diff --git a/teensy3/serial1.c b/teensy3/serial1.c
index 9262c342e..3747d4377 100644
--- a/teensy3/serial1.c
+++ b/teensy3/serial1.c
@@ -114,6 +114,9 @@ static uint8_t tx_pin_num = 1;
 static uint8_t half_duplex_mode = 0;
 #endif
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -202,6 +205,14 @@ void serial_format(uint32_t format)
 	c = UART0_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART0_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #ifdef SERIAL_9BIT_SUPPORT
 	c = UART0_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -628,7 +639,7 @@ void uart0_status_isr(void)
 				if (use9Bits && (UART0_C3 & 0x80)) {
 					n = UART0_D | 0x100;
 				} else {
-					n = UART0_D;
+					n = UART0_D & data_mask;
 				}
 				newhead = head + 1;
 				if (newhead >= rx_buffer_total_size_) newhead = 0;
@@ -674,7 +685,7 @@ void uart0_status_isr(void)
 		if (use9Bits && (UART0_C3 & 0x80)) {
 			n = UART0_D | 0x100;
 		} else {
-			n = UART0_D;
+			n = UART0_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial1_doughboy.txt b/teensy3/serial1_doughboy.txt
index 3eeda9bc7..d95bece66 100644
--- a/teensy3/serial1_doughboy.txt
+++ b/teensy3/serial1_doughboy.txt
@@ -89,6 +89,9 @@ static volatile uint8_t rx_buffer_head = 0;
 static volatile uint8_t rx_buffer_tail = 0;
 #endif
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -140,6 +143,14 @@ void serial_format(uint32_t format)
 	c = UART0_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART0_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #ifdef SERIAL_9BIT_SUPPORT
 	c = UART0_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -404,7 +415,7 @@ void uart0_status_isr(void)
 				if (use9Bits && (UART0_C3 & 0x80)) {
 					n = UART0_D | 0x100;
 				} else {
-					n = UART0_D;
+					n = UART0_D & data_mask;
 				}
 				head = newhead;
 				rx_buffer[head] = n;
@@ -442,7 +453,11 @@ void uart0_status_isr(void)
 				}
 			}
 			n = UART0_D;
-			if (use9Bits && (UART0_C3 & 0x80)) n |= 0x100;
+			if (use9Bits && (UART0_C3 & 0x80)) {
+				n |= 0x100;
+			} else {
+				n &= data_mask;
+			}
 			rx_buffer[head] = n;
 			rx_buffer_head = head;
 			break;
diff --git a/teensy3/serial2.c b/teensy3/serial2.c
index 15109a729..4ffc673ba 100644
--- a/teensy3/serial2.c
+++ b/teensy3/serial2.c
@@ -115,6 +115,9 @@ static uint8_t tx_pin_num = 10;
 static uint8_t half_duplex_mode = 0;
 #endif
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -201,6 +204,14 @@ void serial2_format(uint32_t format)
 	c = UART1_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART1_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #if defined(SERIAL_9BIT_SUPPORT) && !defined(KINETISL)
 	c = UART1_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -613,7 +624,7 @@ void uart1_status_isr(void)
 				if (use9Bits && (UART1_C3 & 0x80)) {
 					n = UART1_D | 0x100;
 				} else {
-					n = UART1_D;
+					n = UART1_D & data_mask;
 				}
 				newhead = head + 1;
 				if (newhead >= rx_buffer_total_size_) newhead = 0;
@@ -659,7 +670,7 @@ void uart1_status_isr(void)
 		if (use9Bits && (UART1_C3 & 0x80)) {
 			n = UART1_D | 0x100;
 		} else {
-			n = UART1_D;
+			n = UART1_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial3.c b/teensy3/serial3.c
index 94442a6b5..8f5cbfd01 100644
--- a/teensy3/serial3.c
+++ b/teensy3/serial3.c
@@ -117,6 +117,9 @@ static uint8_t tx_pin_num = 8;
 static uint8_t half_duplex_mode = 0;
 #endif
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -184,6 +187,14 @@ void serial3_format(uint32_t format)
 	c = UART2_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART2_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #if defined(SERIAL_9BIT_SUPPORT) && !defined(KINETISL)
 	c = UART2_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -492,7 +503,7 @@ void uart2_status_isr(void)
 		if (use9Bits && (UART2_C3 & 0x80)) {
 			n = UART2_D | 0x100;
 		} else {
-			n = UART2_D;
+			n = UART2_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial4.c b/teensy3/serial4.c
index 0869fcf22..bd898b586 100644
--- a/teensy3/serial4.c
+++ b/teensy3/serial4.c
@@ -102,6 +102,9 @@ static volatile uint8_t rx_buffer_tail = 0;
 static uint8_t rx_pin_num = 31;
 static uint8_t tx_pin_num = 32;
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -157,6 +160,14 @@ void serial4_format(uint32_t format)
 	c = UART3_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART3_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #ifdef SERIAL_9BIT_SUPPORT
 	c = UART3_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -412,7 +423,7 @@ void uart3_status_isr(void)
 		if (use9Bits && (UART3_C3 & 0x80)) {
 			n = UART3_D | 0x100;
 		} else {
-			n = UART3_D;
+			n = UART3_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial5.c b/teensy3/serial5.c
index 9037ec600..3a90abc30 100644
--- a/teensy3/serial5.c
+++ b/teensy3/serial5.c
@@ -102,6 +102,9 @@ static volatile uint8_t rx_buffer_tail = 0;
 
 static uint8_t tx_pin_num = 33;
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -151,6 +154,14 @@ void serial5_format(uint32_t format)
 	c = UART4_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART4_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #ifdef SERIAL_9BIT_SUPPORT
 	c = UART4_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -383,7 +394,7 @@ void uart4_status_isr(void)
 		if (use9Bits && (UART4_C3 & 0x80)) {
 			n = UART4_D | 0x100;
 		} else {
-			n = UART4_D;
+			n = UART4_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial6.c b/teensy3/serial6.c
index 22eebab36..d9ceaeac8 100644
--- a/teensy3/serial6.c
+++ b/teensy3/serial6.c
@@ -102,6 +102,9 @@ static volatile uint8_t rx_buffer_tail = 0;
 
 static uint8_t tx_pin_num = 48;
 
+// 7-bit mode support
+static uint8_t data_mask = 0xff;  // Use all bits by default
+
 // UART0 and UART1 are clocked by F_CPU, UART2 is clocked by F_BUS
 // UART0 has 8 byte fifo, UART1 and UART2 have 1 byte buffer
 
@@ -151,6 +154,14 @@ void serial6_format(uint32_t format)
 	c = UART5_C3 & ~0x10;
 	if (format & 0x20) c |= 0x10;		// tx invert
 	UART5_C3 = c;
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0xff;	// Use all bits
+	}
+
 #ifdef SERIAL_9BIT_SUPPORT
 	c = UART5_C4 & 0x1F;
 	if (format & 0x08) c |= 0x20;		// 9 bit mode with parity (requires 10 bits)
@@ -382,7 +393,7 @@ void uart5_status_isr(void)
 		if (use9Bits && (UART5_C3 & 0x80)) {
 			n = UART5_D | 0x100;
 		} else {
-			n = UART5_D;
+			n = UART5_D & data_mask;
 		}
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
diff --git a/teensy3/serial6_lpuart.c b/teensy3/serial6_lpuart.c
index efbf030f0..06c23048b 100644
--- a/teensy3/serial6_lpuart.c
+++ b/teensy3/serial6_lpuart.c
@@ -110,6 +110,9 @@ static volatile uint8_t rx_buffer_tail = 0;
 
 static uint8_t tx_pin_num = 48;
 
+// 7-bit mode support
+static uint32_t data_mask = 0x3ff;  // Use only the 10 data bits by default
+
 
 void serial6_begin(uint32_t desiredBaudRate)
 {
@@ -224,7 +227,14 @@ void serial6_format(uint32_t format)
 	// Bit 3 10 bit - Will assume that begin already cleared it.
 	if (format & 0x08)
 		LPUART0_BAUD |= LPUART_BAUD_M10;
-	
+
+	// 7-bit support
+	if ((format & 0x0E) == 0x02) {
+		data_mask = 0x7f;	// Use only 7 bits of data
+	} else {
+		data_mask = 0x3ff;	// Use only the 10 data bits
+	}
+
 	// Bit 4 RXINVERT 
 	c = LPUART0_STAT & ~LPUART_STAT_RXINV;
 	if (format & 0x10) c |= LPUART_STAT_RXINV;		// rx invert
@@ -456,9 +466,9 @@ void lpuart0_status_isr(void)
 //		if (use9Bits && (UART5_C3 & 0x80)) {
 //			n = UART5_D | 0x100;
 //		} else {
-//			n = UART5_D;
+//			n = UART5_D & data_mask;
 //		}
-		n = LPUART0_DATA & 0x3ff;	// use only the 10 data bits
+		n = LPUART0_DATA & data_mask;
 		head = rx_buffer_head + 1;
 		if (head >= rx_buffer_total_size_) head = 0;
 		if (head != rx_buffer_tail) {