Arduino IO Expansion V5 RS485 Problem

[tempUser]

Hello!
I bought this board and tested to work with RS485 port.
The data is successfully sent by the board, but it can not receive data!
The second pin is set to LOW (digitalWrite(2, LOW);).
I measured the voltage between the following contact of SP485 chip (see attached image):
- Vcc <-> GND = 5.14V
- DI <-> GND = 5.14V
- A <-> B = 1.8-2.5V (changes when receiving data)
- DE <-> GND = 0V
- RE <-> GND = 0V
- RO <-> GND = 0V

Why RO pin is zero and Serial.read() is nothing too?
Thank you very much!

Best regards,
Alexander

P.S. Datasheet of SP485: http://www.datasheetcatalog.org/datashe ... P481CN.pdf

[jack]

Hi there,
Could you provide us your wiring diagram to let us know about details?

Best regards
Jack

[tempUser]

Hi there,
Could you provide us your wiring diagram to let us know about details?

Best regards
Jack

I attached photo with connection. Thanks.

[jack]

I have tested the receiving and sending function with RS485 port on V5 IO shield,it works well.
Please kindly use the following demo code and checking your wiring.

RS485 Receiving:
- Vcc <-> GND = 3.28V
- DI <-> GND = 3.28V
- A <-> GND = 3.00V
- B <-> GND = 1.57V
- DE <-> GND = 0V
- RE <-> GND = 0V
- RO <-> GND = 3.28V


SAMPLE CODE
RS485 Transmit Data

Code: Select all

//RS485 has a enable/disable pin to transmit or receive data. 
//Arduino Digital Pin 2 = Rx/Tx 'Enable'; High to Transmit, Low to Receive
int EN = 2; 
 
void setup() 
{
  pinMode(EN, OUTPUT);
  Serial.begin(19200);
} 
 
void loop()
{
// send data 
  digitalWrite(EN, HIGH);//Enable data transmit
  Serial.print('A');
  delay(1000);
}

RS485 Receiving Data

Code: Select all

int ledPin = 13;// Light up Led when receiving data
int EN = 2;
int val;
 
void setup() 
{
  pinMode(ledPin, OUTPUT);
  pinMode(EN, OUTPUT);
  Serial.begin(19200);
}
 
void loop()
{
  // receive data
 digitalWrite(EN, LOW);//Enable Receiving Data
 val = Serial.read();
  if (-1 != val) {
    if ('A' == val) {
      digitalWrite(ledPin, HIGH);
      delay(500);
      digitalWrite(ledPin, LOW);
      delay(500);
    }
 }
}

[tempUser]

RS485 Receiving:
- Vcc <-> GND = 3.28V
- DI <-> GND = 3.28V
- A <-> GND = 3.00V
- B <-> GND = 1.57V
- DE <-> GND = 0V
- RE <-> GND = 0V
- RO <-> GND = 3.28V

I have the same results:
- Vcc <-> GND = 5.14V
- DI <-> GND = 5.14V
- A <-> B = 1.8-2.5V (changes when receiving data)
- DE <-> GND = 0V
- RE <-> GND = 0V
- RO <-> GND = 0V
except that:
- RO <-> GND = 0V

What does this mean? I think that it is not working properly SP485. What do you think about this?
Thanks!

[adolfainsley8]

What does this mean? I think that it is not working properly SP485. What do you think about this???