In SX Microcontrollers, SX/B Compiler and SX-Key Tool, peterverkaik wrote:

Robert,

On my latest board, I use a dual 4x1 multiplexer CD4052 to share SPI and serial devices.
The X channel is used as input to read one of 4 outputs, the Y channel is used
as output to send a signal to one of 4 inputs. The Yn pins have all pullups, as has the X pin.
In addition, there are 1k series resistors in front of the X and Y pin (so Ron has little to no effect).
The two select inputs A and B are connected to my SDA and SCL lines.
This means, when I need to select a device, I must first lower SCL, then set SDA and SCL.
Before using the the I2C bus, I must set the Y pin high, because with I2C the channels are selected
 randomly, but due to the high Y, and the pulups on Yn pins, the devices consistently only see
a high input. This works very well.

regards peter

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