Hello Folks,
I will share some of my experiences with mod-bus libraries test that I have done so far, kindly ask suggestion for a problem that I having right now with particle photon.
My intention is pulling some data from holding register on VFD Control techniques.
For some reason i dināt have success using this library,Smarmengol-Modbus Library, the problem I have no idea how to address a holding register like this one 401811, if i try to set 1811 register the arduino or photon
hangs and do nothing.
With this library ā4-20maā work fine with arduinoā¦ I use software serial to connect the MAX485, and that work perfect, I was able to read any register the VFDā¦ I tried that same library with the ESP8266 and works tooā¦ the problemā¦ if one disconnect the max485 from the ESP8266 or simple disconnect the cable from slave, the ESP8266 crash after a few intents of read the registersā¦timeoutsā¦
I tried to determine the problemā¦ but I am not so advanced programmer to dig into the library ā¦ so I gave up ā¦ I read somewhere thi is because the library Software Serial + mod-bus disable the GPIO pin interrupts very often . Now I move to try with Particle photon. initially I was having a problem very often got timeout while trying to read 10 holding registersā¦ mysteriously solved
for my test I just used the ā4-20maā library without any modification.
this is the sample code:
#include <ModbusMaster.h>
/*
We're using a MAX485-compatible RS485 Transceiver.
Rx/Tx is hooked up to the hardware serial port at 'Serial'.
The Data Enable and Receiver Enable pins are hooked up as follows:
*/
#define MAX485_DE A3
#define MAX485_RE_NEG A2
#define CT_VFD(m,n) (m *100+ n-1) // formula to acces VFD registers
// instantiate ModbusMaster object
ModbusMaster node;
#define reg_qty 11
void preTransmission()
{
digitalWrite(MAX485_RE_NEG, 1);
digitalWrite(MAX485_DE, 1);
}
void postTransmission()
{
digitalWrite(MAX485_RE_NEG, 0);
digitalWrite(MAX485_DE, 0);
}
void setup()
{
pinMode(MAX485_RE_NEG, OUTPUT);
pinMode(MAX485_DE, OUTPUT);
// Init in receive mode
digitalWrite(MAX485_RE_NEG, 0);
digitalWrite(MAX485_DE, 0);
// Modbus communication runs at 115200 baud
Serial.begin(19200);
Serial1.begin(19200);
// Modbus slave ID 1, Serial1 on the Particle Photon
node.begin(1, Serial1);
// Callbacks allow us to configure the RS485 transceiver correctly
node.preTransmission(preTransmission);
node.postTransmission(postTransmission);
}
bool state = true;
void loop()
{
uint8_t result;
uint16_t data[6];
// Toggle the coil at address 0x0002 (Manual Load Control)
//result = node.writeSingleCoil(0x0002, state);
//state = !state;
// Read 16 registers starting at 0x3100)
//result = node.readInputRegisters(0x3100, 16);
// read holding register VFD Control_techniques starting at Pr 1811 ( modbus 401811- 401814)
result=node.readHoldingRegisters(CT_VFD(18,11), reg_qty);
if (result == node.ku8MBSuccess)
{
Serial.println("Data: ");
// Serial.println(node.getResponseBuffer(1));
for (uint8_t j = 0; j < reg_qty; j++) Serial.println(node.getResponseBuffer(j),DEC);
Serial1.flush();
// node.clearTransmitBuffer();
}
else {
Serial.println("NO- RESPONSE"); // i got not response very oftem
//mySerial.flush();
}
//node.clearResponseBuffer();
// node.clearTransmitBuffer();
delay(5000);
Serial.println("running...");
}
Questions that I have so maybe some one can provide some advise
-The modbus master library ported by @peekay123 do not work for me . i got some errorsā¦ I see this library was ported 3 years agoā¦ so maybe that is the reasonā¦ Not clear if 4-20ma library specially ported for spark has any advantage over the un-ported 4-20ma master library.
-this is another diferent library Modbus_RS485 that seems pretty interestingā¦ but as is it right now I canāt get it to read any modbus registers on the VFD using photon not sure if i did right to addressee the register using this line -->telegram[1].u16RegAdd = 1811; // start address in slave
