Trouble getting a read with smartphones

hi, it’s been three weeks now that i have the Red xSIID in my forearm. unfortunately i don’t have enough fat in my hands and the veins are too oddly located that i decided with my Doctor to place it. The healing went without complications and via the ACR122u it works well on Ubuntu and Windows with it. Unfortunately, so far no smartphone (i’ve testet three different models) reads or write on the chip. But always the LED responds! Do you have any idea what could be the problem? best regards

can you describe how it responds? does it blink or does it come on solid?

which smartphone models have you tried?

Its always blinking

CatS41, Samsung, Huawai

Check out the

I linked to, find your modes of the phones you mentioned, and follow the link to the posts that mention their performance and hopefully the antenna location

Outside of that, we probably need to take a step back;
Apologies in advance, it is suck eggs time, but just to make sure we haven’t missed anything obvious, don’t worry if you did, you wont be the first or last …
Have you:-
Removed phone cover?
Turned on NFC?
Phone unlocked?
Screen on?
When you scan are you moving VERY slowly to different positions and orientations?

Are you using NXP TagInfo or similar to try and read?

ok it must be constant light, not flashing… as when accessing the ACR… thanks for u’re qick reply …

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yes i have nfcTools, NXP TagInf, and Mtools in use… with standard NFC cards it works smoothly with all smartphones

This is the CatS41 tear down, and this :red_circle: is ideally how you should be presenting your xSIID
Interestingly, the NFC antenna is installed in the back cover :large_blue_circle:

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flashing means the xSIID is near enough the NFC antenna coils of the phone to draw power to flash the LED each time the phone probes for NFC tags with its NFC radio… but the alignment of the xSIID is not good enough to power up the LED and the chip also.

You can also try the xFD that you would have received in your order to test your Antenna location and best orientation for reading / writing


You will also see how the NFC works on your phone. eg. My Samsungs throw out about 4-5 low power pulses and then 1 much stronger pulse and repeats.
This is very easy to see with the xFD or Diagnostic Card.

It is also good to confirm that your NFC is functioning correctly / on etc

Yes I use the xFD . that works

another guess from my side is that the chip is maybe implanted a little too deep… hopefully not … hehe

Possibly, coupling is really important.

Using the same orientation you found with the xFD, can you use your phone and press down “hard” and try to read with TagInfo

Me too

Also, what are you trying to do with your xSIID? What is your end goal?
business card?
Rick Rolling?
Smuggling less than 2kB of data across international borders to sell to foreign intelligence agencies etc?

I just tested the xFD again on the cat41… that also does not get a constant signal… probably the shell is just too thick… as I said with the ACR 122U everything works smoothly … maybe i should just buy a new phone :slight_smile:

This is expected. The xFD is just a coil and LED, with no chip. The phone will probe for chips a few times a second, hence the flashing… but if no chip is found it just keeps probing. When a chip is found, the field is turned on constant (like the ACR122U) so the phone can maintain communication with the chip. This probing behavior is a power saving technique used by the phone, but the ACR122U does not use this method, so it just keeps the field on constantly.

So, because the xFD has no chip, it will always flash. The xSIID does have a chip, so the LED will flash when drawing some power, but once the chip has enough power to start communicating, the phone should turn the field on and the LED should remain solid.

Make sense?

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ah yes… of course make sense

Have look through this thread, It will have some images and videos of what to expect, and what to try

it’s just for testing and getting used to it. i actually travel a lot and it’s already practical to have some essential data in my arm. a few small possibilities for remote control are already possible. the end goal would be an additional chip or sensor that i can use for live modulation of sound…

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