TRF7970A: Working with multiple antennas/reader/mcus

Hello Jason,

"I can't answer your question about power yet as i'm too early in the design process. However could I get around this by simply using a couple more Transceivers and reducing antenna numbers on each one? 3 Transceivers each with 8 antenna for example?"

• Perhaps I misunderstood you earlier so lets make sure we are on the same page about what caused me to bring up the power aspect:
  • You mentioned in the original post that up to 24 tags may be presented at one time. Is this figure for a SINGLE antenna, or spread across the network for antennas? If the latter, what would be the most tags you'd expect presented to a single antenna?

"What is the best MCU for me to use? "

• The MSP430F5529 probably is a bit overkill for this application to be honest, but depending on many muxes you need, you will need an MCU with sufficient GPIO to handle that, so be mindful of that.

"If i had to I guess i could simply read the UIDs, however this would require me to apply attributes to those somewhere in code in order to differentiate what type of object is giving me that UID?"

• If you need to differentiate objects, unless you have a full Look Up Table for specific UIDs, you'd need to store some data in the tag. ISO15693 has a block data format, so it wouldn't be hard to store a few blocks of data (each block is typically 4 bytes of data) to help identify the tag.
• The UID in this application would be used so you can send addressed commands to a specific tag and get a reply from it, so you can go around and in a controlled  order read data from every tag in your RF field

"I'm surprised to see that nobody has created a library for the TRF7970 for Energia? or have I just not found it. In order for me to use the NFClink library in CCS I would have to use the TI compiler which i currently don't have and think i'd run out of skill if i tried to port that to the GCC or Energia myself?"

• Yeah we don't have an Energia example at this time, it's a bit tricky to do the NFC stuff in Energia because it was never designed with Energia in mind, and so we haven't got around to that.
• For your use case actually, you will want anticollision, and that is not featured in the code which runs on the MSP430F5529. However, we have a low resource RFID reader/writer example that includes full anticollision support for ISO15693 which I think is more suited to what you are trying to do and should be easier to work with as well:
  • http://www.ti.com/lit/zip/sloc297
  • This uses the same BoosterPack you have along with the G2 LaunchPad (MSP-EXP430G2) which you may already have too.

"Aside from all this, is multiplexing antenna the right way to go? instead of multiplying the number of transceivers?"

• Multiplexing will be cheaper, the only way I'd see needing more transceivers is if from a speed standpoint you need to read tags faster than you can while toggling through the 24 antennas.

"Is the TRF7970 the best ic to use? my use of the RFID would be simple. I would only ever read passive tags, and if as you said 15693 gives me the best collision detection then the other protocols on 7970 are no use to me are they?"

• The TRF7970A is what you should START with for evaluation, as that is where we have our hardware and collateral available. However, for ISO15693 only applications, you can use the TRF7962A which only support ISO15693.
  • The TRF7962A would require some small change from a firmware level, as it has a smaller FIFO, a few different registers, and there is a little errata deal with the SPI polarity that needs to be address (just toggling the polarity between read and write operations)
  • If you think you'll want to use the 62A, I can provide some software (based on the sloc297 example above) for you to work with that would let you toggle between 70A and the 6xA devices with a single change. Let me know.