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TPS92682EVM-069: Trying to communicate with TPS92682EVM-069 board with RH850 eval board using SPI Communication

Saraswati Khollam
Prodigy 10 points
Part Number: TPS92682EVM-069

Tool/software:

Hello,

Hello TI Community,

I am working with an RH850 microcontroller (part number R7F701684) and trying to interface it with the TPS92682EVM-069 LED driver evaluation board via SPI. My goal is to read the default register values from the TPS92682 using the SPI interface.

TPSboostMaster (2).zip

Setup:

  • MCU: RH850 (R7F701684)

  • Peripheral: TPS92682EVM-069

  • Interface: SPI (configured according to MCU datasheet and example code)

  • SPI Mode: Configured with CPOL=0, CPHA=0(as per TPS92682 datasheet recommendation for read/write transactions)

  • SPI Clock: ~1 MHz

  • EN pin on TPS92682: HIGH (>2.5 V)

  • Tested the SPI driver in loopback mode on RH850: works correctly

Problem:
When I attempt to read any register from the TPS92682, I consistently receive garbage values (e.g., 0x0F04, 0xFFFF) instead of the expected default values. This happens even for registers that are supposed to have known default states.

Request:
Can someone please guide me on the correct approach to reliably read default register values from the TPS92682 using RH850? Any insights on SPI frame assembly, timing requirements, or known quirks with this evaluation board would be extremely helpful.

Thank you in advance!

  • 0
    TI__Mastermind 23456 points

    Hello Saraswati,

    How are you connecting the SPI signals to the TPS92682EVM-069?  Do you have the schematics of RH850 EVM you are using?  Please given connection diagram between boards, power supplies, and loads.     

    Pease capture waveforms on an oscope for MISO, MOSI, SCLK, and SSN on the 682 board.  We want to verify signals seen by the 682. 

    Lets make sure we don't have bus contention, week pullup, or some other unexpected signal.  

    Our EVM has digital isolators (U2 and U3 in the EVM schematic) and if you don't connect correctly to the board then you can have issues.  

    -fhoude

  • 0 in reply to fhoude
    Prodigy 10 points

    Hello Fhoude.

    This is my RH850 board user manual.

    r12ut0004ed0110-rh850f1km-s1.pdf

    Connection between two boards is given below.

    RH850 board        TPS92682-069(EVM board --J10 connector is used)

    Clock(P0_2)         Clock (PIN no 12)

    MOSI(P0_1)         MOSI(PIN no 8)

    MISO(P0_3)         MISO(PIN no 10)

    SS(P8_2)             SS(PIN no 14)

    I am not able to capture waveforms at TPS 92682-069 EVM board. but i can see waveform at my RH850 board.

    given is attached screentshot.

     

  • 0 in reply to Saraswati Khollam
    TI__Mastermind 23456 points

    Hello Saraswati,

    You need to make sure those signals get to the is getting to the device.  I also can't see these screen shots too well because they are too small.   I don't think I am seeing MOSI?  Where is that? 

    Also, I said scope shots to make sure we don't have a pullup resistor issue or bus contention issue.  MISO is open drain so maybe you need to change pullup.  Logic analyzer is fine once you have verified good signals coming and going to the 682 device.  

    I think you are having bus contention because of U2 and U3 being powered up on the secondary side via VDD.  That means the outputs are driven and it will fight with your MCU.  You should be able to see this in the waveforms.  The easiest thing to do it just remove U2 and U3 from the board.  You may want to read the datasheet of the digital isolators so you know how they work.  

    -fhoude