diff --git a/cores/arduino/HardwareSerial.cpp b/cores/arduino/HardwareSerial.cpp
index 8554ded..2598d37 100644
--- a/cores/arduino/HardwareSerial.cpp
+++ b/cores/arduino/HardwareSerial.cpp
@@ -21,6 +21,7 @@
   Modified 14 August 2012 by Alarus
   Modified 3  December 2013 by Matthijs Kooijman
   Modified 1 may 2023 by TempersLee
+  Modified 13 October 2023 by Maxint R&D, latest update 6 May 2025
 */
 
 #include <stdio.h>
@@ -34,10 +35,22 @@ HardwareSerial::HardwareSerial(void *peripheral)
 {
   setHandler(peripheral);
 
+#if defined(PIN_SERIAL_RX) && defined(PIN_SERIAL_TX)
+  // if SERIAL_UART_INSTANCES is defined and has value 1, then PIN_SERIAL_RX and PIN_SERIAL_TX are rx/tx pins of the selected SERIAL_UART_INSTANCE
   setRx(PIN_SERIAL_RX);
-  
   setTx(PIN_SERIAL_TX);
-  
+#endif
+
+#if defined(USART2) && defined(PIN_SERIAL_RX2) && defined(PIN_SERIAL_TX2)
+  // if SERIAL_UART_INSTANCES is defined and is 2 or higher, multiple instances can be used simultaneously
+  // TODO: get pin number from pinmap PinMap_UART_TX and PinMap_UART_RX
+  if(peripheral==USART2)
+  {
+    setRx(PIN_SERIAL_RX2);
+    setTx(PIN_SERIAL_TX2);
+  }
+#endif
+
   init(_serial.pin_rx, _serial.pin_tx);
 }
 
@@ -57,6 +70,48 @@ void HardwareSerial::init(PinName _rx, PinName _tx, PinName _rts, PinName _cts)
 }
 
 
+// Interrupt handler for filling rx buffer /////////////////////////////////////
+#if(OPT_USART_INT==1)
+  #ifdef __cplusplus
+  extern "C" {
+  #endif
+
+#if defined(USART1)
+  #if defined(HAVE_HWSERIAL1)
+    void USART1_IRQHandler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
+    void USART1_IRQHandler(void) {
+      USART_ClearITPendingBit(USART1, USART_IT_RXNE);
+      // Use the proper serial object to fill the RX buffer. Perhaps we should use uart_handlers[] as defined in uart.c
+      // Serial is most often Serial1, initialized below as HardwareSerial Serial1(USART1); DEBUG_UART may give issues.
+      // TODO? get_serial_obj(uart_handlers[UART1_INDEX]);
+      HardwareSerial *obj=&Serial1; 
+      obj->_rx_buffer[obj->_rx_buffer_head] = USART_ReceiveData(USART1);    // maybe we should use uart_getc()?
+      obj->_rx_buffer_head++;
+      obj->_rx_buffer_head %= SERIAL_RX_BUFFER_SIZE;
+    }
+  #endif 
+#endif
+
+#if defined(USART2)
+  #if defined(HAVE_HWSERIAL2)
+    void USART2_IRQHandler(void) __attribute__((interrupt("WCH-Interrupt-fast")));
+    void USART2_IRQHandler(void) {
+      USART_ClearITPendingBit(USART2, USART_IT_RXNE);
+      // Use the proper serial object to fill the RX buffer. Perhaps we should use uart_handlers[] as defined in uart.c
+      // Second Serial is most often Serial2, initialized below as HardwareSerial Serial2(USART2); DEBUG_UART may give issues.
+      // TODO? get_serial_obj(uart_handlers[UART2_INDEX]);
+      HardwareSerial *obj=&Serial2; 
+      obj->_rx_buffer[obj->_rx_buffer_head] = USART_ReceiveData(USART2);    // maybe we should use uart_getc()?
+      obj->_rx_buffer_head++;
+      obj->_rx_buffer_head %= SERIAL_RX_BUFFER_SIZE;
+    }
+  #endif
+#endif
+
+  #ifdef __cplusplus
+  }
+  #endif
+#endif //if(OPT_USART_INT==1)
 
 // Public Methods //////////////////////////////////////////////////////////////
 void HardwareSerial::begin(unsigned long baud, byte config)
@@ -138,46 +193,99 @@ void HardwareSerial::begin(unsigned long baud, byte config)
       break;
   }
   uart_init(&_serial, (uint32_t)baud, databits, parity, stopbits);
+
+#if(OPT_USART_INT==1)
+  // MMOLE 240619: Enable interrupt handler for filling rx buffer
+  #if defined(USART1)
+    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
+    NVIC_SetPriority(USART1_IRQn, UART_IRQ_PRIO);
+    NVIC_EnableIRQ(USART1_IRQn);
+  #endif
+  // MMOLE TODO: I only have CH32V003/CH32X033; only tested USART1 and USART2, how about others?
+  #if defined(USART2)
+    USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);
+    NVIC_SetPriority(USART2_IRQn, UART_IRQ_PRIO);
+    NVIC_EnableIRQ(USART2_IRQn);
+  #endif
+#endif
 }
 
 void HardwareSerial::end()
 {
+  // MMOLE: reintroduced RX buffer to properly implement read/available/peek methods
+  // clear any received data
+  _rx_buffer_head = _rx_buffer_tail;
+
   uart_deinit(&_serial);
+
+#if(OPT_USART_INT==1)
+  // MMOLE TODO: disable interrupt handlers
+#endif
 }
 
 int HardwareSerial::available(void)
 {
-  return -1;
+  // MMOLE: reintroduced RX buffer to properly implement read/available/peek methods
+  //return -1;
+  return ((unsigned int)(SERIAL_RX_BUFFER_SIZE + _rx_buffer_head - _rx_buffer_tail)) % SERIAL_RX_BUFFER_SIZE;
 }
 
 int HardwareSerial::peek(void)
 {
-   return -1;
+  // MMOLE: reintroduced RX buffer to properly implement read/available/peek methods
+  // MMOLE 240316: Serial.parseInt() uses peek() with timeout to see if more data is available
+   //return -1;
+  if (_rx_buffer_head == _rx_buffer_tail) {
+    return -1;
+  } else {
+    return _rx_buffer[_rx_buffer_tail];
+  }
 }
 
 int HardwareSerial::read(void)
 {
-
   unsigned char c;
+  // MMOLE: reintroduced RX buffer to properly implement read/available/peek methods
+/*
   if(uart_getc(&_serial, &c) == 0){
     return c;
   }else{
     return -1;
   }
+*/
+
+  // if the head isn't ahead of the tail, we don't have any characters
+  if (_rx_buffer_head == _rx_buffer_tail) {
+    return -1;
+  } else {
+    unsigned char c = _rx_buffer[_rx_buffer_tail];
+    _rx_buffer_tail = (rx_buffer_index_t)(_rx_buffer_tail + 1) % SERIAL_RX_BUFFER_SIZE;
+    return c;
+  }
 }
 
 
 size_t HardwareSerial::write(const uint8_t *buffer, size_t size)
 {
-
+#if OPT_PR180 // PR180: HardwareSerial: use correct UART HW for TX
+    for (size_t i = 0; i < size; i++) {
+      write(buffer[i]);
+    }
+    return size;
+#else
     return  uart_debug_write((uint8_t *)buffer, size);
+#endif
 }
 
 
 size_t HardwareSerial::write(uint8_t c)
 {
+#if OPT_PR180 // PR180: HardwareSerial: use correct UART HW for TX
+  return uart_putc(&_serial, c);
+#else
   uint8_t buff = c;
   return write(&buff, 1);
+#endif
 }
 
 void HardwareSerial::setRx(uint32_t _rx)
diff --git a/cores/arduino/HardwareSerial.h b/cores/arduino/HardwareSerial.h
index 0f28f10..a52da82 100644
--- a/cores/arduino/HardwareSerial.h
+++ b/cores/arduino/HardwareSerial.h
@@ -19,12 +19,17 @@
   Modified 28 September 2010 by Mark Sproul
   Modified 14 August 2012 by Alarus
   Modified 3 December 2013 by Matthijs Kooijman
-  Modified 1 may 2023 by TempersLee
+  Modified 1 May 2023 by TempersLee
+  Modified 13 October 2023 by Maxint R&D, latest update 6 May 2025
 */
 
 #ifndef HardwareSerial_h
 #define HardwareSerial_h
 
+// MMOLE 240619: set OPT_USART_INT to 1 if you want to use interrupts for receiving serial data.
+#define OPT_USART_INT 1
+#define OPT_PR180 1  // PR180: HardwareSerial: use correct UART HW for TX
+
 #if 1
 
 #include <inttypes.h>
@@ -101,6 +106,9 @@ typedef enum {
 
 class HardwareSerial : public Stream {
 
+#if(OPT_USART_INT==1)
+public:
+#endif
   serial_t _serial;  
 public:
     HardwareSerial(void *peripheral); 
@@ -109,6 +117,17 @@ class HardwareSerial : public Stream {
     {
       begin(baud, SERIAL_8N1);     //SERIAL_9E1_5  SERIAL_8N1
     }
+    // MMOLE: reintroduced RX buffer to properly implement read/available/peek methods
+    volatile rx_buffer_index_t _rx_buffer_head;
+    volatile rx_buffer_index_t _rx_buffer_tail;
+    //volatile tx_buffer_index_t _tx_buffer_head;
+    //volatile tx_buffer_index_t _tx_buffer_tail;
+
+    // Don't put any members after these buffers, since only the first
+    // 32 bytes of this struct can be accessed quickly using the ldd
+    // instruction.
+    unsigned char _rx_buffer[SERIAL_RX_BUFFER_SIZE];
+    //unsigned char _tx_buffer[SERIAL_TX_BUFFER_SIZE];
     void begin(unsigned long, uint8_t);
     void end();
 
@@ -173,22 +192,22 @@ class HardwareSerial : public Stream {
 #if defined(UART4) || defined(USART4)
   extern HardwareSerial Serial4;
 #endif
-#if defined(UART5) 
+#if defined(UART5) || defined(USART5)
   extern HardwareSerial Serial5;
 #endif
-#if defined(UART6) 
+#if defined(UART6) || defined(USART6)
   extern HardwareSerial Serial6;
 #endif
-#if defined(UART7) 
+#if defined(UART7) || defined(USART7)
   extern HardwareSerial Serial7;
 #endif
-#if defined(UART8) 
+#if defined(UART8) || defined(USART8)
   extern HardwareSerial Serial8;
 #endif
 
 
 
-#else
+#else  // #if 1
 
 
 
@@ -196,7 +215,7 @@ class HardwareSerial : public Stream {
 
 
 
-#endif
+#endif  // #if 1
 
 
 
diff --git a/cores/arduino/ch32/uart.c b/cores/arduino/ch32/uart.c
index 3707072..5e0681b 100644
--- a/cores/arduino/ch32/uart.c
+++ b/cores/arduino/ch32/uart.c
@@ -528,6 +528,31 @@ int uart_getc(serial_t *obj, unsigned char *c)
   return 0;
 }
 
+// PR180: HardwareSerial: use correct UART HW for TX
+/**
+  * @brief  Write byte to uart
+  * @param  obj : pointer to serial_t structure
+  * @retval error status
+  */
+int uart_putc(serial_t *obj, unsigned char c)
+{
+  uint32_t tickstart = GetTick();
+
+  if (obj == NULL) {
+    return -1;
+  }
+
+  while (serial_tx_active(obj))
+  {
+    if ((GetTick() - tickstart) >= TX_TIMEOUT)
+    {
+      return 0; // 0 means no error? Should be timeout error?
+    }
+  }
+
+  USART_SendData(uart_handlers[obj->index]->Instance, c);
+  return 0; // 0 means no error
+}
 
 
 
diff --git a/cores/arduino/ch32/uart.h b/cores/arduino/ch32/uart.h
index 1a1e905..3b9883d 100644
--- a/cores/arduino/ch32/uart.h
+++ b/cores/arduino/ch32/uart.h
@@ -90,6 +90,7 @@ typedef struct __UART_HandleTypeDef
   void uart_deinit(serial_t *obj);
 
   int uart_getc(serial_t *obj, unsigned char *c);
+  int uart_putc(serial_t *obj, unsigned char c);  // PR180: HardwareSerial: use correct UART HW for TX
 
   uint8_t serial_tx_active(serial_t *obj);
   uint8_t serial_rx_active(serial_t *obj);