help needed on actual modbusRTU implementation

[rzylius]

Dear Alexander,

I have a solar inverter with quite a specification:

The IMEON RS485 port is configured to use the following

• Baud rate : 9600
• Data bits per Byte : 8
• Parity : None
• Stop bits : 1
• Encoding: big endian(MSB LSB: value 0x
• CRC: little endian (LSB MSB: value 0x3412 is 0x1234)
• Slave address: 0x01
• Data message format: Hexadecimal
• The instant read values in the database are updated each 10 seconds.
• The set values are updated each 1 minute in database.
• Response timeout is 10 seconds.

I got connected and all works pretty ok out of the box. But I quite often I receive error (not consistently)

EX_TIMEOUT = 0xE4, // Custom. Operation not finished within reasonable time

I tried to play with #define MODBUSIP_TIMEOUT 1000 setting, without apparent improvement. maybe you may advise the logic how I should try to customize settings for it to work reliably?

Very much appreciate your work,

regards, Rimantas

[emelianov]

Hi,
Typically timeout errors is result of wiring problems. Probably flow control is required for transceiver used.

[rzylius]

Typically timeout errors is result of wiring problems.

I have controller 3 metres away from the inverter. and 50-70% of transactions do get good response. I thought this means wiring is ok? Or what should I check regarding the wiring?

Probably flow control is required for transceiver used.

Can you elaborate this? Should I use Serial (now I have softwareSerial for that)? Any specific settings you would avise to try?

Technical document of inverter specifies "Response timeout is 10 seconds.". This sounds to me like an exceptional setting, could that be a source of the problem that inverter may be "slow" in quite some cases and controller just timesout?

[emelianov]

Basing on you initial post I was suspecting some issue with RS485 transceiver. If most of transactions are ok that was wrong idea.
Still not clear about physical layer: if it's RS845 or Serial TTL ?
Anyway physical data transfer problems is most possible reason of loosing part of packets.
From other hand basing on such long timeout you may try to increase inter frame delay by overwriting setBaudrate(..) in Modbus.cpp to something like

void ModbusRTUTemplate::setBaudrate(uint32_t baud) {
    _t = 4; // play with the value
}

[rzylius]

Still not clear about physical layer: if it's RS845 or Serial TTL ?

RS845 in my case, I have esp8266 with max485.

I will try to replace the wire, adn will try to play with setBaudrate

[rzylius]

Dear Alexander,

I would very much appreciate your further advice. I tested read and write operations with inverter with my windows10/usbRS485 adapter and qModbusMaster. I do not have with this config much of the access to configuration, but 9800 baud rate / 8N1 / no flow control / 1sec timeout gives me very rare timeouts (like 5%).

on esp8266 I tried both Serial and softwareserial ports.
Your advised setBaudrate _t = 4 works best, but I get ~30-40% timeouts. other integer values more or less degrade performance.

#define MODBUSRTU_TIMEOUT 2000
decreasing this value lower than 1000 increases significantly timeouts. But further increases do not give better results,

Wiring I believe is not a problem, as other adapter on the same wiring works well.

I would very much appreciate your advice how should find out the problem or what settings I should try to test.

Thanks a lot.

[rzylius]

I tried with MODBUSrtU_DEBUG option, but not even sure where to start comprehending.

09:39:24.087 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:24.087 ->
09:39:24.087 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
09:39:24.087 ->
09:39:24.087 -> load 0x4010f000, len 3584, room 16
09:39:24.087 -> tail 0
09:39:24.087 -> chksum 0xb0
09:39:24.087 -> csum 0xb0
09:39:24.087 -> v2843a5ac
09:39:24.087 -> ~ld
09:39:25.234 -> 10 90 00 00 04 EC CA
09:39:25.234 -> 10 90 00 00 04 EC CA
09:39:27.259 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:27.259 ->
09:39:27.259 -> Exception (28):
09:39:27.259 -> epc1=0x4020e25b epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000
09:39:27.259 ->
09:39:27.259 -> >>>stack>>>
09:39:27.259 ->
09:39:27.259 -> ctx: cont
09:39:27.259 -> sp: 3ffffd60 end: 3fffffc0 offset: 0190
09:39:27.259 -> 3ffffef0: 0000010a 3ffef608 3ffef5a0 4020e295
09:39:27.259 -> 3fffff00: 00000003 00000c54 00000001 00000001
09:39:27.259 -> 3fffff10: 40201064 3ffefeac 402129f4 00000003
09:39:27.306 -> 3fffff20: 3ffef538 3ffef608 3ffef5a0 40202327
09:39:27.306 -> 3fffff30: 00000000 00000001 4b020c49 00000000
09:39:27.306 -> 3fffff40: 40201064 00000000 402129f4 402129dc
09:39:27.306 -> 3fffff50: 40201064 00000000 402129f4 402129dc
09:39:27.306 -> 3fffff60: 00000000 00000100 00000003 40210100
09:39:27.306 -> 3fffff70: 0000000b fe007465 40212a08 402011c4
09:39:27.306 -> 3fffff80: 3fff0b00 00000001 00000002 3ffefe4c
09:39:27.306 -> 3fffff90: 00000001 3ffef6f0 3ffef6f8 4020241e
09:39:27.306 -> 3fffffa0: 3fffdad0 00000000 3ffefe0c 40210ec0
09:39:27.306 -> 3fffffb0: feefeffe feefeffe 3ffe850c 401014b5
09:39:27.306 -> <<<stack<<<
09:39:27.306 ->
09:39:27.306 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:27.353 ->
09:39:27.353 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
09:39:27.353 ->
09:39:27.353 -> load 0x4010f000, len 3584, room 16
09:39:27.353 -> tail 0
09:39:27.353 -> chksum 0xb0
09:39:27.353 -> csum 0xb0
09:39:27.353 -> v2843a5ac
09:39:27.353 -> ~ld
09:39:32.191 -> 10 90 00 00 04 EC CA
09:39:32.191 -> 10 90 00 00 04 EC CA
09:39:34.216 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:34.216 ->
09:39:34.216 -> Exception (28):
09:39:34.216 -> epc1=0x4020e25b epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000
09:39:34.216 ->
09:39:34.216 -> >>>stack>>>
09:39:34.216 ->
09:39:34.216 -> ctx: cont
09:39:34.216 -> sp: 3ffffd60 end: 3fffffc0 offset: 0190
09:39:34.216 -> 3ffffef0: 0000010a 3ffef608 3ffef5a0 4020e295
09:39:34.264 -> 3fffff00: 00000003 00001ace 00000001 00000001
09:39:34.264 -> 3fffff10: 40201064 3ffefeac 402129f4 00000003
09:39:34.264 -> 3fffff20: 3ffef538 3ffef608 3ffef5a0 40202327
09:39:34.264 -> 3fffff30: 00000000 00000001 45604189 00000000
09:39:34.264 -> 3fffff40: 40201064 00000000 402129f4 402129dc
09:39:34.264 -> 3fffff50: 40201064 00000000 402129f4 402129dc
09:39:34.264 -> 3fffff60: 00000000 00000100 00000003 40210100
09:39:34.264 -> 3fffff70: 0000000b fe007465 40212a08 402011c4
09:39:34.264 -> 3fffff80: 3fff0b00 00000000 00000002 3ffefe4c
09:39:34.264 -> 3fffff90: 00000001 3ffef6f0 3ffef6f8 4020241e
09:39:34.264 -> 3fffffa0: 3fffdad0 00000000 3ffefe0c 40210ec0
09:39:34.310 -> 3fffffb0: feefeffe feefeffe 3ffe850c 401014b5
09:39:34.310 -> <<<stack<<<
09:39:34.310 ->
09:39:34.310 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:34.310 ->
09:39:34.310 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
09:39:34.310 ->
09:39:34.310 -> load 0x4010f000, len 3584, room 16
09:39:34.310 -> tail 0
09:39:34.310 -> chksum 0xb0
09:39:34.310 -> csum 0xb0
09:39:34.310 -> v2843a5ac
09:39:34.310 -> ~ld
09:39:39.299 -> 10 90 00 00 04 EC CA
09:39:39.299 -> 10 90 00 00 04 EC CA
09:39:41.323 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:41.323 ->
09:39:41.323 -> Exception (28):
09:39:41.323 -> epc1=0x4020e25b epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000
09:39:41.323 ->
09:39:41.323 -> >>>stack>>>
09:39:41.323 ->
09:39:41.323 -> ctx: cont
09:39:41.323 -> sp: 3ffffd60 end: 3fffffc0 offset: 0190
09:39:41.323 -> 3ffffef0: 0000010a 3ffef608 3ffef5a0 4020e295
09:39:41.323 -> 3fffff00: 00000003 00001b55 00000001 00000001
09:39:41.369 -> 3fffff10: 40201064 3ffefeac 402129f4 00000003
09:39:41.369 -> 3fffff20: 3ffef538 3ffef608 3ffef5a0 40202327
09:39:41.369 -> 3fffff30: 00000000 00000001 7e353f7c 00000000
09:39:41.369 -> 3fffff40: 40201064 00000000 402129f4 402129dc
09:39:41.369 -> 3fffff50: 40201064 00000000 402129f4 402129dc
09:39:41.369 -> 3fffff60: 00000000 00000100 00000003 40210100
09:39:41.369 -> 3fffff70: 0000000b fe007465 40212a08 402011c4
09:39:41.369 -> 3fffff80: 3fff0b00 00000001 00000002 3ffefe4c
09:39:41.369 -> 3fffff90: 00000001 3ffef6f0 3ffef6f8 4020241e
09:39:41.369 -> 3fffffa0: 3fffdad0 00000000 3ffefe0c 40210ec0
09:39:41.416 -> 3fffffb0: feefeffe feefeffe 3ffe850c 401014b5
09:39:41.416 -> <<<stack<<<
09:39:41.416 ->
09:39:41.416 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:41.416 ->
09:39:41.416 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
09:39:41.416 ->
09:39:41.416 -> load 0x4010f000, len 3584, room 16
09:39:41.416 -> tail 0
09:39:41.416 -> chksum 0xb0
09:39:41.416 -> csum 0xb0
09:39:41.416 -> v2843a5ac
09:39:41.416 -> ~ld
09:39:46.365 -> 10 90 00 00 04 EC CA
09:39:46.365 -> 10 90 00 00 04 EC CA
09:39:48.349 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:48.395 ->
09:39:48.395 -> Exception (28):
09:39:48.395 -> epc1=0x4020e25b epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000
09:39:48.395 ->
09:39:48.395 -> >>>stack>>>
09:39:48.395 ->
09:39:48.395 -> ctx: cont
09:39:48.395 -> sp: 3ffffd60 end: 3fffffc0 offset: 0190
09:39:48.395 -> 3ffffef0: 0000010a 3ffef608 3ffef5a0 4020e295
09:39:48.395 -> 3fffff00: 00000003 00001b1f 00000001 00000001
09:39:48.395 -> 3fffff10: 40201064 3ffefeac 402129f4 00000003
09:39:48.395 -> 3fffff20: 3ffef538 3ffef608 3ffef5a0 40202327
09:39:48.395 -> 3fffff30: 00000000 00000001 4624dd2f 00000000
09:39:48.395 -> 3fffff40: 40201064 00000000 402129f4 402129dc
09:39:48.395 -> 3fffff50: 40201064 00000000 402129f4 402129dc
09:39:48.442 -> 3fffff60: 00000000 00000100 00000003 40210100
09:39:48.442 -> 3fffff70: 0000000b fe007465 40212a08 402011c4
09:39:48.442 -> 3fffff80: 3fff0b00 00000000 00000002 3ffefe4c
09:39:48.442 -> 3fffff90: 00000001 3ffef6f0 3ffef6f8 4020241e
09:39:48.442 -> 3fffffa0: 3fffdad0 00000000 3ffefe0c 40210ec0
09:39:48.442 -> 3fffffb0: feefeffe feefeffe 3ffe850c 401014b5
09:39:48.442 -> <<<stack<<<
09:39:48.442 ->
09:39:48.442 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
09:39:48.489 ->
09:39:48.489 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
09:39:48.489 ->
09:39:48.489 -> load 0x4010f000, len 3584, room 16
09:39:48.489 -> tail 0
09:39:48.489 -> chksum 0xb0
09:39:48.489 -> csum 0xb0
09:39:48.489 -> v2843a5ac
09:39:48.489 -> ~ld

[emelianov]

Can you provide complete code as it hard to say what is going wrong.

As for lost packets. I suspect that you are using RS485 modules with auto RX/TX switching. With such modules a have in my lab I was unable to get baud rate above 9600 form ESP side. From other hand the same module was working at least at 115200. So I suggest to replace RS485 transceiver.

[rzylius]

I use max485 with rx/tx control pin. I tested several IC's, the resuls does not seem to differ. I will post the code. very much appreciate your help

[rzylius]

Dear @emelianov ,

this is my code:

#define SLAVE_ID 1
const char* ssid = "************";
const char* password = "*******************";
#define HOST_NAME "ESP IMEON bridge"
#define ID_DEVICE 1
#define ID_GW 5
int16_t r26 = 0;
int16_t r50 = 0;
float countSuccess = 0;
float countError = 0;
//Used Pins
const int getPIN = D5; 
const int setPIN = D6;


//////// Libraries
#if defined ESP8266 // Includes of ESP8266
  #include <ESP8266WiFi.h>
    #ifdef USE_MDNS
    #include <DNSServer.h>
    #include <ESP8266mDNS.h>
  #endif
#elif defined ESP32 // Includes of ESP32
  #include <WiFi.h>
  #ifdef USE_MDNS
    #include <DNSServer.h>
    #include "ESPmDNS.h"
  #endif
#endif // ESP


// Time
uint32_t mLastTime = 0;
uint32_t mTimeSeconds = 0;
#include <ModbusRTU.h>
#include <ModbusIP_ESP8266.h>

//SOFTWARE SERIAL
#include "SoftwareSerial.h"
SoftwareSerial swSerial;

//Modbus objects
ModbusIP mb;
ModbusRTU mb_device;
ModbusRTU mb_gw;

void  getLED () {
  digitalWrite(getPIN, HIGH);
  delay(4);
  digitalWrite(getPIN, LOW);
}

void  setLED () {
  digitalWrite(setPIN, HIGH);
  delay(4);
  digitalWrite(setPIN, LOW);
}

uint16_t cbHregGet(TRegister* reg, uint16_t val) {
  getLED();
  return val;
}

uint16_t cbHregSet(TRegister* reg, uint16_t val) {
  setLED();
  return val;
}

bool cbConn(IPAddress ip) {
  Serial.print("connection from ");
  Serial.println(ip);
  return true; // Return 'true' to allow connection or 'false' to drop connection
}

bool cb(Modbus::ResultCode event, uint16_t transactionId, void* data) { // Callback to monitor errors
  switch (event) {
      case 0x00:
        countSuccess++;
        Serial.println("Transaction success");
        break;
      case 0x01:
        countError++;
        Serial.println("Transaction error: EX_ILLEGAL_FUNCTION, Function Code not Supported");
        break;
      case 0xE1:
        countError++;
        Serial.println("Transaction error: EX_GENERAL_FAILURE, Unexpected master error");
        break;
      case 0xE2:
        countError++;
        Serial.println("Transaction error: EX_DATA_MISMACH, Inpud data size mismach");
        break;
      case 0xE3:
        countError++;
        Serial.println("Transaction error: EX_UNEXPECTED_RESPONSE, Returned result doesn't mach transaction");
        break;
      case 0xE4:
        countError++;
        Serial.println("Transaction error: EX_TIMEOUT, Operation not finished within reasonable time");
        break;        
      default:
        countError++;
        Serial.print("Error while pulling from slave: ");
        Serial.println(event, HEX);
        break;
  }
  return true;
}

void readSlave(int16_t FIRST_REG, int16_t REG_COUNT) {
  Serial.print("Read slave, Hreg: 0x");
  Serial.println(FIRST_REG, HEX);
  if (!mb_device.slave()) {    // Check if no transaction in progress
    mb_device.pullHreg(SLAVE_ID, FIRST_REG, FIRST_REG, REG_COUNT, cb); 
    while(mb_device.slave()) { // Check if transaction is active
      mb_device.task();
      delay(10);
   }
 }
}

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);     
  pinMode(setPIN, OUTPUT);     
  pinMode(getPIN, OUTPUT);     
 
  // WiFi connection
    WiFi.begin(ssid, password);
    // Wait for connection
    while (WiFi.status() != WL_CONNECTED) {
      delay(500);
    }
  // Register host name in WiFi and mDNS
    String hostNameWifi = HOST_NAME;
    hostNameWifi.concat(".local");
    #ifdef ESP8266 // Only for it
        WiFi.hostname(hostNameWifi);
    #endif

Serial.begin(115200); 

//setup modbus RTU
  swSerial.begin(9600, SWSERIAL_8N1, D1, D2, false);
  mb_device.begin(&swSerial, D0); 
  
  mb_device.master();
//setup modbus TCP
  mb.server();
  mb.onConnect(cbConn); // Add callback on connection event

// READ ONLY IMEON REGISTERS
  mb.addHreg(0x0100, 0, 30);
  mb.addHreg(0x0200, 0, 21);
  mb.addHreg(0x0300, 0, 4);
  mb.addHreg(0x0400, 0, 16);
  mb.addHreg(0x0500, 0, 6);
  mb.addHreg(0x0600, 0, 3);

  mb.onGetHreg(0x0100, cbHregGet, 1500);
  mb.onSetHreg(0x0100, cbHregSet, 1500);
}
 
void loop() {
    // Each second
    if ((millis() - mLastTime) >= 1000) {
        Serial.println("");
        Serial.print("Transaction status: ");
        Serial.println(countError / (countError + countSuccess));
        mLastTime = millis();
        mTimeSeconds++;
        digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
        switch (mTimeSeconds % 10) {
          case 1:
            readSlave (0x0100, 11);
            break;
          case 2:
            readSlave (0x0300, 4);
            break;
          case 3:
            readSlave (0x0400, 4);
            break;
          case 4:
            readSlave (0x040A, 6);
            break;
          case 5:
            readSlave (0x0503, 6);
            break;
          case 6:
            readSlave (0x0600, 3);
            break;
          case 7:
            readSlave (0x0117, 7);
            break;
          case 8:
            readSlave (0x1000, 1);
            break;
          case 9:
            break;
          case 0:
            break;
        }
     }
    mb.task();
    mb_device.task();
    yield();
}

[emelianov]

Hello,
Can see nothing critically wrong with the code.
Suggestions are:

1. to use HardwareSerial for Modbus.
2. It's just small improvements

void readSlave(int16_t FIRST_REG, int16_t REG_COUNT) {
  Serial.print("Read slave, Hreg: 0x");
  Serial.println(FIRST_REG, HEX);
  if (!mb_device.slave()) {    // Check if no transaction in progress
    mb_device.pullHreg(SLAVE_ID, FIRST_REG, FIRST_REG, REG_COUNT, cb); 
    while(mb_device.slave()) { // Check if transaction is active
      mb_device.task();
      mb.task(); // Should process incoming requests if long time response of timeout on mb_device happens
      delay(10);
   }
 }
}

3. Just random thought: mb.onGetHreg(0x0100, cbHregGet, 1500); It's a bit wild but working way to add callbacks to all already defined registers ;).

[DOSpt]

Hi @rzylius

Do you have a terminator resistor (typically 120ohm)?
If not you might be having problems with the physical signal that would explain why at a different baud rate the results are different. Have you measured the signal with an oscilloscope just to have a better understanding of what is happening? I wouldn't look at the code before making sure that the signal integrity is OK. Anyway, make sure you have an 120ohm resistor in parallel with the differential signals on the master side.

Other thing that might be causing this is if there is a delay on the pins that control the direction of the transceiver. If there is to much capacitance on this pin there is the risk that it can be slow enough that when one of the sides starts transmitting it is still in the wrong mode. Again, the best thing to do is to measure the signals to be sure.

[rzylius]

Hi @DOSpt ,

thanks for the ideas. Indeed, I had max485 module connected directly without any resistors etc.

Now I used https://www.anodas.lt/en/max485-ttl-to-rs485-converter-module module, which improved the error rate. I hoped that would kill all the problems you advised on - resistor, capacitance, etc. Still, I get about ~20-25% errors consistently.

I will try to do measurements with oscilloscope. (well, and I guess I will come back with my measurements :)

[emelianov]

why at a different baud rate the results are different.

Prtobably because of SoftwareSerial. Serial data output formed by software is not so stable-in-time as hardware one.

Other thing that might be causing this is if there is a delay on the pins that control the direction of the transceiver. If there is to much capacitance on this pin there is the risk that it can be slow enough that when one of the sides starts transmitting it is still in the wrong mode. Again, the best thing to do is to measure the signals to be sure.

It should not be a problem as according to Modbus specification remode must send responce with delay that long enough to eliminate electrical processes affects.