ST7789V and FT81x - startup

[moonie223]

Hello,

I am trying to use a ST7789 240x240 display with a FT810, but was wondering if I have the setup/startup sequence correct.

I believe the ST7789 needs commands written in serial mode before the RGB interface will work. I think there are three commands that are important, one to set the data width, one to select RGB format, and one to set the LCD RAM access to use the RGB input. (LCD registers RM, DM, and RIM)

I believe this is different than most LCDs, as most have the MIPI DPI interface enabled on startup, hx8357, as an example.

If I hook the ST7789 serial/SPI lines up to the MCU and send these commands before bringing the FT810 out of PD will it work as expected? Assuming I handle the reset of the LCD controller myself, the specific panel I would like to use does not have a DISP pin broken out.

Thank you!

[BRT Community]

Hi,

We have not tried this particular one but we have used a similar technique with the ILI9488 in our ME810A-HV35R displays. In that case we use the same lines for SCK/MOSI/MISO for the display and for EVE but we have a second chip select and a DCX line for command/data selection for the display.

You can get an example of the hardware in the ME810A-HV35R datasheet.
https://brtchip.com/wp-content/uploads/Support/Documentation/Datasheets/ICs/EVE/DS_ME810A_HV35R.pdf

We also have a draft of an example which configures it, if you would like a copy then please email us at support.emea@brtchip.com and we can send you a beta copy,

The actual commands and values needed over this interface may vary between displays but the manufacturer will often be able to recommend a command sequence to set it in RGB mode etc.

Best Regards, BRT Community

[moonie223]

Thank you for the reply.

ILI9488 is the other display I would like to try to use, I had not noticed it had a similar setup to enable RGB.

I believe I have all the correct commands to configure ST7789 for RGB, the datasheet covers it nicely. I will order a few test LCDs and breakout boards.

I guess my only remaining question is the use of the EVE DISP pin and the LCD reset pin. I notice on the ME810A-HV35R an OR gate is used, if I am not mistaken you would need to enable the FT81x, turn the DISP pin on, then reset the display and send the RGB commands via the host MCU?

Would there be any drawback to leaving the FT81x DISP pin float, and allowing the MCU to control the LCD reset independently?

[BRT Community]

Hi,

We have not used that configuration but we're not aware of any issue with using the MCU to do the reset so long as you provide the same sequence to reset the LCD controller on start-up. As you mentioned, we allow for both on the ME810A-HV35R via the OR gate. We normally leave the MCU input unused and use the DISP line from the FT810 when using this module but it should also work if using the MCU only. We're not sure about the timing needed for the ST7789 but you could even use a solder jumper in place of the OR gate to select one source or the other for initial testing.

Best Regards,
BRT Community