Timeout error (0xE4) when requesting more than 28 registers.

[flintstones3000]

First of all thanks for developing this library. It has been working great on my ESP8266. I've come across an issue when requesting a read of more than 28 registers returns a timeout error message (0xE4). I've tried increasing #define MODBUSRTU_TIMEOUT 10000 in ModbusSetting.h but still no luck. Am I doing something wrong?

In my code below I'm requesting 30 registers:
`/*
*/

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>
#include <StreamString.h>
#include <SoftwareSerial.h>
#include <ModbusRTU.h>

#ifndef STASSID
#define STASSID "SSID"
#define STAPSK "PSK"
#endif

#if defined(ESP8266)
#define D8 (15)
#define D5 (14)
#define D7 (13)
#define D6 (12)
#endif

const byte Start_Reg = 1;
const char *ssid = STASSID;
const char *password = STAPSK;
const int UnitID = 2;
const int led = 13;

long int Val_SerialNumber = 0;

uint16_t holdingRegisters[62];
unsigned long combined = 0; // clear it out
float power = 0;
union equiv {
float x;
unsigned long l;
} equiv ;

ESP8266WebServer server(80);
SoftwareSerial S(D5, D6);
ModbusRTU mb;

bool cb(Modbus::ResultCode event, uint16_t transactionId, void* data) {

equiv.l = ((long)holdingRegisters[0] << 16) | (holdingRegisters[1]);
Val_SerialNumber = equiv.l;
Serial.println(Val_SerialNumber);

if (event != Modbus::EX_SUCCESS) {
Serial.print("Request result: 0x");
Serial.print(event, HEX);
}
return true;
}

void handleRoot() {
digitalWrite(led, 1);

mb.readHreg(UnitID, Start_Reg, &holdingRegisters[0], 30, cb);
while(mb.slave()){
mb.task();
delay(10);
}

digitalWrite(led, 0);
}

void handleNotFound() {
digitalWrite(led, 1);
String message = "File Not Found\n\n";
message += "URI: ";
message += server.uri();
message += "\nMethod: ";
message += (server.method() == HTTP_GET) ? "GET" : "POST";
message += "\nArguments: ";
message += server.args();
message += "\n";

for (uint8_t i = 0; i < server.args(); i++) { message += " " + server.argName(i) + ": " + server.arg(i) + "\n"; }

server.send(404, "text/plain", message);
digitalWrite(led, 0);
}

void setup(void) {
pinMode(led, OUTPUT);
digitalWrite(led, 0);
Serial.begin(115200);
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
Serial.println("");

S.begin(9600, SWSERIAL_8N1);
mb.begin(&S, D7); //RE Pin
mb.master();

// Wait for connection
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}

Serial.println("");
Serial.print("Connected to ");
Serial.println(ssid);
Serial.print("IP address: ");
Serial.println(WiFi.localIP());

if (MDNS.begin("esp8266")) { Serial.println("MDNS responder started"); }

server.on("/", handleRoot);
server.onNotFound(handleNotFound);
server.begin();
Serial.println("HTTP server started");
}

void loop(void) {
server.handleClient();
MDNS.update();
}`

[emelianov]

Try to play with SoftwareSerial library versions.
Also you can try to change power source for the board,