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CC2340R5: Evaluate if this chip can drive TFT LCD

Guangwen Zhou
Prodigy 50 points

Part Number: CC2340R5

Tool/software:

Hi Expert,

LCM w/ SPI interface is proposed to use in our program.

  • since the CC2340 just supports one SPI interface, we want to share the SPI interface w/ the external flash. the diagram is in below. SPI speed is better to configured more than 10MHz.

  • the display resolution is 60*100, and the bit depth is 16 bits. if we use SRAM for the display buffering, it might need 24KB SRAM for the buffering(double buffering). it seems the SRAM usage is too big for our application. I'm wondering if can use uDMA feature to directly transfer display data(eg: image) from external flash to the LCD module over SPI interface.

could you please help to evaluate the possiblity of using CC2340R5 to drive LCD? Thanks.

BR,

Guangwen

  • 0
    TI__Genius 10230 points

    Hi !

    You can use both the external flash and the TFT LCM using one SPI interface, but not at the same time since they use the same POCI/PICO pins. You will therefore be responsible to write code to make sure that they are not both running at the same time, for example with semaphores and controlling the CS pins manually through GPIO.

    The uDMA only allows transfer from memory to memory, peripheral to memory, memory to peripheral, but not peripheral to peripheral, so you will not be able to use uDMA for transfering data from your external flash to your TFT LCM.

    If you're worried about the lack of memory in SRAM, you could use a CC2340R53 device instead of a CC2340R5, since the CC2340R53 has 64kB of SRAM instead of 36kB, which should be enough to cover for your double buffering needs.

    Kind regards,
    Maxence

  • 0 in reply to Lea
    Prodigy 50 points

    Hi Maxence, 

    Thanks for the answers. 

    regarding the SPI application, we will use different chip select pin but shares the CLK and data pins. suppose this could work.

    One concern is the SPI configurations are different for these 2 peripherals. the external flash is a 4 wire SPI(CS SDO SDI SCK), and the LCM is a 3 wire SPI(CS SDIO SCK). in this case, 1 SPI interface could meet the requirement?

    BTW, regarding the SPI interface, can it support dual-SPI mode?

    BR,

    Guangwen

  • 0 in reply to Guangwen Zhou
    TI__Genius 10230 points

    Hi !

    As long as you want your peripherals to run at the same frequency, sharing the CLK pin will be fine.

    For the PICO/POCI pins, sharing those is very common, and it's a setup called Parallel SPI

    The only problem you might face is that our SPI drivers do not support 3-wire SPI (CS SDIO SCK) if DIO is bi-directional. I don't think this is the case for a TFT LCM, as the screen peripheral don't have a need to communicate send messages to the controller. If that's the case, you might need to modify the SPI drivers yourself to change the pinmux of the SDIO pin from POCI to PICO when needed. This is not very hard to implement, but it's something to keep in mind.

    Kind regards,
    Maxence

  • 0 in reply to Lea
    Prodigy 50 points

    HI Maxence,

    The information is important for us. Thanks.

    what about the SPI mode, suppose the SPI can't support QUAD mode. but how about the DUAL mode?

    BR,

    Guangwen

  • 0 in reply to Guangwen Zhou
    TI__Genius 10230 points

    Hi !

    The section about SPI in the Technical Reference Manual for the CC2340R5 (link) nor the TI SPI driver API for the CC2340R5 (link) do not mention QUAD or DUAL mode, so I assume that these modes are not supported.

    Kind regards,
    Maxence

  • 0 in reply to Lea
    Prodigy 50 points

    Hi Maxence,

    Many thanks for the confirmation.

    BR,

    Guangwen