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Figure 1. ST7735R 1.8" TFT colour LCD. Image source: eBay.

I have an ST7735R working on an Arduino Nano as shown below.

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Figure 2. Current setup.

I want to try mounting the display remotely (< 1 m) from the micro-controller.

  • I'll need separate wires for Vcc, GND, DIN (SDA) and CLK (SCK). That's four.
  • BL (backlight) can be wired locally.
  • I won't be using the SD card functionality.

Does anyone know if any of the RST, CS and D/C pins can be permanently grounded or connected to Vcc (via the 3.3 V / 5 V resistors) or are they required in boot or during operation? Any documentation I've read doesn't mention it and any pointers would save me some time figuring it out by trial and error.

Links:

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  • \$\begingroup\$ Seems like it would be simply to try those various ideas in your current setup. But I doubt they'd work. Why not put another cheap MCU at the display, and send a transmit-only serial stream over? If all else fails, read the data sheet ;-) \$\endgroup\$ Commented Aug 30, 2020 at 17:15
  • \$\begingroup\$ Thanks, @Chris. That was my original idea. I'm just trying to simplify it. \$\endgroup\$
    – Transistor
    Commented Aug 30, 2020 at 17:17
  • \$\begingroup\$ You certainly need D/C. It's used to indicate if the data on SDA is data (pixels) or a command. RST (reset) can probably be combined with power, e.g. a capacitor that charges slowly and resets the display after power up. CS (chip select) can probably be held selected if no other devices are connected to the same SPI bus. \$\endgroup\$
    – Codo
    Commented Aug 30, 2020 at 19:10

1 Answer 1

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According to the Adfruit 1.8" TFT display (which is an enhanced version of my display) documentation I can't reduce my cable to four wires.

This color display uses SPI to receive image data. That means you need at least 4 pins - clock, data in, tft cs and d/c. If you'd like to have SD card usage too, add another 2 pins - data out and card cs. However, there's a couple other pins you may want to use, lets go thru them all!

  • SCLK - this is the SPI clock input pin. Required.
  • MOSI (DIN / SDA) - this is the SPI Microcontroller Out Serial In pin, it is used to send data from the microcontroller to the SD. Required. card and/or TFT. Required.
  • Card CS - this is the SD card chip select, used if you want to read from the SD card. Not required and can be grounded.
  • D/C (Data Command) - this is the TFT SPI data or command selector pin. Required.
  • RST - this is the TFT reset pin. Connect to ground to reset the TFT! Its best to have this pin controlled by the library so the display is reset cleanly, but you can also connect it to the Arduino Reset pin, which works for most cases. Required but maybe possible to use a local RC delay.
  • Vcc - this is the power pin. Required.
  • GND Required.

As far as I can see I need a minimum of six wires between my micro and the display so I can't use an industrial M8 connector as I hoped.

I'll go with a local Nano at the display and this only requires VCC, GND and serial in.

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