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TRF7962A: TRF7962A

Rotem Sasporta
Intellectual 265 points
Part Number: TRF7962A

Hi,

with regards to TRF7962A PCD, we would appreciate that this would be given a high priority since it is a pressing matter to the customer.

 

We currently using TRF7962A to communicate with ISO/IEC 15693 tags, We've found that in most our tags, When we read the RSSI Levels and Oscillator Status Register, we get that the Auxiliary channel is higher considerably then the Main channel (4-12 dBm).

 

According to the datasheet there is an indiscrepancy about the Auxiliary channel description: on the one hand it is described "Only the main receiver is used for reception; the auxiliary receiver is used for signal quality monitoring."

On the other hand: "The MCU can read the RSSI values from the TRF7962A RSSI register and decide if swapping the input signals is preferable or not."

 

We've tried to use the Auxiliary channel by setting the Chip Status Control register, and even though we can see the changes made in the RSSI register, there is no physical change in the distance we are able to read the tag (should be greater according to the RSSI levels).

We've even shorted the main channel and still were able to read and write to Tag (The chip was set to use the main RX), so it seems that the RX came from the Auxiliary even though it was not set.

 

The question is, How can we use the Auxiliary channel, and can it be used for read and write commands? If so, Should we see a difference in distance we are able to read the Tag?

 

 Please advise ASAP

BR,

Rotem

  • 0
    TI__Guru*** 131180 points

    Hello Rotem,

    The datasheet doesn't have an discrepancy:

    "Only the main receiver is used for reception; the auxiliary receiver is used for signal quality monitoring."

    So the Aux channel is used for signal quality monitoring.

    "The MCU can read the RSSI values from the TRF7962A RSSI register and decide if swapping the input signals is preferable or not."

    The RSSI is the result of the signal quality.

    Therefore, reading the RSSI values is linked to signal quality and thus the auxiliary channel is doing what is described.

    Now then moving on to other points, first off can they specify if they are looking at the Internal or the External RSSI? What values are they getting for this on the SPI bus?

    What is the current tag reading distance? What is the size of the tag? What is the reading distance they are trying to target?

    Regarding the test of shorting the main channel, we have never done this so I have no idea if that result makes sense. For now, that test isn't relevant to me, at least not until I understand more about the questions I asked above.

    For the questions:

    • How can we use the Auxiliary channel, and can it be used for read and write commands?
      • The auxiliary channel is either RX_IN1, or RX_IN2, based on the settings of the Chip Status Control Register. The main channel selected will be used for read/writing. But you can change which channel is the main channel between RX_IN1 and RX_IN2 via the Chip Status Control Register so either RX_IN1 or RX_IN2 can be used as the main channel.
    • If so, Should we see a difference in distance we are able to read the Tag?
      • Building on what I said for the prior question, the only times that changing channels from RX_IN1 to RX_IN2 would improve performance is when in a noisy environment where the signal degradation on one line is more notable than the other due to the points at which they are tapped from the matching network and how they are routed internally in the device. It is very rare that is feature provides better read ranges. If they answer my previous questions though, I can try and help guide on the right steps to take to maximize read range.