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TRF7964A SPI Interface

Luis Fernando Higareda Amezcua
Prodigy 10 points
Other Parts Discussed in Thread: TRF7964A

Hi,,

I´m trying to communicate with the TRF7964A by SPI,, but I never got a response from TRF7964A. I´m trying first to read some registers,, I checked the SPI signals with an osciloscope and the signals I´m sending make match with the signals that are in the datasheet with the only exception there is no response. Can you please help me with this issue? I am not going to use OOK/ASK, MOD and SYS_CLK pins. VDD = 3.3V and VCC = 5V. I also checked in the osciloscope the SYS_CLK pin and I found a square wave form of 3.4Mhz and I´m using a 13.56Mhz crystal.

This is the schematic,, am I missing something?

  • 0
    TI__Guru* 91086 points
    yes - you are missing several things - you need pull downs on ASK/OOK and MOD pins. 1k Ohms will work. you need bulk and bypass cap pair on VDD_X.

    you also have option of using VDD_X for VDD_I/O supply voltage as well.

    C6 needs to be 10pF, C9 needs to be 680pF, C11 needs to be 27pF. Then you should also show your matching for antenna back to 50ohm point A1.

    then we can move on to your register settings when you get this repaired.