Data communication circuits page
( 30 ) :
Cable wirings
Serial communication conversion
circuits
Serial communication isolation
circuits
Galvanic isolation eliminates problems arising from disparate
potentials between terminals.
Serial interface protection
Serial interface application
notes
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.
-
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.
-
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.
Logic signal level translations
-
Circuit converts between TTL and shifted ECL
-
Logic Family Voltage Translation - how to translate between
TTL, 74xx, CMOS, ECL, PECL, Low Voltage TTL, LVTTL, etc.
- Simple
RS-232 receiver - simple one transistor RS-232 level to TTL
level converter
-
TTL to RS-232 interfacing
-
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.
-
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.
Transmission line interfacing
Modulation, demodulation and
coding
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
back to :
Links >>
Electronic Circuits
|