RS485 7 Click Board™

How Does The RS485 7 Click Board™ Work?

The RS485 7 Click Board™ is based on the THVD1424, a flexible RS-485 transceiver from Texas Instruments for asynchronous data transmissions. The THVD1424 has two termination resistors of nominal 120Ω, one across Y/Z and another across A/B. Both termination resistors are enabled or disabled using pins RET and TET pins of the mikroBUS™ socket, routed to the default positions of PWM and INT pins of the mikroBUS™ socket. Both termination resistors can be enabled or disabled, independent of the state of the driver or receiver. Termination is OFF if the device is unpowered or in thermal shutdown. Internal ESD protection circuits protect the transceiver against Electrostatic Discharges (ESD) according to IEC 61000-4-2 of up to ±8kV (Contact Discharge), ±15kV (Air Gap Discharge), and against electrical-fast-transients (EFT) according to IEC 61000-4-4 of up to ±4kV.

The THVD1424 RS-485 transceiver can be used in half-duplex or full-duplex RS-485 networks by populating an onboard R5 resistor. Full duplex mode is the default state of this board (with unpopulated R5 resistor), where Y and Z terminal pins are driver output pins, and A/B pins are receiver input pins. By populating the R5 resistor, Half duplex mode is activated where the driver and receiver share the same bus pins (Y/Z pins are both driver and receiver pins). The device state is then controlled via two mikroBUS™ pins labelled DE and RE (driver and receiver enable/disable), routed to the default positions of the AN and RST pins of the mikroBUS™ socket.

The THVD1424 can also be used in slow-speed or fast-speed RS485 networks by populating a slew rate control R10 resistor. By default, with the R10 resistor unpopulated, the maximum speed of operation for both driver and receiver is 20Mbps. By populating it, the maximum speed of operation for both driver and receiver is 500kbps, where the receiver path has an additional noise filtering feature enabled. The THVD1424 also has built-in protection features such as supply undervoltage, bus short-circuit, and thermal shutdown.

The RS485 7 Click Board™ can operate with either 3.3V or 5V logic voltage levels selected via the VIO SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, the main power supply of the RS485 transceiver can be selected between 3.3V or 5V voltage levels selected via the VCC SEL jumper. The wide common-mode voltage range and low input leakage on bus pins make this Click board™ suitable for multi-point applications over long cable runs. However, the Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used, as a reference, for further development.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout of the RS485 7 Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

ONBOARD SETTINGS AND INDICATORS

RS485 7 CLICK ELECTRICAL SPECIFICATIONS