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SPI & I2C isolators

wizpic

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I'm currently looking and working on project where I need run 2 X MCP4822 (12Bit Dac) and 2 X MCP3422 (16Bit ADC) but need to have them isolated as there will be 2 identical channels which all run from there own supply. The main unit that will be sending the data will be an ESP32 running from 3.3V to both DAC'S and ADC'S.

The DAC's and the ADC's will need to be run from 5V's using 2 X Si8631BT-IS Silicon Labs, 3-Channel Digital Isolator (one for each channel ) and 2 X Bidirectional I2C Isolators.

I just want to make sure that it's ok to run one side from 3.3V and the other side from the +5V supply before I jump in feet first ?

I've attached a drawing to how I think it should be wired but only showing 1 channel as the other will be the same.
 

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KlausST

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Hi,

3.3V and 5.0V on the isolators is no problem.
But I'd replace the I2C and use an SPI ADC.

Klaus
 

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Thanks for the input which is good to know.
How many SPI devices can I place on the SPI lines on an Arduino ?
I know each device has got to have it's own CS pin, Only I'm using to ST7920 128X65 LCD already, Just in the process of now adding the MCP4822 DAC'S to my existing code
 

KlausST

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Hi,
How many SPI devices can I place on the SPI lines on an Arduino ?
There is no general answer. It is a question of drive current, load current, load capacitance, wire length, (expected) clock speed....

Klaus
 

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