How to connect SPI MCU to multiple isolated SPI nodes?
Digital isolators such as ISO6441 and ISO6041 feature enable pins (ENx) which can be used to either enable or tri-state the respective outputs thereby allowing multiple output pins of multiple devices to be connected together. This enables an MCU with SPI interface to be connected to multiple other nodes with SPI interface while still maintaining isolation.
Additionally the following resources provide recommendations on how to calculate maximum SPI speed and device recommendations:
1. [FAQ] How to calculate the maximum SPI speed supported by a digital isolator?
Please refer to the below diagram that shows how an MCU with SPI interface can be connected to multiple nodes through digital isolators. The MCU uses select lines to enable only one digital isolator at a time thereby allowing data from only one SPI node to be read at any point of time.
