I am using 89C51 to design a voltmeter that can be connected to PC through a RS-232. But the data sent back is not what I want and its format does not conform to the one I design.
Can someone tell where the faults possibly are?
Do you use the same baudrate, format (8N1, ... ?) on both sides?
Are you using a hardware usart in the µC? perhaps it needs a inverter, just like pic's do...
What does the controller send and how do you read it on your pc? you are aware that software like hyperterminal prints ASCII codes as their respective charachter? So if your controller sends 65 then hyperterminal will display 'A'...
The device which converts from serial to parallel, and from parallel to serial - they can be either hardware, or software. Many micro-controllers have them built it.