Unleash the true potential of your data network with SN65HVD31 and MK64FN1M0VDC12

RS485 3 Click is based on the SN65HVD31, a tristate differential line driver and differential input line receiver, from Texas Instruments. This click is intended to be used as a physical layer device, often referred to as PHY, providing physical interfacing of the MCU TTL level UART lines with the RS422/485 bus. It is well suited for transmitting smaller blocks of data over long distances, using two differential pairs, one for TX and other for RX line, allowing for full-duplex asynchronous communication. The SN65HVD31DR transceiver consists of a separate driver and receiver sections, which are always active upon powering the device. Driver section is used to drive the RS422/485 bus with the signal received on the UART RX line labeled as D on the IC, while the receiver section returns data from the bus back to the MCU via the UART TX line, labeled as R on the IC in the schematics. RS422/485 standard only specifies electrical characteristics of the transmitter and the receiver. It does not specify or recommend any communications protocol, only the physical layer. The top layer communication protocol of choice can be used, such as the MODBUS or DMX protocols. Therefore RS485 3 click offers UART RX and TX pins, routed to the appropriate mikroBUS™ TX and RX UART pins. These pins are used by the MCU to send data to the RS485, in a form determined by the used protocol. Please note that RS485 3 click supports only 3.3V MCUs and it is not

intended to be connected or controlled via the 5V MCU without a proper level shifting circuitry. The SN65HVD31DR IC allows communication with data rates up to 5 Mbps. However, the maximal transfer speed is determined by the bus length: longer bus lines will result in less transfer speed. The RS422/RS485 bus needs to be terminated with the resistor on both ends, which is equal to the characteristic impedance of the used cable, in order to prevent line reflections. The RS485 standard prescribes using a twisted pair cable as the data bus. Twisted pair cable tends to cancel common-mode noise and causes cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair. The RS-485 standard specifies that a compliant driver must be able to drive 32 unit loads (UL), where 1 unit load represents a load impedance of approximately 12 kΩ. Since the SN65HVD31 device is 1/8 UL, up to 256 such receivers can be supported by a single driver. When used as the master, the driver section of the RS485 3 click is always active. The same is true for the slave receivers on this same signal pair. In the case when slaves need to communicate back to the master, they are using another pair and the slave device drivers have to be intermittently enabled and disabled so that only one driver on a slave is enabled at a time. Since the SN65HVD31 device does not contain RE and

DE (Receiver Enable and Driver Enable) pins, slave driver cannot be disabled, resulting with bus contention, where the differential voltage can increase so that the resulting current can damage the IC. In that case, the driver current protection is activated, limiting this current to 250mA. Differential inputs contain internal Schmitt trigger circuits, preventing uncertain states of the pins. This ensures that the outputs are always in a defined state, also providing noise immunity. To further improve the signal integrity, RS485 3 click is equipped with two transient voltage suppression diodes (TVS diodes) used to protect the circuit from transients that can occur on the RS422/485 bus. There are two 2-pole screw terminals on board (RX+, Rx-, Tx+, Tx-) for connecting RS422/485 bus twisted pair cables, along with two screw terminals (GND) for common ground connection. The cables should be connected as close as possible to the termination resistors, preventing signal reflections in the parts of the signal cable that is not terminated by the resistor, so-called stubs. MikroElektronika provides a library that contains functions compatible with the MikroElektronika compilers, which can be used for working with the RS485 3 Click. The library also contains an example application, which demonstrates their use. This example application can be used as a reference for custom designs.

Clicker 2 for Kinetis is a compact starter development board that brings the flexibility of add-on Click boards™ to your favorite microcontroller, making it a perfect starter kit for implementing your ideas. It comes with an onboard 32-bit ARM Cortex-M4F microcontroller, the MK64FN1M0VDC12 from NXP Semiconductors, two mikroBUS™ sockets for Click board™ connectivity, a USB connector, LED indicators, buttons, a JTAG programmer connector, and two 26-pin headers for interfacing with external electronics. Its compact design with clear and easily recognizable silkscreen markings allows you to build gadgets with unique functionalities and

features quickly. Each part of the Clicker 2 for Kinetis development kit contains the components necessary for the most efficient operation of the same board. In addition to the possibility of choosing the Clicker 2 for Kinetis programming method, using a USB HID mikroBootloader or an external mikroProg connector for Kinetis programmer, the Clicker 2 board also includes a clean and regulated power supply module for the development kit. It provides two ways of board-powering; through the USB Micro-B cable, where onboard voltage regulators provide the appropriate voltage levels to each component on the board, or

using a Li-Polymer battery via an onboard battery connector. All communication methods that mikroBUS™ itself supports are on this board, including the well-established mikroBUS™ socket, reset button, and several user-configurable buttons and LED indicators. Clicker 2 for Kinetis is an integral part of the Mikroe ecosystem, allowing you to create a new application in minutes. Natively supported by Mikroe software tools, it covers many aspects of prototyping thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.