Actions
Forum Thread Details
  • State Not Answered
  • Replies 19 replies
  • Subscribers 288 subscribers
  • Views 2928 views
  • Users 0 members are here
Related
See a helpful answer?

Be sure to click 'more' and select 'suggest as answer'!

If you're the thread creator, be sure to click 'more' then 'Verify as Answer'!

Trying to understand NFC ASK Modulation

BigG

According to my Google search, NFC uses ASK modulation to transmit data:

https://www.rfwireless-world.com/Tutorials/NFC-Near-Field-Communication-tutorial.html

https://www.rfwireless-world.com/Tutorials/NFC-Modulation-and-NFC-Coding.html

Which I have interpreted as the following where the "Mixing Circuit" includes the NFC tuned antenna and two picoFarad capacitors... but what else is needed.

image

As a non electronics engineer I am trying to work out a minimum circuit required.

Then my lofty intentions is to use a Raspberry Pi Pico to generate my clock signal using PIO and as there is also a Manchester Encoding PIO example, I will attempt to use that too.

So could this work, I wonder?

Parents
  • 0

    Hi Colin,

    If all you require is ASK, then the circuit would be just a gate or switch (if the 13.56 MHz signal is not coming from the Pico). If you're generating the 13.56 MHz signal from the Pico somehow, then for ASK it just needs to be switched on/off in software. 

    I've no idea if this would work though, I've never studied NFC at this low-level, and don't know if it requires bidirectional comms or anything else. Also, the output signal would be very low, since the Pico GPIO can't provide a lot of power, so then you'd need an amplifier.

    The capacitor(s)/inductor usually form a resonant circuit, but it wouldn't ordinarily be connected to a GPIO. The resonant circuit is part of an oscillator, which is usually created with (say) a transistor of some sort, i.e. it's a different topology that isn't contained within the Pico, and not normally directly drivable by the Pico either, instead it becomes part of a frequency synth circuit (which isn't all that easy to build without using a dedicated chip). In your case, if you're trying to use a Pico for this, then you may as well connect an amplifier to the Pico, and drive the inductor with that. I think it's unlikely to work though (but I don't know for sure! I could be totally wrong, since I know ~zero about this), I'm guessing NFC protocol is more complex.

Reply
  • 0

    Hi Colin,

    If all you require is ASK, then the circuit would be just a gate or switch (if the 13.56 MHz signal is not coming from the Pico). If you're generating the 13.56 MHz signal from the Pico somehow, then for ASK it just needs to be switched on/off in software. 

    I've no idea if this would work though, I've never studied NFC at this low-level, and don't know if it requires bidirectional comms or anything else. Also, the output signal would be very low, since the Pico GPIO can't provide a lot of power, so then you'd need an amplifier.

    The capacitor(s)/inductor usually form a resonant circuit, but it wouldn't ordinarily be connected to a GPIO. The resonant circuit is part of an oscillator, which is usually created with (say) a transistor of some sort, i.e. it's a different topology that isn't contained within the Pico, and not normally directly drivable by the Pico either, instead it becomes part of a frequency synth circuit (which isn't all that easy to build without using a dedicated chip). In your case, if you're trying to use a Pico for this, then you may as well connect an amplifier to the Pico, and drive the inductor with that. I think it's unlikely to work though (but I don't know for sure! I could be totally wrong, since I know ~zero about this), I'm guessing NFC protocol is more complex.

Children
No Data