diff --git a/src/platforms/common/Makefile.inc b/src/platforms/common/Makefile.inc
index ee6a5bc..fcf4dcd 100644
--- a/src/platforms/common/Makefile.inc
+++ b/src/platforms/common/Makefile.inc
@@ -27,3 +27,4 @@ SRC +=             \
 	usb.c          \
 	usb_serial.c   \
 	usb_dfu_stub.c \
+	aux_serial.c
diff --git a/src/platforms/common/aux_serial.c b/src/platforms/common/aux_serial.c
new file mode 100644
index 0000000..72fcb87
--- /dev/null
+++ b/src/platforms/common/aux_serial.c
@@ -0,0 +1,73 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * Copyright (C) 2022 1BitSquared <info@1bitsquared.com>
+ * Written by Rachel Mant <git@dragonmux.network>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#if defined(STM32F0) || defined(STM32F1) || defined(STM32F3) || defined(STM32F4)
+#include <libopencm3/stm32/usart.h>
+#elif defined(LM4F)
+#include <libopencm3/lm4f/uart.h>
+#else
+#error "Unknown processor target"
+#endif
+#include <libopencm3/usb/usbd.h>
+#include <libopencm3/usb/cdc.h>
+
+#include "general.h"
+#include "usbuart.h"
+#include "usb.h"
+
+void usbuart_set_line_coding(struct usb_cdc_line_coding *coding)
+{
+	usart_set_baudrate(USBUSART, coding->dwDTERate);
+
+#if defined(STM32F0) || defined(STM32F1) || defined(STM32F3) || defined(STM32F4)
+	if (coding->bParityType)
+		usart_set_databits(USBUSART, (coding->bDataBits + 1 <= 8 ? 8 : 9));
+	else
+		usart_set_databits(USBUSART, (coding->bDataBits <= 8 ? 8 : 9));
+#elif defined(LM4F)
+	uart_set_databits(USBUART, coding->bDataBits);
+#endif
+
+	switch(coding->bCharFormat) {
+	case 0:
+		usart_set_stopbits(USBUSART, USART_STOPBITS_1);
+		break;
+	case 1:
+		usart_set_stopbits(USBUSART, USART_STOPBITS_1_5);
+		break;
+	case 2:
+	default:
+		usart_set_stopbits(USBUSART, USART_STOPBITS_2);
+		break;
+	}
+
+	switch(coding->bParityType) {
+	case 0:
+		usart_set_parity(USBUSART, USART_PARITY_NONE);
+		break;
+	case 1:
+		usart_set_parity(USBUSART, USART_PARITY_ODD);
+		break;
+	case 2:
+	default:
+		usart_set_parity(USBUSART, USART_PARITY_EVEN);
+		break;
+	}
+}
diff --git a/src/platforms/stm32/usbuart.c b/src/platforms/stm32/usbuart.c
index 1f37f86..0afeac5 100644
--- a/src/platforms/stm32/usbuart.c
+++ b/src/platforms/stm32/usbuart.c
@@ -192,42 +192,6 @@ void aux_serial_init(void)
 	usart_enable_rx_dma(USBUSART);
 }
 
-void usbuart_set_line_coding(struct usb_cdc_line_coding *coding)
-{
-	usart_set_baudrate(USBUSART, coding->dwDTERate);
-
-	if (coding->bParityType)
-		usart_set_databits(USBUSART, (coding->bDataBits + 1 <= 8 ? 8 : 9));
-	else
-		usart_set_databits(USBUSART, (coding->bDataBits <= 8 ? 8 : 9));
-
-	switch(coding->bCharFormat) {
-	case 0:
-		usart_set_stopbits(USBUSART, USART_STOPBITS_1);
-		break;
-	case 1:
-		usart_set_stopbits(USBUSART, USART_STOPBITS_1_5);
-		break;
-	case 2:
-	default:
-		usart_set_stopbits(USBUSART, USART_STOPBITS_2);
-		break;
-	}
-
-	switch(coding->bParityType) {
-	case 0:
-		usart_set_parity(USBUSART, USART_PARITY_NONE);
-		break;
-	case 1:
-		usart_set_parity(USBUSART, USART_PARITY_ODD);
-		break;
-	case 2:
-	default:
-		usart_set_parity(USBUSART, USART_PARITY_EVEN);
-		break;
-	}
-}
-
 /*
  * Copy data from fifo into continuous buffer. Return copied length.
  */
diff --git a/src/platforms/tm4c/usbuart.c b/src/platforms/tm4c/usbuart.c
index f598363..2e2574a 100644
--- a/src/platforms/tm4c/usbuart.c
+++ b/src/platforms/tm4c/usbuart.c
@@ -76,32 +76,6 @@ void aux_serial_init(void)
 	nvic_enable_irq(USBUART_IRQ);
 }
 
-void usbuart_set_line_coding(struct usb_cdc_line_coding *coding)
-{
-	uart_set_baudrate(USBUART, coding->dwDTERate);
-	uart_set_databits(USBUART, coding->bDataBits);
-	switch(coding->bCharFormat) {
-	case 0:
-	case 1:
-		uart_set_stopbits(USBUART, 1);
-		break;
-	case 2:
-		uart_set_stopbits(USBUART, 2);
-		break;
-	}
-	switch(coding->bParityType) {
-	case 0:
-		uart_set_parity(USBUART, UART_PARITY_NONE);
-		break;
-	case 1:
-		uart_set_parity(USBUART, UART_PARITY_ODD);
-		break;
-	case 2:
-		uart_set_parity(USBUART, UART_PARITY_EVEN);
-		break;
-	}
-}
-
 #ifndef ENABLE_RTT
 void usbuart_usb_out_cb(usbd_device *dev, uint8_t ep)
 {