NHS3100 app_demo_label_signed_url only working while battery powered

[HasseF]

Hi!
I'm working on an application based on the NHS3100 and the demo code 'app_demo_label_signed_url only working while battery powered'

I have managed to send the temperature data to our own Web-server as well as get the temp data displayed on the web-page. (thanks for the included .html and .JS code), however. The NHS3100
will only work while connected to the LPC-LINK 2. And data is updated only while pushing the reset button.

Any tips ?

[HasseF]

Thank you Patrick

I searched around in the office and found a second NHS3100TEMOADKUL module.
And on this unit, Yes the signedurl code works battery-less. I operate it with an iphone 13 mini...

So i have two similar unit one works battery-less, one only with battery/external power...

Not really what we wanted to see since we are working with a project, supposed to be produced in really...really high volumes,
single use, low cost, printed and disposable board....there will be no room for individual antenna tuning...

Do you know of any reference/demo board PCB-files for download, that could give us a jumpstart  with the NHS3100. Alway nice to start
the design work from a working reference. in particular if the antenna design is as picky as it looks from our two NHS3100TEMOADKUL boards...

//HasseF 

[patrickgeens]

Hello HasseF,

Sorry for the late reply, I wanted to get hold of an iPhone 13 mini to run some tests on boards we have in the lab. Reading distance with the demo board is about 1cm  ... 1.5cm.

But that doesn't solve the issue with 1 of your boards:

Since the data transfer via NFC was successful when the demo board was fed via the LPC-LINK2, I assume the NFC block and the ARM core are working correctly, at least the data path.

If no metal was added in the vicinity of the NFC antenna, the antenna tuning should be sufficiently close for good operation.

I would like to propose the following test on the initial board:

- flash and run the "app_closed_nvmeraser" firmware from the SDK to erase all non volatile memory. (the led blinks 3 times during operation)

- flash the unmodified "app_demo_label_signedurl" firmware

- install the NXP TagInfo app (https://apps.apple.com/us/app/nfc-taginfo-by-nxp/id1246143596) on the iPhone.

- remove the battery if installed, disconnect LPC-LINK2

- scan the tag with the TagInfo and check if it finds an NDEF message in the NFC memory

If possible, repeat with an Android phone (they typically have a larger NFC antenna)

Kind regards,

Patrick

[patrickgeens]

Hello HasseF,

I suspect the supply voltage taken from the NFC antenna drops too low, resetting the chip before the upload of the data to the phone.

The supply voltage dips under load are due to the impedance of the antenna and supply block in the chip multiplied by the current drawn.

When power is taken from the LPCLINK2, the supply impedance is much lower than when NFC only is used, making the voltage dips much smaller. Secondly the voltage derived from NFC is 1.85V instead of 3.3V, so there is less margin for dipping on NFC

The fact that only 1 measurement is sent after pressing reset is by design of the firmware (it expects the chip to become unpowered and thus reset when the user removes the phone)

Possible reasons:

- current consumption too high due to extra load: additional HW blocks activated, external loads (sensors, leds, ...), system clock increased.

- impedance of the NFC antenna too high: narrow tracks of high resistivity material (printed ink), resonance frequency too far from 13.56MHz

Kind regards,

Patrick

[HasseF]

OK

I'm using the 'NXP NHS3100TEMOADKUL' Development kit.
So your reply states that this kit is not valid for batteryfree NFC applications, Right ?

Can you recomend any other NHS3100 kit for work with
battery-free applications?

// HasseF

[patrickgeens]

Hi HasseF,

I just double-checked a few times with the NHS3100 board as shown in the photograph and the SDK12_6 signed url demo app. Board functionality and website are OK.. (Tested with Android Samsung A52s.)

Can you share which reader/phone type you used?

The application was tested with Android and iPhone devices.

Kind regards,

Patrick