Bert Melis

How does your circuit look like? What parts do you use? I tested with - a (genuine) MAX3485 - 120 Ohm resistor on both ends of the RS485 wire -...

Can you swap A and B? on the MAX485 board? If I found the right circuit on the Internet, this board biases the A line to Vcc and the B...

See also http://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf Mind that your ESP uses UART and treats HIGH as binary 1 and LOW as binary 0. That's why the Serial needs to be "inverted". *If somebody...

Make sure you have this ```C++ #define MAX485_RE_NEG 4 #define Slave_ID 1 #define RX_PIN 16 #define TX_PIN 17 esp32ModbusRTU modbus(&Serial1, MAX485_RE_NEG); // in void setup() Serial1.begin(9600, SERIAL_8N1, RX_PIN, TX_PIN, true);...

What you can do is use `Serial` as Modbus interface, connect the board via USB to your computer and look in your terminal what the ESP is actually sending. The...

I'm not completely following... When you pass Serial instead of Serial1 to the modbus object, the modbus messages will show up on your terminal. You'll want to display them in...

You've connected the level converter wrong. high voltage is MAX485 side, low is ESP. The MAX485 should be powered with 5V, not 3.3V. You might as well fried your pins...

Strange. Maybe some task priority issues. I'll check things out. You can fiddle yourself if you alter the task priority directly in the code.

Just to be sure: how much time passes between sending the request and receiving the error? Should be about 5 secs.

I might spotted a but in the Arduino core. I'll try this evening.