Hi,
I just spent the day being baffled by a strange RS-232 problem. I connected a barcode module which uses a MAX232A compatible RS-232 buffer from intersil. On my board uses a RS-232 buffer from Analog devices which has an enable pin for the receivers. The barcode module was sending data out without any problems when not connected to my board, but as soon as It was connected, I could get nothing on the scope. On the TTL side of the buffer the signal was visible, but on the RS-232 side nothing. After quite a few ours of frustration, I found that due to an etching problem on the PCB, the enable signal was at the wrong level, hence disabling the receivers. As soon as I enabled the receivers everything worked fine. It looks like the receivers, when disabled puts such a load on the other RS-232 output, that it kills the signal completely. Is this normal for RS-232 buffers ? Regards Anton Erasmus