16F877 communication problem!

[liupengjian]

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.

 

[Nigel Goodwin]

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?

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

 

[liupengjian]

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

 

[Nigel Goodwin]

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

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