RS485 communication, must be A to A, B to B, not reverse connectionĢ.

In this way, the communication messages move on a single line in two opposite directions. The protocol uses a simplex connection on a single line. OverSampling = UART_OVERSAMPLING_16 if ( HAL_UART_Init ( &huart3 ) != HAL_OK ) ġ. Description English MODBUS ASCII/RTU is a master-slave communication protocol, able to support up to 247 slaves connected in a bus or a star network. (1) Initialize serial port 3, and turn on serial port to receive interrupt during initialization (2) Switch circuit: mainly to control the switch of sensor to reduce power consumptionįor single chip microcomputer, it is still serial communication, but RS232 level → RS485 level is realized through 485 chip. MODBUS ASCII/RTU is a master-slave communication protocol, able to support up to 247 slaves. RE and DE are transceiver enabled, 485 mode is selected: 3_ When sending data, the start bit (falling edge) of the data will be 3_ When the TXD pin level is pulled low, it will enable sending. (1) 485 circuit: because 485 is half duplex communication, it needs to control the transceiver, so it is simply designed as an automatic transceiver circuitĬonnect jumper cap W1 and W2 to use RS485 to send and receive, not to connect is common serial port transceiver. Circuit: according to the sensor properties, the circuit is mainly composed of two parts, communication circuit and power supply 4 LEDs connected to digital CH1-4 (blue) 2 push buttons connected to digital CH7-8. 4 LEDs connected to digital CH1-4 (yellow) 3 wires of RS485 Slave.

Sensor: hydraulic sensor, 12vDC, RS485 data output, Modbus protocol communicationĢ. Example of Modbus RTU communication between 2 IND.I/Os, Master and Slave This example has the following setup: Master.

Modbus rtu protocol example