USB made simple: Part 3 - Data Flow Citat: "...At each end of the data link between host and device is a transceiver circuit. The transceivers are similar, differing mainly in the associated resistors...Each line can be driven low individually, or a differential data signal can be applied. The maximum 'high' level is 3.3V...When receiving, individual receivers on each line are able to detect single ended signals, so that the so-called Single Ended Zero (SE0) condition, where both lines are low, can be detected. There is also a differential receiver for reliable reception of data..."
Eksempel hvor besværlig det kan være: Understanding RS232 Serial Port Communication Citat: "...If RS232 is a standard why can't I just use a standard lead to connect together two RS232 ports and expect them to talk to one another? That's a good question...You've plugged your instrument into your computer's COM port, installed your data acquisition software, but no data appears. You suspect it is a problem with your RS232 communications. What do you do?...Obtain all the information available about your instrument or device. You will need to know the number of the com port into which you have plugged your device, the device baud rate, number of bits in the data byte and parity. Enter this information in ComDebug. If you have information about the Stop Bits then use it, otherwise set them to 2. This will at worse slow the message down slightly. See Making Measurements through the COM Port for a detailed explanation of each of these settings..."
