1, if I understand correctly, the circuit is like this: 373-& gt；; Optocoupler->; Digital input end of single chip microcomputer. Because of the use of optical coupler, the single chip microcomputer must supply power separately. Other analog modules need 5v power supply and share the power supply with 373.

2. There is no need to add Schmidt shaping circuit.

3. Of course, the optical coupler has a direction, so it is necessary to identify the input and output. 5 1 digital output, which enters the input end of optical coupler (LED). When the input end of the single chip microcomputer, 373 is connected to the input end (LED) of the optical coupler, and the output end of the optical coupler is connected to the single chip microcomputer.

4. Because of their respective power supplies, 373 and MCU are not connected with each other. The ground of the input end (LED) of the optical coupler is connected to the ground of 373, and the ground of the output end of the optical coupler is connected to the ground of the single chip microcomputer.

If optocoupler isolation is used, the input and output of single chip microcomputer should be done, and a separate power supply can form a closed "isolation circle".

Supplement:

According to 373->; Optocoupler->; If the digital input terminal of single chip microcomputer is connected to ground or Vcc of 373 according to the effective level before optocoupler, or controlled.

If "sampling->; Digital input->; Optocoupler->; 373->； Single chip microcomputer "mode, 373 and single chip microcomputer * * *, using the Vcc of single chip microcomputer.