Hi
I have a Siemens MICROMASTER 420 variable frequency drive, I have seen that these use the USS protocol to communicate via RS485, I have tried to establish communication using an Arduino and a MAX485 module but for the moment I have not obtained any response from the MICROMASTER.
The connections are simple:
Arduino powered from the computer.
5V Arduino - > VCC from Max485
GND Arduino -> GND Max485
TX Arduino -> DI Max485
RX Arduino -> RO Max485
D2 Arduino -> DE/RE Max485
GND Arduino -> GND Micromaster 420
A Max485 -> Pin 15 Micromaster 420
B Max485 -> Pin 14 Micromaster 420
Test code:
const int ReDePin = 2; // HIGH = Driver / LOW = Receptor
byte command [] = { 0X02, //STX
0X0E, //LGE
0X00, //ADR
//PKW
0X12,0XBC, //PKE
0X00,0X00, //IND
0X00,0X00, //PWE1
0X00,0X00, //PWE2
//PZD
0X00,0X00,//STW
0X00,0X00, //HSW
0XA0 //BCC
};
void setup()
{
Serial.begin(9600,SERIAL_8E1);
Serial.setTimeout(100);
pinMode(ReDePin, OUTPUT);
}
void loop()
{
digitalWrite(ReDePin, HIGH);
Serial.write(command,sizeof(command));
Serial.flush();
delay(5000);
}
The test telegrams I have sent are:
byte command [] = {
0X02, //STX
0X0E, //LGE
0X00, //ADR
//PKW
0X12,0XBC, //PKE
0X00,0X00, //IND
0X00,0X00,0X00, //PWE1
0X00,0X00,0X00, //PWE2
0XA4//BCC
};
And:
byte command [] = { 0X02, //STX.
0X0E, //LGE
0X00, //ADR
//PKW
0X12,0XBC, //PKE
0X00,0X00, //IND
0X00,0X00,0X00, //PWE1
0X00,0X00,0X00, //PWE2
//PZD
0X00,0X00,//STW
0X00,0X00,0X00, //HSW
0XA0 //BCC
};
Whose PKW corresponds to the reading of the MICROMASTER parameter P0700 (Page 8, USS_protocol_en.pdf )
I see in the MICROMASTER that the number of rejected telegrams (parameter r2025 ) and the character frame errors (parameter r2026) is continuously increasing.
I think the problem may come with the telegram format as it is not clear to me if the PZD field should be included when reading a parameter and if so what values it should take.
If anyone can provide some information, thanks in advance.
Documentation:
USS protocol (uss_24178253_spec_76.pdf): https://support.industry.siemens.com/cs/document/24178253/specification-universal-serial-interface-protocol-uss-protocol?dti=0&lc=en-AO
USS Protocol with MICROMASTER M420 (USS_protocol_en.pdf): https://cache.industry.siemens.com/dl/files/889/5734889/att_848766/v1/USS_protocol_en.pdf
Related threads : Problem with USS protocol (Siemens protocol through RS485)
Best regards.