MKR 485 Shield don't get a receive from Piezo Motor Controller via RS485

Projects Networking, Protocols, and Devices
1

Hi,

I'm currently working on the following project:

I want to send and receive data to a Piezo driver via RS485.
For that purpose, I use this hardware:

The MKR 485 Shield is connected like that to the PMD401:

Y to Data+
Z to Data-
GND to GND

And jumper positions

  • FULL set to OFF
  • Z // Y set to ON

And here is my code:

#include <ArduinoRS485.h>

void setup() {
  RS485.begin(115200);
  Serial.begin(115200);
  RS485.receive();
}

int counter = 0;
byte rx_byte = 0;

void loop() {
  Serial.print("Count No: ");
  Serial.println(counter);
  RS485.beginTransmission();
  RS485.write("X1J20,0,150\r");
  RS485.write("X1E\r");
  Serial.flush();
  delay(500);
  while (RS485.available()) {
    // get a byte RS485
    rx_byte = RS485.read();
    // send the byte to the Monitor
    Serial.write(rx_byte);
  }
  RS485.endTransmission();
  Serial.println(" ");
  delay(10000);
  counter ++;
}

And the output from the terminal:

Count No: 1
X1J20,0,150X1E
Count No: 2
X1J20,0,150X1E 
Count No: 3
X1J20,0,150X1E

What I don't understand is the following:

If I send the command

RS485.write("X1J200,0,200\r");

The motor runs. -> so sending works, I think.

But if I send that command (like it is written in the manual page 2, point 7)

RS485.write("X1E\r");

I get no feedback at all. (like you see in the terminal)

So what do I have to do, that the Controller gives me feedback from the encoder? I tried a lot of different commands from the manual, but nothing works.... :frowning: It just reads the last sent commands.

2

You probably should read the response from the driver after the first command before you send the next command. Remember, RS-485 is (in most cases) a half-duplex connection. If you send the second command while the device sends you an answer it will be lost.

3

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