VCD is 10% modulation, I will ask for this to be fixed).

So, you can do Fast Transfer Mode in 100% or in 10%, it will work for both. It is up to the reader to decide which modulation amplitude to use. The ST25DV will support both modulation amplitude.

For energy harvesting, it is better to use 10% modulation because more energy is received by the tag during modulation phases.

Best regards.

[KLam.11]

Hello Lebon,

Thanks for the information.

In our application, smartphone is the reader, is it possible to set the App using 10% module always? If so, how? I tried to search such information in the Android App example source code in ST25NFCApplication_V3.6.0, but seems doesn't have.

In addition, according to below EH current delivery profile in AN4913, the ambient H field is one of the major factor that affecting the P_EH, what is the definition of H (A/m rms), is it related to the distance between reader and the antenna? and also 10% or 100% modulation amplitude used in this testing?

Thanks and best regards.

[KLam.11]

[JL. Lebon]

Hello,

Unfortunately, there is no API to change the modulation amplitude in Android. It is hard coded in low level drivers and most of the smartphones are using 100% modulation because this is what NFC Forum requires. So with smartphones, you are stuck at 100% modulation.

Concerning the H field, this is the measure of the magnetic field that the antenna receives.

In the application note, it is measured using an ISO tower, as described in the ISO10373-7 specification. It is a normalized way to measure the magnetic field power received by an ISO15693 antenna. RF field is measured in A/m.

The more A/m the antenna receives, the more power is available for energy harvesting. The magnetic field strength depends on several factors, but basically in the case of a smartphone, you can act only on the distance factor (H decreases with the cube of the distance).

Best regards.