Rs485 is a popular communication standard used in industrial automation and IoT applications. It's a multi-point serial communication system that allows devices to communicate with each other over a single twisted pair cable.
The standard specifies a maximum cable length of 1200 meters for 24V systems and 500 meters for 5V systems. This is due to the signal degradation that occurs over long distances.
Rs485 is commonly used in applications where multiple devices need to be connected together, such as in industrial control systems, data acquisition systems, and sensor networks. It's also used in IoT applications where devices need to communicate with each other over long distances.
The standard supports data transfer rates of up to 1.5 Mbps and is widely supported by many microcontrollers and development boards.
What is RS485
RS485 is a form of serial communication that's faster and more versatile than its older brother RS232.
It can transmit not only device-to-device but also a communications bus to connect multiple devices at once, making it a game-changer in industrial control systems.
The maximum RS485 cable length is typically 1200 meters or about 4000 feet, giving you more flexibility in your setup.
You can connect up to 32 devices on one system, a vast improvement over RS232's limit of one device at a time.
RS485 doesn't have a standard connector, but you can still use a DB-9 connector or a terminal strip, making it easy to work with.
This protocol is less susceptible to noise issues, which can cause problems for electronics, and it allows for shielding of the cables to prevent noise.
RS485 is a widely used and very versatile form of serial communication, and its advantages make it a popular choice in industrial applications.
How it Works
RS485 is a serial communication standard that supports both full and half-duplex communication, making it a versatile choice for various industries. It's commonly used in noisy environments and longer bus lines due to its balanced signaling.
The RS485 standard features somewhat larger signal levels compared to TTL logic levels, which means electronic components with TTL signal levels need UART to RS485 signal converters, such as RS485 4 click. These converters are essential for allowing communication over the RS485 bus.
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The main active component of the RS485 4 click is the ADM2795E, an integrated dual channel RS485 driver/receiver with ICoupler isolation technology. This integrated circuit provides the required isolation level and features integrated galvanic isolation elements.
RS485 level signals are encoded into waveforms that energize primary windings of integrated transformers, which are then decoded back into their original values and routed to the UART pins with the appropriate TTL signal levels. This process effectively conducts digital signals through the isolation barrier.
The RS485 5 Click is based around the MAX485 transceiver, which draws between 120µA and 500µA of supply current when unloaded or fully loaded with disabled drivers. All parts operate from a single 5V supply, making it a convenient choice for many applications.
An RS-485 network can be configured in two ways: "two-wire" or "four-wire." In a "two-wire" network, the transmitter and receiver of each device are connected to a twisted pair, while in a "four-wire" network, one master port has the transmitter connected to each of the "slave" receivers on one twisted pair, and the "slave" transmitters are all connected to the "master" receiver on a second twisted pair.
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Here are some key differences between the two configurations:
- "Two-wire" networks have a delay between the end of a transmission and when the driver is tri-stated, which can be an important consideration for applications where multiple transmissions need to occur in rapid succession.
- "Four-wire" networks do not have this delay, making them a good choice for applications where multiple transmissions need to occur quickly.
In either configuration, devices are addressable, allowing each node to be communicated to independently. Only one device can drive the line at a time, so drivers must be put into a high-impedance mode (tri-state) when they are not in use. Some RS-485 hardware handles this automatically, while in other cases, the RS-485 device software must use a control line to handle the driver.
Pinout and Wiring
The pinout diagram for RS485 Click boards shows the correspondence between the pinout on the board and the pinout on the mikroBUS socket. The pinout is crucial for wiring the board correctly.
The table below shows the pinout for the RS485 4 Click board. Note that the pinout is the same for the RS485 5 Click board, with the exception of the Drive Output and Receiver Output pins.
The Power Supply pins are located on the mikroBUS socket, and the Ground pins are also easily accessible. Make sure to connect the power supply and ground pins correctly to ensure proper operation of the board.
Pinout Diagram
The pinout diagram is a crucial part of understanding how to connect and use a module. It shows how the pins on the module correspond to the pins on the mikroBUS socket.
The pinout diagram for the RS485 4 Click and RS485 5 Click modules is similar, but not identical. Both modules have a pin labeled "NC" (No Connection) on pin 1, which is not connected to anything.
The RS485 4 Click module has a pin labeled "Receiver Enable" on pin 2, which is used to enable the receiver. The RS485 5 Click module, on the other hand, has a pin labeled "Receiver Output" on pin 2, which is used to output the received data.
The power supply pins for both modules are located on pins 7 and 10. Pin 7 is labeled "3.3V" and provides a 3.3V power supply, while pin 10 is labeled "5V" and provides a 5V power supply.
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Here is a table summarizing the power supply pins for both modules:
The ground pins for both modules are located on pin 8 and are labeled "GND". There are also ground pins on pins 9 and 15, but they are not used for anything.
Two-Wire or Four-Wire?
When ordering your cable, keep in mind that "two-wire" is really two wires + ground, and "four-wire" is really four wires + ground.
Four-wire networks allow full-duplex operation, but are limited to master-slave situations where a "master" node requests information from individual "slave" nodes.
The slave nodes in a four-wire network cannot communicate with each other, which can be a limitation in certain applications.
Two-wire networks, on the other hand, are simpler and more cost-effective, but may not offer the same level of performance as four-wire networks.
Remember to consider the specific needs of your project when deciding between a two-wire or four-wire network.
Specifications
The RS485 module is a versatile and reliable choice for industrial applications. It can be used in harsh environments such as stage DMX lighting and remote controller lines.
There are two types of RS485 modules: the RS485 4 click and the Transceiver RS422/RS485. The RS485 4 click has a high voltage galvanic isolation of RS485 lines, allowing for high speed communication up to 2.5 Mbps. It also has compliance with EMI, ESD, and EDC protection regulations.
The Transceiver RS422/RS485 communication bus is compatible with UART interface and can be used for various automation systems, controllers, sensors, and small embedded devices that can share the same bus.
Here are the key specifications of the RS485 modules:
The RS485 4 click has a click board size of M (42.9 x 25.4 mm) and can operate with either 3.3V or 5V input voltage. The Transceiver RS422/RS485 has a click board size of S (28.6 x 25.4 mm) and can operate with 5V input voltage.
Product Details
The RS485 click board is designed for harsh industrial environments, making it suitable for applications such as stage DMX lighting and remote controller lines.
This click board features a high voltage galvanic isolation of RS485 lines, allowing for safe communication in environments with high voltage risks.
The on-board modules include the ADM2795E, an integrated dual channel RS485 driver/receiver with ICoupler isolation technology made by Analog Devices.
This click board provides high speed communication, up to 2.5 Mbps, and complies with EMI, ESD, and EDC protection regulations.
The interface of this click board is UART, making it compatible with a variety of microcontrollers.
It's worth noting that this click board does not have a ClickID feature.
The click board is compatible with the mikroBUS standard and has a size of M (42.9 x 25.4 mm).
The input voltage of this click board can be either 3.3V or 5V.
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Electrical Specifications
When working with RS485 communication, it's essential to consider the electrical specifications of the devices involved.
RS485 communication can be used in harsh industrial environments, such as in stage DMX lighting and Remote Controller lines.
The ADM2795E integrated dual channel RS485 driver/receiver provides high voltage galvanic isolation of RS485 lines, ensuring reliable communication.
The transceiver draw between 120µA and 500µA of supply current when unloaded or fully loaded with disabled drivers.
RS485 communication is compatible with UART interface, making it suitable for various automation systems and small embedded devices.
The MAX485 low-power transceiver for RS-485 and RS-485 communication is designed to be energy-efficient, drawing minimal power when in use.
Here are the electrical specifications of the devices mentioned:
RS485 communication is available in different sizes, including the M size (42.9 x 25.4 mm) and S size (28.6 x 25.4 mm).
Frequently Asked Questions
Is RS485 still used?
Yes, RS485 is still widely used in industrial equipment. Despite being older than Ethernet, it remains a popular choice for many industrial applications.
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