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Connect SPI device through J15 Extension of OMAP L138 LCDK and interface it with C6748 via McBSP

Sajad Rahmdel
Expert 1705 points
Other Parts Discussed in Thread: OMAPL138, ADS1602, OMAP-L138

Dear Friends,

We have a custom SPI Device (It contains ADS1602 Analog to Digital Converter). We would like to interface (or connect) this SPI device to C6748  processor of  our OMAP L138 LCDK. To achieve this goal, we will use McBSP (Multichannel Buffered Serial Port). Our final goal is to transfer and receive data from this SPI Device to our OMAP L138 LCDK, and store the received data as an array of data. We are using the MCBSP example code in OMAPL138 package ,(pdk_OMAPL138_1_01_00_02\packages\ti\drv\mcbsp\example), as our starting point. As mentioned in Table.2 of (www.ti.com/.../spru580g.pdf), McBSP has the following interface pins.

My Question:

1. Which pin on the Extension of OMAP L138 LCDK is connected to the DR (received serial data), DX (Transmitted serial data) of the McBSP Peripheral?

2. I've already checked the OMAP-L138 LC DEV KIT VER  A7E (OMAP L138 LCDK schematics), but it seems to me that non of J15 and J14 extensions of OMAP L138 LCDK have a designated pin which connects to McBSP. Perhaps, should we use the SPI pins such as J15.21 and J15.23?

Thank you :)

  • 0
    TI__Guru** 116100 points
    Yes, you can use SPI interface directly to interface ADC.
    As you said, you can take SPI0 from J15.

    For that you have to remove the resistors R184, R179 and R178 and put 0ohm resistor in R214, R215 and R216 as SPI0 is muxed with MII pins (Ethernet)


    1. Which pin on the Extension of OMAP L138 LCDK is connected to the DR (received serial data), DX (Transmitted serial data) of the McBSP Peripheral?

    You can't take MCBSP0_DR0 and MCBSP_DX0 pins from LCDK boards as its connected to Ethernet PHY directly.
    You can take out wires from R92 and R93 resistors after removed them, it may damage your board.
  • 0 in reply to Titusrathinaraj Stalin
    Expert 1705 points
    Dear Titusrathinaraj,
    Thank you for your prompt reply.
    Unfortunately, we cannot use SPI0, because we are currently using this pin for ehrPWM1 output. As you know, ehrPWM1 is muxed with MII pins (Ethernet). The process is explained in details (by you!) in the following link:
    e2e.ti.com/.../531293

    My question: Is there any way that we use the SPI1 instead of SPI0? If yes, please elaborate your answer on how to do so.
    Thank you :)
  • 0 in reply to Sajad Rahmdel
    TI__Mastermind 43660 points
    Sajad,

    I understand your problem of using SPI0. Instead you can use SPI1 from J16 connector in LCDK.

    Regards,
    Senthil
  • 0 in reply to Titusrathinaraj Stalin
    Expert 1090 points

    When you say:

    "As you said, you can take SPI0 from J15.

    For that you have to remove the resistors R184, R179 and R178 and put 0ohm resistor in R214, R215 and R216 as SPI0 is muxed with MII pins (Ethernet)"

    does that mean we cannot use SPI0 and Ethernet at the same time if we make this modification?

    Is there any way to access SPI without modifying the board or using a ribbon cable?  

    Do you know of a ribbon cable that has signals broken out so they are easier to connect to?

    Thanks.

  • 0 in reply to James McLaughlin
    TI__Mastermind 43660 points
    James,

    When you have this modification you can access either SPI or Ethernet but not both of them at the same time. If you connect both the interface on the same bus, the interface may not work properly and it may lead to contention issues as the LCDK does not have mux device to operate this interfaces independently.

    Regards,
    Senthil
  • 0 in reply to Senthilkumar Srinivasan
    Expert 1090 points
    I see, that makes sense! Thank you