RS4. 85 to RS2. 32 converter . Maximum length of the cable for RS2. For RS4. 85 it is about 1. In addition you can connect many devices to RS4. RS2. 32 — only 2). Send/receive mode is selected by RTS signal.

• RS232 is a asynchronous serial communication protocol widely used in computers and digital systems. It is called asynchronous because there is no separate.
• Introduction to Serial Communication Technical Tutorial 2002 – 12 - 06 Technical Tutorial Introduction to Serial Communication.

The converter was designed to be as simple as possible, so it has no some features that can be found in commercial grade products (e. MAX4. 85 converts TTL level signals to RS4.

Introduction to Communication Interface Parallel Communication Interface (PCI) Synchronous Asynchronous Serial Communication Interface (SCI) Data Transmission.

RTS line is used to change transmission mode of MAX4. RTS signal is first converted to TTL level by MAX2. DE and RE/ pins. 2 LEDs are used to indicate current state of the interface.

Duplex. If your control system needs to receiving and sending data in the same time you must use full duplex transmission mode. It is possible (and in real world this is the most popular case) that control system first sends request message and than waits for the response.

For this kind of systems half duplex communication is sufficient. This interface operates in half duplex mode at it only require 2 wires (full duplex 4 wires) and is simpler to build. Terminator. RS4. 85 bus must be terminated on the ends for long lines.

By default it is . If there are more then 2 devices on the bus, terminator is needed only on the first and last unit. Terminator can be omitted for short lines.

PCBSingle layered, size is 6. PCB artwork, the schematic and part list is available as PDF documents at the end of this article. Testing. After soldering all the elements, power the device. Red LED (LED2) should be bright.

Check voltage between pins 1. MAX2. 32 and between pins 5 & 8 of MAX4. It should be 5. V. Initial test. This test is just to prove that some parts of the converter works.

It needs only PC computer; another RS4. Connect your PC computer with converter using RS2.

Run Hyperterminal in Windows or any other terminal program, set 9. N1 and handshaking None. When you click hook on and hook off icons you should notice change in green LED. Click hook on icon and type anything in terminal window, the voltage between CON2- 1 and CON2- 2 should change quickly. Note You can use any other serial terminal program.

Real test. To see if converter works well some data must be properly sent and received. For the real test you need another device with RS4.

If you have two RS4. Just connect two interfaces, run 2 terminal programs and see if one terminal program can receive what you type in the other window. You must remember to switch appropriate send/receive mode for both interfaces (set appropriate state of RTS signal). When the converter is in TX mode and transmits data you can notice voltage change between A- B pins. Programming. From programmers point of view data transmission through RS4.

The only difference is that you have to set appropriate state of RTS line before sending/receiving any data. Because RTS line is very often used in half- duplex converters to switch TX/RX mode, many programs can be used without any modifications. Transmission modes of converter: RTS high – you can receive data. RTS low – you can send data.

For Win. 32 API (MS Windows) when you setup serial port set manual control of RTS line in DCB structure. Rts. Control=RTS.

RS- 2. 32, RS- 4. RS- 4. 85 Serial Communication General Concepts. This article explains the general concepts of the serial communication protocols RS- 2. RS- 4. 22, and RS- 4. What is Serial? The concept of serial communication is simple. The serial port sends and receives bytes of information one bit at a time. This is slower than parallel communication, which allows the transmission of an entire byte at once; however, it is simpler and can be used over longer distances.

For example, the IEEE 4. Typically, serial is used to transmit ASCII data. Communication is completed using 3 transmission lines: (1) Ground, (2) Transmit, and (3) Receive. Since serial is asynchronous, the port is able to transmit data on one line while receiving data on another.

This is referred to as Full- Duplex transmission. Other lines are available for handshaking, but are not required. The important serial characteristics are baud rate, data bits, stop bits, and parity.

For two ports to communicate, these parameters must match: Baud rate is a speed measurement for communication. It indicates the number of bit transfers per second. For example, 3. 00 baud is 3. When we refer to a clock cycle, in the context of serial, we mean the baud rate. For example, if the protocol calls for a 4.

Hz. This means that the serial port is sampling the data line at 4. Hz. Common baud rates for telephone lines are 1. Baud rates greater than these are possible, but these rates reduce the distance by which devices can be separated. These high baud rates are used for device communication where the devices are located near one another. Data bits are a measurement of the actual data bits in a transmission. When the computer sends a packet of information, the amount of actual data may not be a full 8 bits. Standard values for the data packets are 5, 7, and 8 bits.

Which setting you choose depends on what information you are transferring. For example, standard ASCII has values from 0 to 1. Extended ASCII uses 0 to 2. If the data being transferred is simple text (standard ASCII), then sending 7 bits of data per packet is sufficient for communication. A packet refers to a single byte transfer, including start/stop bits, data bits, and parity.

Since the number of actual bits depend on the protocol selected, the term packet is used to cover all instances. Stop bits are used to signal the end of communication for a single packet. Typical values are 1, 1. Since the data is clocked across the lines and each device has its own clock, it is possible for the two devices to become slightly out of sync. Therefore, the stop bits not only indicate the end of transmission but also give the computers some room for error in the clock speeds. The more bits that are used for stop bits, the greater the lenience in synchronizing the different clocks, but the slower the data transmission rate. Parity is a simple form of error checking that is used in serial communication.

There are four types of parity: even, odd, marked, and spaced. The option of using no parity is also available. For even and odd parity, the serial port will set the parity bit (the last bit after the data bits) to a value to ensure that the transmission has an even or odd number of logic high bits.

For example, if the data was 0. If the parity was odd, then the parity bit would be 1, resulting in 3 logic high bits. Marked and spaced parity does not actually check the data bits, but simply sets the parity bit high for marked parity or low for spaced parity. This allows the receiving device to know the state of a bit which enables the device to determine if noise is corrupting the data or if the transmitting and receiving devices' clocks are out of sync. Back to Top. 2. What is RS- 2. RS- 2. 32 (ANSI/EIA- 2.

Standard) is the serial connection historically found on IBM- compatible PCs. It is used for many purposes, such as connecting a mouse, printer, or modem, as well as industrial instrumentation.

Because of improvements in line drivers and cables, applications often increase the performance of RS- 2. RS- 2. 32 is limited to point- to- point connections between PC serial ports and devices.

RS- 2. 32 hardware can be used for serial communication up to distances of 5. Data. TXD (pin 3)Serial Data Output. RXD (pin 2)Serial Data Input. Handshake. RTS (pin 7)Request to Send.

CTS (pin 8)Clear to Send. DSR (pin 6)Data Set Ready.

DCD (pin 1)Data Carrier Detect. DTR (pin 4)Data Terminal Ready.

Ground. GND (pin 5)Ground. Other. RI (pin 9)Ring Indicator. Table 1: Pin Functions for RS- 2. Back to Top. 3. What is RS- 4. RS- 4. 22 (EIA RS- 4. A Standard) is the serial connection historically used on Apple Macintosh computers. RS- 4. 22 uses a differential electrical signal, as opposed to unbalanced signals referenced to ground with the RS- 2.

Differential transmission uses two lines each for transmit and receive signals which results in greater noise immunity and longer distances as compared to the RS- 2. These advantages make RS- 4. Back to Top. 4. What Is RS- 4. RS- 4. 85 (EIA- 4. Standard) is an improvement over RS- 4. With this enhanced multi- drop capability, you can create networks of devices connected to a single RS- 4. The noise immunity and multi- drop capability make RS- 4.

PC or other controller for data collection, HMI, or other operations. RS- 4. 85 is a superset of RS- 4.

RS- 4. 22 devices may be controlled by RS- 4. RS- 4. 85 hardware may be used for serial communication with up to 4. E Free Hotmail Inbox Email Microsoft.

Data. TXD+ (pin 8)Serial Data Output (differential)TXD- (pin 9)Serial Data Output(differential)RXD+ (pin 4)Serial Data Input(differential)RXD- (pin 5)Serial Data Input(differential)Handshake. RTS+ (pin 3)Request to Send (differential)RTS- (pin 7)Request to Send (differential)CTS+ (pin 2)Clear to Send (differential)CTS- (pin 6)Clear to Send (differential)DSR (pin 6)Data Set Ready. Ground. GND (pin 1)Ground. Table 2: Pin Functions for RS- 4. RS- 4. 22. Back to Top.

How do RS- 2. 32, RS- 4. RS- 4. 85 Compare? RS- 2. 32 is the most common serial interface and used to ship as a standard component on most Windows- compatible desktop computers. Now it is more common to use RS- 2. USB using a converter. RS- 2. 32 only allows for one transmitter and one receiver on each line.

RS- 2. 32 also uses a Full- Duplex transmission method. Some RS- 2. 32 boards sold by National Instruments support baud rates up to 1 Mbit/s, but most devices are limited to 1. RS- 4. 22 (EIA RS- 4.

A Standard) is the serial connection used on legacy Apple computers. It provides a mechanism for transmitting data up to 1. Mbits/s. RS- 4. 22 sends each signal using two wires to increase the maximum baud rate and cable length. RS- 4. 22 is also specified for multi- drop applications where only one transmitter is connected to, and transmits on, a bus of up to 1. RS- 4. 85 is a superset of RS- 4. RS- 4. 85 was made to address the multi- drop limitation of RS- 4.

Any of the slave devices on a RS- 4. Since RS- 4. 22 is a subset of RS- 4. RS- 4. 22 devices may be controlled by RS- 4. Both RS- 4. 85 and RS- 4. RS- 4. 85 allows up to 3. RS- 4. 22 has a limit of 1.

For both communication protocols, you should provide your own termination. All National Instruments RS- 4. RS- 4. 22 standards. The following table compares mode of operation, total number of drivers and receivers, maximum cable length, and maximum data rate. Specifications. RS- 2. RS- 4. 22. RS- 4.

Mode of Operation. Single- Ended. Differential. Differential. Number of Drivers / Receivers on One Line. Driver. 1 Receiver. Driver. 10 Receivers. Drivers*3. 2 Receivers.

Maximum Cable Length. F)4. 00. 0 ft. 40. Maximum Data Rate (at max cable length)1.

Mbit/s)1. 0 Mbit/s. Mbit/s. Table 3: Specifications of RS- 2. RS- 4. 22, and RS- 4. Only one driver is active at a time. Back to Top. 6. What is Handshaking? The method used by RS- 2.

TX, RX, and ground. For the data to be transmitted, both sides have to be clocking the data at the same baud rate.