Hardware manual

16.9 "Cannot open /dev/ttyS?: Device or resource busy•
16.10 "Cannot open /dev/ttyS?: Permission denied"•
16.11 "Cannot open /dev/ttyS?"•
16.12 "Operation not supported by device" for ttyS?•
16.13 "Cannot create lockfile. Sorry"•
16.14 "Device /dev/ttyS? is locked."•
16.15 "/dev/tty? Device or resource busy"•
16.16 "Input/output error" from setserial, stty, pppd, etc.•
16.17 "LSR safety check engaged"•
16.18 Overrun errors on serial port•
16.19 Port gets characters only sporadically•
16.20 Troubleshooting Tools•
16.21 Almost all characters are wrong; Many missing or many extras•
17. Interrupt Problem Details
17.1 Types of interrupt problems•
17.2 Symptoms of Mis-set or Conflicting Interrupts•
17.3 Mis-set Interrupts•
17.4 Interrupt Conflicts•
17.5 Resolving Interrupt Problems•
18. What Are UARTs? How Do They Affect Performance?
18.1 Introduction to UARTS•
18.2 Two Types of UARTs•
18.3 FIFOs•
18.4 Why FIFO Buffers are Small•
18.5 UART Model Numbers•
19. Pinout and Signals
19.1 Pinout of 9-pin and 25-pin serial connectors•
19.2 Signals May Have No Fixed Meaning•
19.3 Cabling Between Serial Ports•
19.4 RTS/CTS and DTR/DSR Flow Control•
19.5 Preventing a Port From Opening•
20. Voltage Waveshapes
20.1 Voltage for a Bit•
20.2 Voltage Sequence for a Byte•
20.3 Parity Explained•
20.4 Forming a Byte (Framing)•
20.5 How "Asynchronous" is Synchronized•
Serial HOWTO
16. Troubleshooting 4