Urgent help!

killingspring

Urgent help! [Copy link]

Dear experts, I designed a 485 isolation circuit, but now it cannot communicate normally. The waveform measured by the oscilloscope is there, I don't know why, please help me analyze it. Note: We bought someone else's Ethernet to 485 device, because the 485 it came out of is not isolated, I want to do an intrinsically safe design, so I add an isolation board outside.

dwh000

How to switch between sending and receiving

killingspring

dwh000 posted on 2018-1-4 11:58 How to switch the direction of sending and receiving

It doesn't matter what direction it is, it is bidirectionally isolated

chunyang

Both the receiving and sending and direction control must be isolated. You cannot just send and receive. Automatic reversing requires the sending signal to be reversed before driving the direction control pin. At the same time, the bus static bias must be added. Take a good look at the device manual of the 485 interface chip to understand the working logic and conditions.

bioger

Is there data before and after the quarantine? Let's take a look at the waveform.

killingspring

chunyang posted on 2018-1-4 13:11 Both the receiving and sending and direction control must be isolated. It cannot be done just for receiving and sending. For automatic reversing, the sending signal needs to be reversed before driving the direction control pin. At the same time, the bus static must be added...

Do you mean that the receiving and sending direction is controlled by the DE pin?

chunyang

killingspring posted on 2018-1-4 17:20 Do you mean that the transmit and receive direction is controlled by the DE pin?

The transmit and receive enable are controlled by two pins respectively. Please take a good look at the device manual.

killingspring

chunyang posted on 2018-1-4 17:28 The two pins control the transmit and receive enable respectively. Please read the device manual carefully.

Finally got it done. This is my first time to contact the 485 bus. I thought the transceiver would automatically switch between transmit and receive. I was too careless and made this joke.

chunyang

killingspring posted on 2018-1-5 18:37 Finally got it done. This is my first time using the 485 bus. I thought the transceiver would automatically switch between transceiver and receiver. I was too careless and made this joke

Reading the device manual carefully is a must for electronic engineers before designing. Moreover, the more experienced the experts are, the more carefully they will do such "simple" and "low-level" things. Have you read the device manuals for resistors, capacitors, and even wires? I have read them. Not only do I read them when I encounter a device I have never used before, but even when the method of use and conditions of use of a used device have changed, the first thing I do is still to read the device manual.

killingspring

chunyang posted on 2018-1-6 00:09 Reading the device manual carefully is a required course for electronic engineers before designing. Moreover, the more experienced the experts are, the more carefully they will do this kind of "simple" and "low-level" ...

I have learned a lesson