diff --git a/src/ModbusRTUClient.cpp b/src/ModbusRTUClient.cpp
index 8249590..b9c25bb 100644
--- a/src/ModbusRTUClient.cpp
+++ b/src/ModbusRTUClient.cpp
@@ -34,9 +34,9 @@ ModbusRTUClientClass::~ModbusRTUClientClass()
 {
 }
 
-int ModbusRTUClientClass::begin(unsigned long baudrate, uint16_t config)
+int ModbusRTUClientClass::begin(unsigned long baudrate, uint16_t config, RS485Class& rs485)
 {
-  modbus_t* mb = modbus_new_rtu(baudrate, config);
+  modbus_t* mb = modbus_new_rtu(baudrate, config, &rs485);
 
   if (!ModbusClient::begin(mb, 0x00)) {
     return 0;
@@ -47,4 +47,9 @@ int ModbusRTUClientClass::begin(unsigned long baudrate, uint16_t config)
   return 1;
 }
 
+int ModbusRTUClientClass::begin(unsigned long baudrate, RS485Class& rs485)
+{
+  return begin(baudrate, SERIAL_8N1, rs485);
+}
+
 ModbusRTUClientClass ModbusRTUClient;
diff --git a/src/ModbusRTUClient.h b/src/ModbusRTUClient.h
index 2dc96c9..9264aeb 100644
--- a/src/ModbusRTUClient.h
+++ b/src/ModbusRTUClient.h
@@ -22,6 +22,8 @@
 
 #include "ModbusClient.h"
 
+#include <ArduinoRS485.h>
+
 class ModbusRTUClientClass : public ModbusClient {
 public:
   ModbusRTUClientClass();
@@ -35,7 +37,8 @@ class ModbusRTUClientClass : public ModbusClient {
    *
    * Return 1 on success, 0 on failure
    */
-  int begin(unsigned long baudrate, uint16_t config = SERIAL_8N1);
+  int begin(unsigned long baudrate, uint16_t config = SERIAL_8N1, RS485Class& rs485 = RS485);
+  int begin(unsigned long baudrate, RS485Class& rs485);
 };
 
 extern ModbusRTUClientClass ModbusRTUClient;
diff --git a/src/ModbusRTUServer.cpp b/src/ModbusRTUServer.cpp
index 7c4dfb9..03bd93d 100644
--- a/src/ModbusRTUServer.cpp
+++ b/src/ModbusRTUServer.cpp
@@ -34,9 +34,9 @@ ModbusRTUServerClass::~ModbusRTUServerClass()
 {
 }
 
-int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config)
+int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config, RS485Class& rs485)
 {
-  modbus_t* mb = modbus_new_rtu(baudrate, config);
+  modbus_t* mb = modbus_new_rtu(baudrate, config, &rs485);
 
   if (!ModbusServer::begin(mb, id)) {
     return 0;
@@ -47,6 +47,11 @@ int ModbusRTUServerClass::begin(int id, unsigned long baudrate, uint16_t config)
   return 1;
 }
 
+int ModbusRTUServerClass::begin(int id, unsigned long baudrate, RS485Class& rs485)
+{
+  return begin(id, baudrate, SERIAL_8N1, RS485);
+}
+
 void ModbusRTUServerClass::poll()
 {
   uint8_t request[MODBUS_RTU_MAX_ADU_LENGTH];
diff --git a/src/ModbusRTUServer.h b/src/ModbusRTUServer.h
index 82cd885..04176b6 100644
--- a/src/ModbusRTUServer.h
+++ b/src/ModbusRTUServer.h
@@ -22,6 +22,8 @@
 
 #include "ModbusServer.h"
 
+#include <ArduinoRS485.h>
+
 class ModbusRTUServerClass : public ModbusServer {
 public:
   ModbusRTUServerClass();
@@ -36,7 +38,8 @@ class ModbusRTUServerClass : public ModbusServer {
    *
    * Return 1 on success, 0 on failure
    */
-  int begin(int id, unsigned long baudrate, uint16_t config = SERIAL_8N1);
+  int begin(int id, unsigned long baudrate, uint16_t config = SERIAL_8N1, RS485Class& rs485 = RS485);
+  int begin(int id, unsigned long baudrate, RS485Class& rs485);
 
   /**
    * Poll interface for requests
diff --git a/src/libmodbus/modbus-rtu-private.h b/src/libmodbus/modbus-rtu-private.h
index 736cbce..5cd6a8b 100644
--- a/src/libmodbus/modbus-rtu-private.h
+++ b/src/libmodbus/modbus-rtu-private.h
@@ -17,7 +17,7 @@
 #if defined(_WIN32)
 #include <windows.h>
 #elif defined(ARDUINO)
-// nothing extra needed
+#include <ArduinoRS485.h>
 #else
 #include <termios.h>
 #endif
@@ -49,6 +49,7 @@ typedef struct _modbus_rtu {
 #if defined(ARDUINO)
     unsigned long baud;
     uint16_t config;
+    RS485Class* rs485;
 #else
     /* Device: "/dev/ttyS0", "/dev/ttyUSB0" or "/dev/tty.USA19*" on Mac OS X. */
     char *device;
diff --git a/src/libmodbus/modbus-rtu.cpp b/src/libmodbus/modbus-rtu.cpp
index d24b520..29f8e50 100644
--- a/src/libmodbus/modbus-rtu.cpp
+++ b/src/libmodbus/modbus-rtu.cpp
@@ -16,7 +16,6 @@
 #include <assert.h>
 
 #ifdef ARDUINO
-#include <ArduinoRS485.h>
 
 #ifndef DEBUG
 #define printf(...) {}
@@ -323,15 +322,17 @@ static ssize_t _modbus_rtu_send(modbus_t *ctx, const uint8_t *req, int req_lengt
     DWORD n_bytes = 0;
     return (WriteFile(ctx_rtu->w_ser.fd, req, req_length, &n_bytes, NULL)) ? (ssize_t)n_bytes : -1;
 #elif defined(ARDUINO)
+    modbus_rtu_t *ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
     (void)ctx;
 
     ssize_t size;
 
-    RS485.noReceive();
-    RS485.beginTransmission();
-    size = RS485.write(req, req_length);
-    RS485.endTransmission();
-    RS485.receive();
+    rs485->noReceive();
+    rs485->beginTransmission();
+    size = rs485->write(req, req_length);
+    rs485->endTransmission();
+    rs485->receive();
 
     return size;
 #else
@@ -394,9 +395,11 @@ static ssize_t _modbus_rtu_recv(modbus_t *ctx, uint8_t *rsp, int rsp_length)
 #if defined(_WIN32)
     return win32_ser_read(&((modbus_rtu_t *)ctx->backend_data)->w_ser, rsp, rsp_length);
 #elif defined(ARDUINO)
+    modbus_rtu_t *ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
     (void)ctx;
 
-    return RS485.readBytes(rsp, rsp_length);
+    return rs485->readBytes(rsp, rsp_length);
 #else
     return read(ctx->s, rsp, rsp_length);
 #endif
@@ -479,6 +482,7 @@ static int _modbus_rtu_connect(modbus_t *ctx)
 #endif
 #ifdef ARDUINO
     modbus_rtu_t *ctx_rtu = (modbus_rtu_t*)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
 #else
     modbus_rtu_t *ctx_rtu = ctx->backend_data;
 
@@ -654,8 +658,8 @@ static int _modbus_rtu_connect(modbus_t *ctx)
         return -1;
     }
 #elif defined(ARDUINO)
-    RS485.begin(ctx_rtu->baud, ctx_rtu->config);
-    RS485.receive();
+    rs485->begin(ctx_rtu->baud, ctx_rtu->config);
+    rs485->receive();
 #else
     /* The O_NOCTTY flag tells UNIX that this program doesn't want
        to be the "controlling terminal" for that port. If you
@@ -1192,6 +1196,7 @@ static void _modbus_rtu_close(modbus_t *ctx)
     /* Restore line settings and close file descriptor in RTU mode */
 #ifdef ARDUINO
     modbus_rtu_t *ctx_rtu = (modbus_rtu_t*)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
 #else
     modbus_rtu_t *ctx_rtu = ctx->backend_data;
 #endif
@@ -1210,8 +1215,8 @@ static void _modbus_rtu_close(modbus_t *ctx)
 #elif defined(ARDUINO)
     (void)ctx_rtu;
 
-    RS485.noReceive();
-    RS485.end();
+    rs485->noReceive();
+    rs485->end();
 #else
     if (ctx->s != -1) {
         tcsetattr(ctx->s, TCSANOW, &ctx_rtu->old_tios);
@@ -1228,10 +1233,12 @@ static int _modbus_rtu_flush(modbus_t *ctx)
     ctx_rtu->w_ser.n_bytes = 0;
     return (PurgeComm(ctx_rtu->w_ser.fd, PURGE_RXCLEAR) == FALSE);
 #elif defined(ARDUINO)
+    modbus_rtu_t *ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
     (void)ctx;
 
-    while (RS485.available()) {
-        RS485.read();
+    while (rs485->available()) {
+        rs485->read();
     }
 
     return 0;
@@ -1256,6 +1263,8 @@ static int _modbus_rtu_select(modbus_t *ctx, fd_set *rset,
         return -1;
     }
 #elif defined(ARDUINO)
+    modbus_rtu_t *ctx_rtu = (modbus_rtu_t *)ctx->backend_data;
+    RS485Class *rs485 = ctx_rtu->rs485;
     (void)ctx;
     (void)rset;
 
@@ -1263,7 +1272,7 @@ static int _modbus_rtu_select(modbus_t *ctx, fd_set *rset,
     unsigned long start = millis();
 
     do {
-        s_rc = RS485.available();
+        s_rc = rs485->available();
 
         if (s_rc >= length_to_read) {
             break;
@@ -1330,7 +1339,7 @@ const modbus_backend_t _modbus_rtu_backend = {
 };
 
 #ifdef ARDUINO
-modbus_t* modbus_new_rtu(unsigned long baud, uint16_t config)
+modbus_t* modbus_new_rtu(unsigned long baud, uint16_t config, RS485Class* rs485)
 #else
 modbus_t* modbus_new_rtu(const char *device,
                          int baud, char parity, int data_bit,
@@ -1364,6 +1373,7 @@ modbus_t* modbus_new_rtu(const char *device,
 #ifdef ARDUINO
     ctx_rtu->baud = baud;
     ctx_rtu->config = config;
+    ctx_rtu->rs485 = rs485;
 #else
     ctx_rtu->device = NULL;
 
diff --git a/src/libmodbus/modbus-rtu.h b/src/libmodbus/modbus-rtu.h
index 1237403..4c55789 100644
--- a/src/libmodbus/modbus-rtu.h
+++ b/src/libmodbus/modbus-rtu.h
@@ -8,8 +8,13 @@
 #ifndef MODBUS_RTU_H
 #define MODBUS_RTU_H
 
+#ifdef ARDUINO
+class RS485Class;
+#endif
+
 #include "modbus.h"
 
+
 MODBUS_BEGIN_DECLS
 
 /* Modbus_Application_Protocol_V1_1b.pdf Chapter 4 Section 1 Page 5
@@ -18,7 +23,7 @@ MODBUS_BEGIN_DECLS
 #define MODBUS_RTU_MAX_ADU_LENGTH  256
 
 #ifdef ARDUINO
-MODBUS_API modbus_t* modbus_new_rtu(unsigned long baud, uint16_t config);
+MODBUS_API modbus_t* modbus_new_rtu(unsigned long baud, uint16_t config, RS485Class* rs485);
 #else
 MODBUS_API modbus_t* modbus_new_rtu(const char *device, int baud, char parity,
                                     int data_bit, int stop_bit);