I purchased a XIAO-ESP32-S3 with an expansion shield Grove-Shield-for-Seeeduino-XIAO-embedded-battery-management-chip and a ST7789 1.22" diplay (Grove 1.2-inch IPS Display | Seeed Studio Wiki)
1st problem:
The wiki entry from the display speaks of SPI, but in the image it shows I2C naming.
I don’t understand, like at all.
The datasheet is also extremely hard to understand, as it talks about the strangest interfaces.
What interface is used? As far as I can see there is only code for SPI displays for ST7789.
2nd problem:
As far as I understand (I only found SPI code only for ST7789) I need to connect MOSI from ESP32 to DTA display and SCK to SCK.
The is no connector on the expansion board that has D10 (MOSI) and D8 (SCK) on it for it to fit the provided seeedstudio connector.
See: files.seeedstudio.com/wiki/Grove-Shield-for-Seeeduino-XIAO/img/pinout.png
SPI Pins for the display:
MOSI (DTA) → “SDA” label on the display
SCK (Clock) → “SCL” label on the display
You will also need:
CS (Chip Select): Usually tied to a GPIO pin
DC (Data/Command): Another GPIO pin
RST (Reset): Optional but usually required for initialization
Yeah, that’s how I am used to it.
The problem is that a) there are no CS DC or RST pins available with this display board and b) the connector and the breakout board are not pin compatible with the display, so although they use the same molex seeedstudio connectors I cannot plug them together…
Guess have to cut and solder the display to the XIAO pinheader making the breakout board useless.
So yea, it is a Feature not a bug, also known as I2C in this case
Simplified Interface: The display adopts a serial SPI interface and only requires the SCK and SDA connections to the main controller. This greatly simplifies user operation and saves time on wiring.
There is plenty of example code here for this exact unit. use the search and you will find it I have one on here with the similar display, connected to the Expansion board.
No, use the Wire lib and the I2c pins.
All pins are available on expansion board BTW.
PJ 
