@ichirow (1) I have also taken liberty to add a pin description to your question, so that (a) Other newbies can share your success/failure experience, and avoid reinventing new wheels, or frying more LCD modules! :) (b) Other ninjas can look at your pin description and suggest you how to troubleshoot, eg, (i) After initialization, how to use a multi-meter to measure the pin voltage levels (should RST High or Low, DC Hig or Low?)

(ii) When getting a blank screen, or picture too slow, how to use a multi-meter (Note 1) to measure the SPI signal pins (Should CS be very Low, CLK middle, ...? Note 1 - Of course rich guys should use a oscilloscope, but poor guys can use blinking LEDs, push buttons, multi-meter to also do the troubleshooting job effectively.

You asked what is the use what chip select signal CS0 and CS1. This is what I answered in the answer I referred. You need to wiki and google SPI to understand everything. But for my dual ST7789 LCD project, it is something like this. I am connecting two LCD modules to the same SPI0 bus, each module as the same SCLK, MOSI, MISO wires connected. The only difference is that module A CS pin is connected to SPI CS0 pin, and Module B's CS pin is connected to SPI CS1 pin.

Now if I set CS0 Low, and CS1 High, then Module A will be selected, and will talk to Rpi through SPI CLK, MOSI, MISO wires. At the same time, Module B is NOT selected, and will not respond to SPI signals.

Now the catch is this. For your 7 pin module, the LCD's CS wire is CONNECTED TO GROUND, therefore ALWAYS SELECTED, no matter Rpi's CS0, CS1 are High or Low, LCD does not care, always respond. So what I suggested to the OP of that question is suggesting him to extract the LCD's CS wire, DO NOT CONNECT TO GROUND, but connect to Rpi SPI CS1, then this modified LCD will be selected if Rpi SPI CS1 is low.

I have been trying to explain this to a coople of other user asking why they can not use two LCDs. But they don't try to understand what I am talking about, and gave up, ... :(

@tlfong01 I copy that. will do commander. check the broken or not.

@tlfong01 I never give up. Thank you for explain. I understood it. chipselect is sending signal for select the device. I going to try to again. I found good to wiring reference for 7pin device in japanese. He got the library and same probrem.

@ichirow Yes, it is a good idea to try out different alternatives before you finally decide how to start, and you can always change direction if you found you have made a wrong decision. About the st7789 python library, I found the Pimoroni one more promising, because it is NOT that AdaFruit oriented, or more compatible to Rpi. AdaFruit st7789 python libraries uses AdaFruit.GPIO, and microPython/circuitPython, which are not that compatible to Rpi.

I have not made my final decision which library to start. Perhaps you can google harder and see if there any better st7789 libraries than the two we are talking. Ha a nice day. See you tomorrow.