Custom code to make BSB-LAN accessible via Modbus

BSB_LAN/custom_functions/Modbus_Interface/BSB_LAN_custom.h

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+// Only doing Modbus maintenance work during loop
+mb.task();

BSB_LAN/custom_functions/Modbus_Interface/BSB_LAN_custom_global.h

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+/*
+ * These three scripts need to be copied to the main directory and the CUSTOM_COMMANDS definement needs to be activated in order
+ * to start a Modbus server that will relay queries from Modbus to the heating system and return the requested parameter values.
+ * Writing parameters is also possible.
+ * You need to define the parameters that should be allowed to be queried via the mb.addHreg function in BSB_LAN_custom_setup.h
+ * Since querying/setting parameters from/to the heating system may take up to two seconds, make sure that the Modbus client does not
+ * exit prematurely due to a timeout.
+*/
+
+#include "src/modbus-esp8266/src/ModbusTCP.h"
+ModbusTCP mb;
+
+// Remove this function when using Modbus RTU (over serial/RS485)
+bool cbConn(IPAddress ip) {     
+  Serial.print(PSTR("Modbus connection from IP: "));
+  Serial.println(ip);
+  return true;  // return false for example to prevent forbidden IP ranges
+}
+
+// Callback for querying a parameter - value will be queried from heating system and returned to Modbus client
+// This function only supports integers up to 16 bit unsigned.
+// Any other values will require further encoding into Modbus' 16 bit unsigned integers to whatever necessary value here!
+uint16_t cbGet(TRegister* reg, uint16_t val) {
+  uint16_t param = reg->address.address;
+  query(param);
+  if (decodedTelegram.prognr < 0) return 65535;
+  val = strtod(decodedTelegram.value, NULL);
+  return val;
+}
+
+// Callback for setting a parameter - value received will be sent to the heating system
+// This function only supports integers up to 16 bit unsigned.
+// Any other values will require further decoding from Modbus' 16 bit unsigned integers to whatever necessary value here!
+uint16_t cbSet(TRegister* reg, uint16_t val) {
+  uint16_t param = reg->address.address;
+  char val_as_char[20];
+  sprintf(val_as_char, "%d", val);
+  set(param, (char*)val_as_char, (param!=10000?1:0));       // dirty hack to send INF for paramater 10000
+//  Serial.println(val);                // new value
+//  Serial.println(reg->value);         // previous value in register
+//  Serial.println(reg->address.type);  // register type (03 = holding register)
+  return val;
+}

BSB_LAN/custom_functions/Modbus_Interface/BSB_LAN_custom_setup.h

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+// Start Modbus server
+mb.server(502);                     // Start Modbus server on port 502
+
+// Callback functions
+mb.onConnect(cbConn);            // Add callback on connection event - remove this when using Modbus RTU (over serial / RS485)
+mb.onGetHreg(0, cbGet, 20720);   // add callback for get holding register request
+mb.onSetHreg(0, cbSet, 20720);   // add callback for set holding register request
+
+// Add registers that should be accessible over Modbus here. 
+// ATTENTION: These registers comsume RAM and definig too many can lead to crashes of the ESP32!
+mb.addHreg(700, 0, 100);         // add one holding register for each parameter from 700 to 799
+mb.addHreg(10000, 0, 1);         // holding register for parameter 10000
+mb.addHreg(20700, 0, 20);        // holding register for custom floats (20700-20719)