Is there any GPIO expander with galvanic isolation? I browsed a lot and couldnt find any GPIO expander with isolation.Thanks in advacne
You can use MCP23017(similar to MCP23S17 but not SPI) which is I2C based IOExpander. You need to isolate only 2 lines with a bidirectional isolator. For that you may use ADuM1251.
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You can use the usual shift register like the 74HC595, and use optocouplers for passing the data, clock, and latch signals. The LVT-847 is a quad optocoupler which costs less than a dollar in 1s at Digikey. Note that its speed is limited to less than 100 kHz.