What do the pins "/CS", "SCK", and "SDI" mean? From my bad understanding of this diagram, I only have to run 3.3V to "/CS", "SCK", and "SDI". Is this true or am I way off?

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enter image description here Let me know in the comments if you would like more details. Here is the Link: http://www.newhavendisplay.com/specs/NHD-3.5-320240FT-CSXN-CTP.pdf

  • 3
    \$\begingroup\$ These should be documented in the datasheet. From the common knowledge - "/CS"="(Active Low) Chip Select", SCK and SDI are SPI Clock and Data In signals. \$\endgroup\$
    – Eugene Sh.
    Commented May 16, 2019 at 16:29
  • 2
    \$\begingroup\$ Was this diagram supplied to you by the manufacturer, or did you draw it? \$\endgroup\$
    – mike65535
    Commented May 16, 2019 at 16:31
  • 1
    \$\begingroup\$ Welcome! Please provide a link to the datasheet, or at least a part number. \$\endgroup\$
    – bitsmack
    Commented May 16, 2019 at 16:38
  • \$\begingroup\$ I added a link, this is the Manufacturer print. I am trying to bypass the extra chips and directly communicate with the LCD interface/ TFT Display \$\endgroup\$
    – cch
    Commented May 16, 2019 at 16:42

1 Answer 1


/CS is Chip Select, which is used when you connect multiple devices to the same SPI bus. Also, the "/" means that it is an active low signal, so you need to tie that pin to GND if you want your device to receive data. SDI and SCK are the data and clock lines used for SPI communication. By tying the 3 pins to +3V3 you are pretty much disabling the SPI communication port.

That display uses the R[7:0], G[7:0], B[7:0] pins to send the pixel data and the HSYNC, VSYNC and PCLK pins to control the timing of pixels and lines. All those signals need to be synced perfectly, which is why the manufacturer is using the FT813Q video controller. If you want to 'manually' control the display for experimental purposes, I'd recommend using an FPGA since you could have better control of the timing.

  • \$\begingroup\$ Thank you for the response! So could I run the LCD display with an FPGA ? and would I need to use the SDI and SCK or could I tie them to 3v3 and forget about them and use just the RGB, HSYNC, VSYNC and PCLK pins to run the LCD \$\endgroup\$
    – cch
    Commented May 16, 2019 at 17:57
  • \$\begingroup\$ You should be fine without the SPI line since the FT813Q doesn't use either. Regarding the FPGA, the main concern is that without the datasheet for the LCD display I wouldn't know what voltage levels it uses or what frequencies it uses for PCLK, VSYNC and HSYNC. You could use an oscilloscope to figure out what the FT813Q is using though. \$\endgroup\$
    – sphanlung
    Commented May 16, 2019 at 18:55
  • \$\begingroup\$ Thank you for your help! \$\endgroup\$
    – cch
    Commented May 16, 2019 at 20:24
  • \$\begingroup\$ I am going to try it with a FPGA then. Here is another datasheet without the extra chip and just the LCD newhavendisplay.com/specs/NHD-3.5-320240MF-ASXN-CTP.pdf \$\endgroup\$
    – cch
    Commented May 16, 2019 at 20:26
  • \$\begingroup\$ I don't know if that contains the datasheet you were referring to. \$\endgroup\$
    – cch
    Commented May 16, 2019 at 20:26

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