The a-line amplitude of RS485 communication cannot be maintained

1. Sending and receiving controllers:

During r25 welding, when R22 is suspended, the single chip microcomputer pin is separately controlled;

When r25 is suspended, R22 is controlled by the sending pin during welding;

 

2. When the upper and lower resistance of AB is not welded, the amplitude of line A in the output waveform remains high without waves.

A-line Waveform

3. The B-line level value is basically normal, but there is an alarm.

B-line Waveform

4. the waveform between AB is: And the overdrawn image is serious.

 

5. properly adjusted the uplink/downlink resistance to 2 K, which can basically communicate with each other. Previously, I thought it was a chip problem. I changed the film and the effect was the same. B was normal, the A amplitude does not go up. The 2 k waveform is as follows:

 

Basically, the baud rate is 115200, and the line length is 1.5 meters.