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 is also used in Digital Command Control (DCC) for model railways. In theatre and performance venues, RS-485 networks are used to control lighting and other systems using the DMX512 protocol. The EIA has officially disbanded and the standard is now maintained by the TIA as TIA-485, but engineers and applications guides continue to use the RS-485 designation. According to the EIA there is a maximum of 32 Unit Loads on one cable segment. The cable to be used is a shielded twisted pair (telephone type). RS485 is simpler because it uses only two wire (or a single pair) to carry out the data in bidirectional manner, using RS232, we need 3 wires at minimum to carry the data bidirectionally. With this boards, a CBL03 lines with RJ11 connectors can branch out to support an RS485 line consisting of three discrete wires. The two jacks are for RS485 cable in and RS485 cable out.

The two jacks are wired in parallel by circuit traces on the circuit board. These cables allow the dual RJ11 jacks of the RS485 option board of Laureate meters (digital interface ordering option 2) to be daisy chained and to be addressed digitally with no need for a hub. The solution is provided by the Laureate DIN rail mounted breakout board, which provides two RJ11 jacks with six screw clamp terminals all wired in parallel. This cable provides a USB type A connector for the PC end and an RJ11 connector for the meter end. RS485 uses two wires and sometimes a ground connection, so we used a twin-screen cable to go between the inverter to the EM112 Series Energy Meter and then onto the Raspberry Pi with a DB9 connector connected to the RS485 Pi board. It has an EM112 Series Energy Meter fitted in the same box to monitor energy production and consumption of the inverter. Our plans to upgrade our solar PV system this year are slowly progressing with installing a new Solis 1.5kW inverter and an EM112 Series Energy Meter, which have RS485 output and communicate using Modbus protocol. To minimise shadows over the top row of panels, we decided to mount 2 on the top row and 3 below, which will give us a theoretical maximum output of 1.6kW, which is suitable for the Solis Solar 1.5kW Mini 5G Inverter.

Especially when the transmission is carried over a long wire outdoor, the wires is potential to carry the dangerous signal like lightning or other high voltage induction. This is a method for connecting multiple RS485 devices with each other over a two-wire network. The diagram below shows potentials of the A (blue) and B (red) pins of an RS-485 line during transmission of one byte (0xD3, least significant bit first) of data using an asynchronous start-stop method. RS-485 does not define a communication protocol; merely an electrical interface. RS-485 only specifies the electrical characteristics of the generator and the receiver: the physical layer. Section 4 defines the electrical characteristics of the generator (transmitter or driver), receiver, transceiver, and system. A Unit Load is defined as a passive transmitter (in OFF-state) plus a receiver. A single analog input meter or transmitter can stream readings to a PC at up to 60 readings per second and the Custom ASCII protocol set to continuous (or streaming) model. Then use front panel programming to set the baud rate, protocol, digital address, half or full duplex, and other available parameters. A meter will a thermocouple input and set for Modbus RTU needs to set to full duplex even if the wiring and the receiving unit are for half duplex.

First set jumpers for your type of communications. To set up communications for your meter or counter, see the Serial Communications section of its user manual. RS485 is the preferred serial communications standard for long distance industrial communications. We installed a new Micro SD card with the latest Raspberry Pi OS, and after updating the software, the serial port and i2c bus were enabled. The data COM port on the base of the Solis inverter uses a small round 4-pin plug with a screw thread to hold it in place when connected. We then added the 10K pull-up and pull-down resistors to the RS485 Pi board and connected it directly to the Solis inverter. We found that there are 10K ohm resistors fitted on the A & B data lines with the A channel having a 10K pull-up resistor to 3.3 volts and the B channel having a 10K pull-down resistor to ground.