This cookie is set by GDPR Cookie Consent plugin. The cookie is used to store the user consent for the cookies in the category 'Other. The cookies is used to store the user consent for the cookies in the category 'Necessary'. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category 'Functional'. The cookie is used to store the user consent for the cookies in the category 'Analytics'. These cookies ensure basic functionalities and security features of the website, anonymously. Res_dbl = modbus.Necessary cookies are absolutely essential for the website to function properly. String res = 'Temperature: ' + String(res_dbl) + ' C ' Uint8_t result = modbus.readInputRegisters(0x01, 2) ĭouble res_dbl = modbus.getResponseBuffer(0) / 10 Modbus.postTransmission(postTransmission) Callbacks allow us to configure the RS485 transceiver correctly Modbus communication runs at 9600 baud Arduino Digital Pin 2 = Rx/Tx 'Enable' High to Transmit, Low to ReceiveĭigitalWrite(MAX485_RE_NEG, HIGH) //Switch to transmit dataĭigitalWrite(MAX485_RE_NEG, LOW) //Switch to receive data #define MAX485_RE_NEG 4 //D4 RS485 has a enable/disable pin to transmit or receive data. The Data Enable (DE) and Receiver Enable (RE) pins are hooked up as follows:

Rx/Tx is hooked up to the hardware serial port at 'Serial'.

We're using a MAX485-compatible RS485 Transceiver. Thermal sensorĮSP32 program to work with RS485 board with DE/RE pins #include 'ModbusMaster.h' // RE (receiver enable) – enable receiver to work RO (receiver output) – receiver digital output ĭE (driver enable) – enable transmitter to work

ESP32 LuaNode32ĭI (driver input) – transmitter digital input Otherwise possible to burn out GPIO ESP32!!! Power supply for RS485 board MUST BE 3,3V, If you will use separate power supply for RS485 board it must be: In my example RS485 board is power supplied from the 3,3 V pin of the LuaNode32 board. The s chematic of connecting ESP32 LuaNode32 to the inexpensive RS485 module is next: Connection of ESP32 to inexpensive RS485 module So, on the most developers boards based on ESP32 U0UXD occupied by USB converter. If you don’t move U1UXD to other pins it may cause an error. Some boards are used this port on the pin occupied by SPI Flash.

U0UXD used by USB converter of the ESP32 DevKit V1.

Fritzing esp32