Share CS pin for SD and EHT on ESP32

Projects General Guidance
1

Is it possible to share CS pin ? I am using library:
Ethernet at version 3.3.5
Networking at version 3.3.5
FS at version 3.3.5
SD at version 3.3.5

I have a of SD connected and a W5500 EHT shield, like on the shield with SD and ETH for UNO/MEGA. I know one of the CS pin then have to be inverted.

It is working now with 2 pins, but i wold like to spare a pin.

Also, what is the reason for Enable?, it is not used on UNO/MEGA, but it needs to be defined in ESP32. I have set it to 0 in the sketch, and connected it to EN on ESP32, and it works fine.

2

in general you can share the SPI pins (MISO, MOSI, SCLK) between devices but separate CS (chip select) is required
if you are low on GPIO pins consider using a port expander, e.g. MCP23017

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3

Thanks, but I was just curious if it was an easy fix, to svare one pin.

4

If that are the only SPI devices, it could IN THEORY work, however I expect that the libraries are not prepared for this. Furthermore I also expect possible side effects as one of the two devices will be constantly selected and if the devices need different SPI settings e.g. phase of CLK than the selected device might see that as a first pulse.

In theory there is no difference between theory and practice, however in practice there is.

5

Thanks.

I am aware that one of the lib. Need a change and I need an inverter, but it is done on the w5100 shield :grinning_face:.