I am researching using NFC for a high speed, non-contact sensor communication link. In this case, power is not necessarily being supplied through NFC (our current design uses a low frequency inductive power scheme which we may keep).
The requirements for this sensor are pretty extreme. 5000 Hz measurement rate with a 0.2 mS latency. I have looked at the NXP PN7150 and the TI TRF7970A controllers so far.
The fastest bit rate in Peer to Peer mode seems to be 424 Kbps. It looks like I am going to have to use passive mode and combine 2 measurements per packet to get the desired measurement rate. However this results in a 0.4 mS latency (this with a payload of 4 bytes per measurement).
Questions:
- Is peer to peer the best way to do this? Tag emulation can support 848 Kbps, but I am having a hard time getting my head around how this works with a fast packet rate. The TRF7970A eval system I have played with seems to take a very long time to read a tag.
- Is it possible to run the Peer to Peer mode at 848 Kbps? I realize this is not supported in the P2P standard, but this is not a general purpose P2P system. It is for a captive non-contact sensor that is only used with our equipment.
- Our sensor must operate with large pieces of metal in close proximity. I plan on using ferrite shielding, but is the passive mode more effected by this than active? From my limited understanding, it feels like active mode should be able to operate better in the presence of interfering metal, but I confess to limited understanding (this is my first NFC project).
- The TRF7970A documentation claims that a 1 mS delay must be inserted between collision detection and sending a packet in the active mode. Is this a recommendation or is it built into the hardware? If I am doing one way traffic (transmit only) can I bypass the 1 mS delay?
Any suggestions or help would be very appreciated
