Hello
I bought 2 MAX485 to make a network between 2 micros as a test.
Before getting involved with micros I decided to test the Max using my laptop. So I brought usb to rs232 converter and I decided to make a test in the following manner:
1-To connect Tx to DI of the first max
2-To connect Rx to RO of the second max
3-To connect A & B of the maxs to gether.
Now the test is done if I send a serial data using terminal program on my labtop, then I receive its echo.
In other words, the sequence should be :
from tx rs232--->rs485--->to rs232 rx
I did the test and I was satisfied.
But I found something very strange later.
I discovered that I receive the echo on the terminal program even if there is no supply to maxs and there is no connection between A1-A2 and B1-B2 !!!!! (Look at the attached photo)
I thought there is short circuit somewhere, and I disassembled the whole circuit and reassembled it again, and I got the same result.
Is this normal ? if yes, then how I ensure that the echo is from the conversed rs485, not from the rs232 ? and if no, then what is wrong?
I bought 2 MAX485 to make a network between 2 micros as a test.
Before getting involved with micros I decided to test the Max using my laptop. So I brought usb to rs232 converter and I decided to make a test in the following manner:
1-To connect Tx to DI of the first max
2-To connect Rx to RO of the second max
3-To connect A & B of the maxs to gether.
Now the test is done if I send a serial data using terminal program on my labtop, then I receive its echo.
In other words, the sequence should be :
from tx rs232--->rs485--->to rs232 rx
I did the test and I was satisfied.
But I found something very strange later.
I discovered that I receive the echo on the terminal program even if there is no supply to maxs and there is no connection between A1-A2 and B1-B2 !!!!! (Look at the attached photo)
I thought there is short circuit somewhere, and I disassembled the whole circuit and reassembled it again, and I got the same result.
Is this normal ? if yes, then how I ensure that the echo is from the conversed rs485, not from the rs232 ? and if no, then what is wrong?
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