Index
- Cable wirings
- Serial communication conversion circuits
- Serial comminication isolation circuits
- Serial interface protection
- Serial interface application notes
- Logic signal level translations
- Transmission line interfacing
- Modulation, demodulation and coding
- Other circuits
Data communication circuits page
Cable wirings
Serial communication conversion circuits
- Circuit translates TTY current loop to RS-232C - provides signal translation between a passive current-loop (TTY) interface and a duplex RS-232C ports Rate this link
- Circuit translates TTY current loop to RS-232C - This circuit provides signal translation between a passive current-loop (TTY) interface and a duplex RS-232C port. Rate this link
- Current Loop Converter - Two Channel Isolated Industrial Version, schematic in pdf format Rate this link
- IC adds full-duplex RS-485 operation - simple RS-485 repeater provides full-duplex communications with only tow ICs Rate this link
- RS-232 to RS-422 conversion cable schematic - cable which can be used to connect computer RS-232 to some VCRs with RS-422 interface, zippled file packet Rate this link
- RS-232/485 converter has automatic flow control - RS-485 communications can provide longer range and better noise immunity than RS-232, as well as multidrop capability. Because it does not have separate transmit and receive lines, RS-485 requires flow control. RS-232/485 converters often use one of the RS-232 handshaking lines to control direction, but several communications-software packages do not support flow control. This circuit an RS-232/485 converter that uses the transmitted signal itself to control the flow. Rate this link
- RS-232 to RS-485 Isolated Converter - information on commercial product, datyasheet includes full circuit diagram Rate this link
- Two Channel, Port Powered RS-232 to RS-422 Converter - information on commercial product, datyasheet includes full circuit diagram Rate this link
Serial comminication isolation circuits
Galvanic isolation eliminates problems arising from disparate potentials between terminals.
- MAX1480 - optically isolated RS-485 IC from Maxim, datasheet in PDF format Rate this link
- RS-232C interface meets telecomminications safety specs - RS-232 isolation circuit Rate this link
- RS-232C circuit has galvanic isolation - - you can obtain longer transmission distances with the RS-232C interface if you use galvanic isolation between the two linked terminals Rate this link
- RS-232C circuit has galvanic isolation - You can obtain longer transmission distances with the RS-232C interface if you use galvanic isolation between the two linked terminals. Galvanic isolation also eliminates problems arising from disparate potentials between terminals. Using two MAX860/861 ICs and two TPL2200 optoisolators, you can obtain galvanic isolation for three-wire transmission without external supplies. Rate this link
- RS-232 to RS-232 Port-Powered Optical Isolator - brochure with schematic in pdf format Rate this link
- RS-485 to RS-485 Optical Isolator/Repeater Model 485OPB - The 485OPB can be used to optically isolate one piece of RS-485 equipment from the rest of an RS-485 system, or one local group of RS-485 equipment from another. It can also be used as an RS-485 repeater to expand an existing RS-485 system to greater than the 32 node limitation in the RS-485 Standard. Rate this link
Serial interface protection
Serial interface application notes
- RS-422/485 Application Note by B&B Electronics - contains lots of information Rate this link
Serial communication data generation and receiving
- Synchronizing controller detects baud rate - - A simple and inexpensive implementation using an eight-pin 12C508 controller (Microchip Technology, Chandler, AZ) provides both bit-rate detection and a synchronous, appended-clock output from an asynchronous input-data stream. Rate this link
- Use a PIC for automatic baud-rate detection - Automatic baud-rate detection is desirable in many applications. Microchip's (www.microchip.com) standard USART module that the company embeds in most of its PIC microcontrollers lends itself to a simple and easily implemented automatic baud-detection scheme. This example is designed for PIC18FXX2 in mind. Rate this link
- Use power line for baud-rate generation - One cost-saving measure associated with 8-bit embedded microcontrollers is to use a resistor-capacitor oscillator. These RC oscillators are inexpensive, but the trade-off is low stability with temperature and voltage. In these cases, you can find a low-frequency, stable clock source and use it to calibrate a baud-rate generator or event timer. One source of a low-frequency, stable clock is the line voltage. This voltage is a good source 50- or 60-Hz frequency that you can easily interface to the microcontroller's 16-bit timer. By counting CPU cycles for a half cycle of the external clock, you can determine the frequency of the microcontroller's internal RC oscillator and calibrate the baud rate. Rate this link
Logic signal level translations
- Circuit converts between TTL and shifted ECL Rate this link
- Logic Family Voltage Translation - how to translate between TTL, 74xx, CMOS, ECL, PECL, Low Voltage TTL, LVTTL, etc. Rate this link
- Two transistors form bidirectional level translator - illustrates a translation from 5 to 3V, but it can accommodate almost any other voltage levels, provided the logic-low levels are equal (usually 0V), translation from 1 to 100V are possible although slow. Rate this link
- Two-transistor circuit replaces IC - Linear Technology's recently introduced LTC4300 chip buffers I2C clock and data lines to and from a hot-swappable card. This task is difficult because the IC must work bidirectionally, meaning that you can simultaneously and actively drive both sides. However, as is sometimes the case, you can replace a complicated circuit by a simple one without much loss of performance. For example, transistors and resistors replace the entire IC. Two npn transistors, connected head-to-head, form the heart of the circuit. The two-transistor circuit offers the additional benefit of acting as a level translator between two logic levels, for example 3.3V and 5V. Rate this link
Transmission line interfacing
- Circuit adapts differential input to drive coax - uses an HFA1100 or HFA1105 to convert a balanced input signal to a single-ended output signal, uses positive feedback to characteristic-impedance matching while increasing the available output swing, as compared with using a simple series termination resistor Rate this link
- DC power wire also carries clock or data - high-side current-sense amplifier, IC1, offers a simple method of combining low-speed clocks or other signals with dc power in cables between subsystems Rate this link
- Emissions killers trap common-mode currents - unshielded twisted-pair cable that is transformer-coupled to a digital system can easily act as a radiating antenna because of common-mode currents induced by unwanted stray coupling from the digital portions of the system Rate this link
- Group-delay equalizer has gain more than 1 Rate this link
- Line driver economically synthesizes impedance - line-driver circuit uses a second op amp to synthesize the output impedance rather than inserting a power-hungry resistor in series with the op amp's output Rate this link
- RLC circuits match transmission lines to loads - you can use simple RLC circuits to compensate for the mismatch of high impedance CMOS input and transmission line Rate this link
- Speedy Spice subcircuit models lossy line - useful for simulating line driver designs Rate this link
Modulation, demodulation and coding
- Correlator works in presence of noise - clipped-signal correlator outperforms any resistor-capacitor clipped-signal correlator, and the circuit has no race paths Rate this link
- SP-L modulator uses single-speed bit clock - circuit for producing Manchester encoding modulation easily Other circuits Rate this link
Other circuits
- Synchronizing controller detects baud rate - a simple and inexpensive implementation using an eight-pin 12C508 controller (Microchip Technology, Chandler, AZ) provides both bit-rate detection and a synchronous, appended-clock output from an asynchronous input-data stream Rate this link
Related pages
- Local area networks Rate this link
- Telecommunications page Rate this link
- Telecommunications wiring page Rate this link
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