diff --git a/src/main/drivers/serial.c b/src/main/drivers/serial.c
index c6cab03d7..4cb8cb390 100644
--- a/src/main/drivers/serial.c
+++ b/src/main/drivers/serial.c
@@ -56,12 +56,12 @@ void serialWriteBuf(serialPort_t *instance, uint8_t *data, int count)
     }
 }
 
-uint32_t serialRxBytesWaiting(serialPort_t *instance)
+uint32_t serialRxBytesWaiting(const serialPort_t *instance)
 {
     return instance->vTable->serialTotalRxWaiting(instance);
 }
 
-uint32_t serialTxBytesFree(serialPort_t *instance)
+uint32_t serialTxBytesFree(const serialPort_t *instance)
 {
     return instance->vTable->serialTotalTxFree(instance);
 }
@@ -76,7 +76,7 @@ void serialSetBaudRate(serialPort_t *instance, uint32_t baudRate)
     instance->vTable->serialSetBaudRate(instance, baudRate);
 }
 
-bool isSerialTransmitBufferEmpty(serialPort_t *instance)
+bool isSerialTransmitBufferEmpty(const serialPort_t *instance)
 {
     return instance->vTable->isSerialTransmitBufferEmpty(instance);
 }
diff --git a/src/main/drivers/serial.h b/src/main/drivers/serial.h
index fa855e835..279e3f5de 100644
--- a/src/main/drivers/serial.h
+++ b/src/main/drivers/serial.h
@@ -62,15 +62,15 @@ typedef struct serialPort_s {
 struct serialPortVTable {
     void (*serialWrite)(serialPort_t *instance, uint8_t ch);
 
-    uint32_t (*serialTotalRxWaiting)(serialPort_t *instance);
-    uint32_t (*serialTotalTxFree)(serialPort_t *instance);
+    uint32_t (*serialTotalRxWaiting)(const serialPort_t *instance);
+    uint32_t (*serialTotalTxFree)(const serialPort_t *instance);
 
     uint8_t (*serialRead)(serialPort_t *instance);
 
     // Specified baud rate may not be allowed by an implementation, use serialGetBaudRate to determine actual baud rate in use.
     void (*serialSetBaudRate)(serialPort_t *instance, uint32_t baudRate);
 
-    bool (*isSerialTransmitBufferEmpty)(serialPort_t *instance);
+    bool (*isSerialTransmitBufferEmpty)(const serialPort_t *instance);
 
     void (*setMode)(serialPort_t *instance, portMode_t mode);
 
@@ -81,13 +81,13 @@ struct serialPortVTable {
 };
 
 void serialWrite(serialPort_t *instance, uint8_t ch);
-uint32_t serialRxBytesWaiting(serialPort_t *instance);
-uint32_t serialTxBytesFree(serialPort_t *instance);
+uint32_t serialRxBytesWaiting(const serialPort_t *instance);
+uint32_t serialTxBytesFree(const serialPort_t *instance);
 void serialWriteBuf(serialPort_t *instance, uint8_t *data, int count);
 uint8_t serialRead(serialPort_t *instance);
 void serialSetBaudRate(serialPort_t *instance, uint32_t baudRate);
 void serialSetMode(serialPort_t *instance, portMode_t mode);
-bool isSerialTransmitBufferEmpty(serialPort_t *instance);
+bool isSerialTransmitBufferEmpty(const serialPort_t *instance);
 void serialPrint(serialPort_t *instance, const char *str);
 uint32_t serialGetBaudRate(serialPort_t *instance);
 
diff --git a/src/main/drivers/serial_softserial.c b/src/main/drivers/serial_softserial.c
index 03ecf5745..fa04943f4 100644
--- a/src/main/drivers/serial_softserial.c
+++ b/src/main/drivers/serial_softserial.c
@@ -401,7 +401,7 @@ void onSerialRxPinChange(timerCCHandlerRec_t *cbRec, captureCompare_t capture)
     }
 }
 
-uint32_t softSerialRxBytesWaiting(serialPort_t *instance)
+uint32_t softSerialRxBytesWaiting(const serialPort_t *instance)
 {
     if ((instance->mode & MODE_RX) == 0) {
         return 0;
@@ -412,7 +412,7 @@ uint32_t softSerialRxBytesWaiting(serialPort_t *instance)
     return (s->port.rxBufferHead - s->port.rxBufferTail) & (s->port.rxBufferSize - 1);
 }
 
-uint32_t softSerialTxBytesFree(serialPort_t *instance)
+uint32_t softSerialTxBytesFree(const serialPort_t *instance)
 {
     if ((instance->mode & MODE_TX) == 0) {
         return 0;
@@ -463,7 +463,7 @@ void softSerialSetMode(serialPort_t *instance, portMode_t mode)
     instance->mode = mode;
 }
 
-bool isSoftSerialTransmitBufferEmpty(serialPort_t *instance)
+bool isSoftSerialTransmitBufferEmpty(const serialPort_t *instance)
 {
     return instance->txBufferHead == instance->txBufferTail;
 }
diff --git a/src/main/drivers/serial_softserial.h b/src/main/drivers/serial_softserial.h
index eb569c9fa..f831682b1 100644
--- a/src/main/drivers/serial_softserial.h
+++ b/src/main/drivers/serial_softserial.h
@@ -28,9 +28,9 @@ serialPort_t *openSoftSerial(softSerialPortIndex_e portIndex, serialReceiveCallb
 
 // serialPort API
 void softSerialWriteByte(serialPort_t *instance, uint8_t ch);
-uint32_t softSerialRxBytesWaiting(serialPort_t *instance);
-uint32_t softSerialTxBytesFree(serialPort_t *instance);
+uint32_t softSerialRxBytesWaiting(const serialPort_t *instance);
+uint32_t softSerialTxBytesFree(const serialPort_t *instance);
 uint8_t softSerialReadByte(serialPort_t *instance);
 void softSerialSetBaudRate(serialPort_t *s, uint32_t baudRate);
-bool isSoftSerialTransmitBufferEmpty(serialPort_t *s);
+bool isSoftSerialTransmitBufferEmpty(const serialPort_t *s);
 
diff --git a/src/main/drivers/serial_uart.c b/src/main/drivers/serial_uart.c
index 88f422f2e..2b6eb8122 100644
--- a/src/main/drivers/serial_uart.c
+++ b/src/main/drivers/serial_uart.c
@@ -291,9 +291,9 @@ void uartStartTxDMA(uartPort_t *s)
 #endif
 }
 
-uint32_t uartTotalRxBytesWaiting(serialPort_t *instance)
+uint32_t uartTotalRxBytesWaiting(const serialPort_t *instance)
 {
-    uartPort_t *s = (uartPort_t*)instance;
+    const uartPort_t *s = (const uartPort_t*)instance;
 #ifdef STM32F4
     if (s->rxDMAStream) {
         uint32_t rxDMAHead = s->rxDMAStream->NDTR;
@@ -315,9 +315,9 @@ uint32_t uartTotalRxBytesWaiting(serialPort_t *instance)
     }
 }
 
-uint32_t uartTotalTxBytesFree(serialPort_t *instance)
+uint32_t uartTotalTxBytesFree(const serialPort_t *instance)
 {
-    uartPort_t *s = (uartPort_t*)instance;
+    const uartPort_t *s = (const uartPort_t*)instance;
 
     uint32_t bytesUsed;
 
@@ -358,9 +358,9 @@ uint32_t uartTotalTxBytesFree(serialPort_t *instance)
     return (s->port.txBufferSize - 1) - bytesUsed;
 }
 
-bool isUartTransmitBufferEmpty(serialPort_t *instance)
+bool isUartTransmitBufferEmpty(const serialPort_t *instance)
 {
-    uartPort_t *s = (uartPort_t *)instance;
+    const uartPort_t *s = (const uartPort_t *)instance;
 #ifdef STM32F4
     if (s->txDMAStream)
 #else
diff --git a/src/main/drivers/serial_uart.h b/src/main/drivers/serial_uart.h
index a8c0d64b2..f54310d75 100644
--- a/src/main/drivers/serial_uart.h
+++ b/src/main/drivers/serial_uart.h
@@ -65,8 +65,8 @@ serialPort_t *uartOpen(USART_TypeDef *USARTx, serialReceiveCallbackPtr callback,
 
 // serialPort API
 void uartWrite(serialPort_t *instance, uint8_t ch);
-uint32_t uartTotalRxBytesWaiting(serialPort_t *instance);
-uint32_t uartTotalTxBytesFree(serialPort_t *instance);
+uint32_t uartTotalRxBytesWaiting(const serialPort_t *instance);
+uint32_t uartTotalTxBytesFree(const serialPort_t *instance);
 uint8_t uartRead(serialPort_t *instance);
 void uartSetBaudRate(serialPort_t *s, uint32_t baudRate);
-bool isUartTransmitBufferEmpty(serialPort_t *s);
+bool isUartTransmitBufferEmpty(const serialPort_t *s);