16F877 communication problem!

Hi, every expert here,
I am doing a project which needs to use 16F877A to communicate with VB program running in my PC.
But I found it very strange that whenever I send some data from VB side to PIC , VB MScomm will receive a copy of it, ie, it seems that got echo.
so which side's problem is it? Does 877 have echo reponse to what it receives?

Thanks for your help.

liupengjian said:

Hi, every expert here,
I am doing a project which needs to use 16F877A to communicate with VB program running in my PC.
But I found it very strange that whenever I send some data from VB side to PIC , VB MScomm will receive a copy of it, ie, it seems that got echo.
so which side's problem is it? Does 877 have echo reponse to what it receives?

Click to expand...

Not as far as I know, are you sure your program isn't echoing it?.

Yes, I checked both sides' program.
In this communication I use a RS232 to RS485 converter, I dont know this will affect or not. I found that some converter will auto echo the sending data from RS232 port

liupengjian said:

Yes, I checked both sides' program.
In this communication I use a RS232 to RS485 converter, I dont know this will affect or not. I found that some converter will auto echo the sending data from RS232 port

Click to expand...

Try it without the converter, and see if it still echos.