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Problem of TMS3705DDRQ1

TADASHI OMORI
Prodigy 10 points
Other Parts Discussed in Thread: TMS3705

nice to meet you
I am a consultant for a company in Japan.
thank you.

The company I am currently consulting for is:
TI's TMS3705DDRQ1 is used for short-distance data communication.

I'm currently having the following problem:

If you check the data received from the sending side with the CPU that received it from TMS3705DDRQ1
Data may be garbled.

There are also bit errors, and there are times when the data is misaligned, such as 8 bits.

I've been looking into various causes, but I still can't find the true cause.

Please let me ask the following questions.

1) TMS3705DDRQ1, such as reception data is garbled or bit-shifted
Are you having problems?

2) I don't know if this is the cause of the above problem of garbled received data,
The peak value (amplitude) at the end of the receiving antenna becomes very small depending on the timing.
phenomenon is occurring.

I've been investigating various things, but at least I can't see any change in amplitude on the sending side,
For some reason, there is a phenomenon that the amplitude becomes smaller on the receiving side.

Since the antenna end is directly connected to the data reception port of TMS3705DDRQ1,
If the input impedance at the data receive port of the TMS3705DDRQ1 is
It seems that the phenomenon that it is getting smaller due to factors is occurring.

Have you ever had such a problem before?

Also, if such a problem occurs, if you know the cause and countermeasure
Could you tell me?

In particular, does the power supply voltage of the TMS3705 change the peak value of the antenna? Is there any chance that the wave height will be particularly small?
In addition, please let me know if the antenna peak value will change due to interference waves.

Thank you very much.

  • 0
    TI__Intellectual 1055 points

    We recommend to measure receive signal at SFB pin and decoded transponder response data at SCIO pin.

     

    Best is to measure versus distance.

    At close distance the SFB voltage should be much higher at 5mVpp.

    SCIO signal during transponder response begins with start byte 81hex or 01hex (at SCIO) followed by data bytes.

     

    To your questions:

     

    1) TMS3705DDRQ1, such as reception data is garbled or bit-shifted

         Are you having problems?

                    TMS3705 has no such problems in low noise environment.

                    External noise can cause decode issue.

                    Please measure SFB signal level without transponder during response phase to see noise level.

     

    2) I don't know if this is the cause of the above problem of garbled received data,

         The peak value (amplitude) at the end of the receiving antenna becomes very small depending on the timing.

         phenomenon is occurring.

                    TI HDX transponder signal is getting smaller during transponder response.

                    Important is the signal level at end of response and also the length of the transponder response,.

                    which dependent on transponder type.

    What transponder type do you use?

    Please see also datasheet specification of Vsfb and figure 8.3 TXCT/SCIO signals.