Although the maximum standard baud rate of the primary serial port is 19200 baud, nonstandard baud rates of over 80 Kbaud can be attained by the 68HC11's on-chip UART and the onboard RS232 driver. Using the primary Serial1 port is easy. On the other hand, the secondary serial port (Serial2) is implemented using hardware pins PA3 (input) and PA4 (output), and is controlled by the associated interrupts IC4/OC5 and OC4, respectively. To provide a convenient means of attaching two grounds to the serial cable, there are several pins (labeled GND) on the communications connector that are connected to the controller’s ground plane. Finally, if this means that enabling RS485 mode is not required in this configuration, can the FTDI cable be bypassed entirely by using Raspberry Pi's built-in UARTs combined with a chip like ZT485EEN? It provides a convenient means of connecting the QScreen Controller to a variety of peripheral devices, including analog to digital and digital to analog converters, real time clocks, and other computers which use high speed communication. Setting the MSTR bit initializes the QScreen as a master, and clearing the MSTR bit initializes it as a slave.

The QScreen Controller combines an embedded computer based on the 68HC11 microcontroller with a touch panel and LCD (liquid crystal display) graphic user interface (GUI) that is ideal for instrument control and automation. The RS-485 port is connected to the UART port on the Raspberry Pi using a SN65HVD72 interface. The RS-485 port on the RS485 Pi can be accessed through the male DB9 socket or the solder points on the PCB. The RS-485 port can be accessed through the DB9 port or the solder points on the PCB. The RS485 port can be accessed through the DB9 port or the solder points on the PCB. Before using the RS485 Pi you will need to solder both connectors onto the PCB. They are often terminated with 8 pin RJ45 connectors at either end. The symmetrical pin layout of the RJ11 sockets on the Unitronics PLCs allows an easy way of interconnecting the PLCs with both RS232 and RS485 communications.

The RS485 Pi is supplied with the 40 pin GPIO connector and the DB9 connector unsoldered. RS485 Pi at the top of the stack due to the height of the DB9 connector. The DB9 socket uses three wires as shown on the diagram below. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. The diagram below shows a typical network of RS-485 devices. A 120-Ω resistor is included with the RS485 Pi which will need to be fitted if the board is connected to the end of the RS-485 bus. This will be required if the RS485 Pi is used as an end node within an RS485 network. The recommended arrangement for connecting devices to an RS-485 network is to use a series on nodes connected along a line or bus with terminating resistors used at either end of the bus to reduce reflections. Unlike RS232, the RS-485 standard allows for multiple devices to be connected on the same network. RS485 is the preferred serial communications standard for long distance industrial communications. There are many different types of serial communication protocols like I2C and SPI which can be easily implemented with Arduino and today we are going to look at another most commonly used protocol called RS485 which is very commonly used in high noise industrial environments to transfer the data over a long distance.

The reason is that the serial RS232 protocol is, even its old, a very reliable, stable and solid communication protocol, which can easily be implemented with existing industrial equipment. If multiple analog input meters or transmitters are digitally addressed in command mode on an RS485 line using the Modbus RTU protocol or the Custom ASCII protocol, the rate becomes about 2 readings per second. It does not specify or recommend any data protocol. The RS485 Pi is a communication board supporting the RS-485 serial protocol. RS-485 standard conformant drivers provide a differential output of a minimum 1.5 V across a 54-Ω load, whereas standard conformant receivers detect a differential input down to 200 mV. Equipment using the RS-485 standard can be used over long distances in noisy environments. I'm trying to port a program, which communicates over RS485 half-duplex UART, to Raspberry Pi. As it is a half-duplex IC hence it cannot both transmit and receive at the same time. It does mean the library is harder to use. Modem to modem lines often use 1200, 4800, 9600, 14400, 28800, 33600, and 56000 baud. Before setting up the MODBUS connection, it's possible to set connection parameters (baud rate, etc) by assigning values to the minimalmodbus object.