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AM6442: 9 bit SPI data transfer

Chris
Intellectual 301 points
Part Number: AM6442


Dear TI team,

We are currently seeking a Display device for our application. As the AM64xx series lacks a display controller, our approach involves utilizing SPI for communication with an external display device. Among the potential options, we have narrowed down to a few that offer 3 Line SPI support. However, it's worth noting that the initial communication frame requires 9 bits of data. Our main concern is whether the AM6442 SPI & driver for Linux can accommodate this particular data transfer configuration. I have observed that the data buffer support is available for 8, 16, and 32 bits. Does this mean that the data size granularity for data transfers is based on bytes?

The display device (WF35UTYAIDNN0) is equipped with the ILI9488 controller, and the provided sample transfer operation illustrates the usage in 3-line SPI mode. I would appreciate your advice on how to proceed.

Thank you

Chris

  • 0
    TI__Guru**** 205010 points

    Hello Chris,

    Thank you for the query.

    Chris said:
    Our main concern is whether the AM6442 SPI

    Please review the below sections in the TRM to understand the capabilities

    12.1.4.1.1 MCSPI Features

      The MCSPI modules include the following main features:

    Serial clock with programmable frequency, polarity, and phase for each channel

     Wide selection of SPI word lengths, ranging from 4 to 32 bits

      

    12.1.4.6.17 MCSPI_CHCONF_1 Register (Offset = 140h) [reset = 00060000h]

     

    11-7

    WL

    R/W

    0h

    Regards,

    Sreenivasa

  • 0
    TI__Guru**** 205010 points

    Hello Chris,

    Based on quick internal check we do not seem to have considred these use cases as part of the driver implementation.

    Chris said:
    driver for Linux can accommodate this particular data transfer configuration

    Do you have a setup to do some quick check?

    The diagram you attached in the above message - is that for the LCD?

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Intellectual 301 points

    Thanks 

    Kallikuppa Sreenivasa said:
    Do you have a setup to do some quick check?

    No, we need to decide based on the support by AM64xx. There are only limited options for displays with SPI interface. From the above responses what I understood is, it is capable for 9-bit transmission, but not the driver right?

    Kallikuppa Sreenivasa said:
    The diagram you attached in the above message - is that for the LCD?

    Yes, The target device SPI communication frame expects 9-bit transmission. One bit for Data or command identification and 8 bit actual data. ILI9488 is the controller

    Thank you

    Chris

  • 0 in reply to Chris
    TI__Guru**** 205010 points

    Hello Chris,

    Thank you.

    Yes, the target device SPI communication frame expects 9-bit transmission. One bit for Data or command identification and 8 bit actual data. ILI9488 is the controller

    Thank you. Any reason the pins are named SDA and SCL - these are names used for I2C.interface. 

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Intellectual 301 points
    Kallikuppa Sreenivasa said:
    Thank you. Any reason the pins are named SDA and SCL - these are names used for I2C.interface. 

     May be they have taken it as Serial Data (SDA) as a common for input and output instead MOSI and MISO

    Chris said:
    what I understood is, it is capable for 9-bit transmission, but not the driver right?

    I also found FIFO shall not be used in such cases. Would like to know whether DMA is possible with different word size like 9bit case?

    I have seen a star-bit concept. It looks like that is closer to our requirement.

    In both cases, we would like to know the Linux driver support . Can you confirm these points

    Thank you

    Chris

  • 0 in reply to Chris
    TI__Guru**** 205010 points

    Hello Chris,

    Thank you.

    Chris said:
    In both cases, we would like to know the Linux driver support .

    Based on my quick internal check, we don't seem to have the 9-bit interface related implementations in the drivers, or any tests done.

    regards,

    Sreenivasa