RS232 data output ----> RS232 micro controller

Oliver Lai · Joined: 12 Dec 2003 Posts: 16

Today I did some experiments, the system was set up as follow:

RS232 data output ---> PC COM2, received data, then from COM1 ------> RS232 micro controller, all with data baud rate 57600.
It works well! Data rate is not a problem.

When I connect RS232 data output -------> direct to RS232 micro controller, no any data have been received!

Any comment?
Thanks,
Oliver

Haplo · Joined: 06 Sep 2003 Posts: 659 Location: Sydney, Australia

What do you mean by 'direct to RS232 micro controller'? You are not using a RS232 driver chip (like MAX232) and implementing an inverted serial port on the PIC?
What does your '#use RS232' statement look like?

Oliver Lai · Joined: 12 Dec 2003 Posts: 16

The connect is:
unknow micro controller <-----> RS232 data output ------> RS232 (max232) <------> PIC18F452.

dbotkin · Joined: 08 Sep 2003 Posts: 197 Location: Omaha NE USA

May one safely assume you connected the two microcontrollers using a null modem cable? If not, that would explain it.

Oliver Lai · Joined: 12 Dec 2003 Posts: 16

dbotkin, you are right. I check the RS232 boards of the both sides, found the board of sending RS232, which get power supply from PC D-9 cable (PIN 4: DTR, PIN7: RTS, 10V), but can not get power if I connected with micro controller (just three wires).

I tried with addional power supply to PIN4 and PIN7 when I connected with three wire RS232. But the sending data is blocked, no more any data coming out.

Have somebody know how I can correct to add Voltage to the sending RS232 board?

Thanks in advance!

Oliver