Two PCD8544 on Wemos D1 mini


I want to use two PCD8544s on one Wemos D1 mini. I couldn't find a tutorial for that specific problem - 2 SPI Displays.
As far as I understand I could adress one via Software SPI and one via Hardware SPI. The Clock would be the same for both as the Wemos only has 9 digital pins. But how do I adress them in software what library supports differentiating between two SPI displays?

Any direct help or helpful links will be appreciated :slight_smile:

Theoretically you can connect multiple slave devices to the same SPI bus (same SCK, MOSI and MISO connection), if you connect each CS (SS: slave select) to separate pins.
But I have not yet tried this with ESP8266 nor with other processors.
The SPI class usually supports multiple SPIs; they may be for the same bus with different SS pins, or different busses. And some SPI classes provide automatic slave selection for transfers with transaction handling. And the slaves need to be well behaved and release the bus when not selected.

Maybe my answer will trigger more answers with more detailed help, I hope.

I took a look at the ESP8266 SPI header file, which you can find there:


The CS or SS handling is per default not done by the SPI class, (setHwCs(false)), so you have control of the pin to use, this will be in the display class.

Yes, two SPI displays can share all lines except CS (chip select) line, which must be different (individual) for each display.