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AFE7950EVM: Programming LMK via the SPI interface

Part Number: AFE7950EVM
Other Parts Discussed in Thread: AFE7950

Hi Team,

We've been looking into using an FPGA (ZC706, as per TI reference design) to program the AFE7950EVM over the SPI lines. For this process, two major components need to be programmed:

  1. AFE7950
  2. LMK on the EVM

As far as I understand the AFE7950 EVM should be fairly straightforward to program as there are some SPI lines going from it to the FMC on the EVM. However, the LMK, if I understand correctly, is being programmed solely via the USB connection with PC (and Latte) and there are no dedicated LMK SPI lines going to the FMC. Can you confirm if this is the case, and if so, could you suggest some measures that can be taken to connect LMK with FPGA through SPI lines?

Kind regards,

Željko

  • Hi Team,

    Is there any follow-up on this?

  • Hi Zeljko,

    You are correct, the AFE SPI connection is easy as the AFE SPI lines are directly connected to the FMC connecter. To program the LMK from the FPGA we had to connect a wire from the LMK SPI to a open GPIO signal on the FMC connector. This means that you should check the FPGA dev kit schematic and see what open FMC pins are connected on both sides but are not used. Then you can modify the board so that the LMK SPI is routed to these lines.

    Regards,

    David Chaparro 

  • Hi David,

    Thanks for the detailed answer.

    I wanted just to additionally check if you could let me know what kind of setup (mostly the FPGA) were you using when you were connecting the LMK with the FPGA. Additionally, if it's possible would you be able to share the schematics and the details of the modifications you made on the FPGA/AFE sides so I can compare it to our planned mods?

    Kind regards,

    Željko

  • Hi Zeljko,

    The board modifications that were done are the following.

    1. Use a wire to connect the LMK SPI_SCK to the AFE SPI_SCK. Solder a wire connecting R248 and R88.

    2. Use a wire to connect the LMK SPI_SDIO to the AFE SPI_SDIO. Solder a wire connecting R249 and R87.

    3. Use a wire to connect the LMK SPI_CS to an open pin on FMC connector. Solder a wire connecting R242 to open pad of R9 on FMC connector side, D26 on FMC connector. 

    Regards,

    David Chaparro