diff --git a/arch/arm/src/kl/kl_idle.c b/arch/arm/src/kl/kl_idle.c
index 8891cf7cbac..6ec2ab46fc2 100644
--- a/arch/arm/src/kl/kl_idle.c
+++ b/arch/arm/src/kl/kl_idle.c
@@ -1,5 +1,5 @@
 /****************************************************************************
- *  arch/arm/src/stm32/kl_idle.c
+ *  arch/arm/src/kl/kl_idle.c
  *
  *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
diff --git a/arch/arm/src/kl/kl_irq.c b/arch/arm/src/kl/kl_irq.c
index 127a667a6ad..4c910a15f83 100644
--- a/arch/arm/src/kl/kl_irq.c
+++ b/arch/arm/src/kl/kl_irq.c
@@ -1,5 +1,5 @@
 /****************************************************************************
- * arch/arm/src/stm32/kl_irq.c
+ * arch/arm/src/kl/kl_irq.c
  *
  *   Copyright (C) 2013-2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
diff --git a/arch/arm/src/kl/kl_irqprio.c b/arch/arm/src/kl/kl_irqprio.c
index 17611aeeabf..a7aba8b8fa6 100644
--- a/arch/arm/src/kl/kl_irqprio.c
+++ b/arch/arm/src/kl/kl_irqprio.c
@@ -1,6 +1,5 @@
 /****************************************************************************
- * arch/arm/src/stm32/kl_irqprio.c
- * arch/arm/src/chip/kl_irqprio.c
+ * arch/arm/src/kl/kl_irqprio.c
  *
  *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
diff --git a/arch/arm/src/kl/kl_pwm.c b/arch/arm/src/kl/kl_pwm.c
index 0b675fe1c9c..df6961ed831 100644
--- a/arch/arm/src/kl/kl_pwm.c
+++ b/arch/arm/src/kl/kl_pwm.c
@@ -693,12 +693,10 @@ static int pwm_ioctl(FAR struct pwm_lowerhalf_s *dev, int cmd, unsigned long arg
  *   Initialize one timer for use with the upper_level PWM driver.
  *
  * Input Parameters:
- *   timer - A number identifying the timer use.  The number of valid timer
- *     IDs varies with the STM32 MCU and MCU family but is somewhere in
- *     the range of {1,..,14}.
+ *   timer - A number identifying the timer use.
  *
  * Returned Value:
- *   On success, a pointer to the STM32 lower half PWM driver is returned.
+ *   On success, a pointer to the KL lower half PWM driver is returned.
  *   NULL is returned on any failure.
  *
  ****************************************************************************/
diff --git a/arch/arm/src/kl/kl_pwm.h b/arch/arm/src/kl/kl_pwm.h
index 104df3bf939..f1544157685 100644
--- a/arch/arm/src/kl/kl_pwm.h
+++ b/arch/arm/src/kl/kl_pwm.h
@@ -77,13 +77,9 @@
  * configuration settings:
  *
  * CONFIG_KL_TPMx_CHANNEL - Specifies the timer output channel {1,..,4}
- * PWM_TPMx_CHn - One of the values defined in chip/stm32*_pinmap.h.  In the case
+ * PWM_TPMx_CHn - One of the values defined in chip/kl*_pinmap.h.  In the case
  *   where there are multiple pin selections, the correct setting must be provided
  *   in the arch/board/board.h file.
- *
- * NOTE: The STM32 timers are each capable of generating different signals on
- * each of the four channels with different duty cycles.  That capability is
- * not supported by this driver:  Only one output channel per timer.
  */
 
 #ifdef CONFIG_KL_TPM0_PWM
@@ -175,12 +171,10 @@ extern "C" {
  *   Initialize one timer for use with the upper_level PWM driver.
  *
  * Input Parameters:
- *   timer - A number identifying the timer use.  The number of valid timer
- *     IDs varies with the STM32 MCU and MCU family but is somewhere in
- *     the range of {1,..,14}.
+ *   timer - A number identifying the timer use.
  *
  * Returned Value:
- *   On success, a pointer to the STM32 lower half PWM driver is returned.
+ *   On success, a pointer to the KL lower half PWM driver is returned.
  *   NULL is returned on any failure.
  *
  ************************************************************************************/
diff --git a/arch/arm/src/samd/Make.defs b/arch/arm/src/samd/Make.defs
index d4ed5f20052..a60ff623e2b 100644
--- a/arch/arm/src/samd/Make.defs
+++ b/arch/arm/src/samd/Make.defs
@@ -75,6 +75,6 @@ ifeq ($(CONFIG_NUTTX_KERNEL),y)
 CHIP_CSRCS += sam_userspace.c
 endif
 
-ifeq ($(CONFIG_NUTTX_KERNEL),y)
+ifeq ($(CONFIG_ARCH_IRQPRIO),y)
 CHIP_CSRCS += sam_irqprio.c
 endif
diff --git a/arch/arm/src/samd/sam_irqprio.c b/arch/arm/src/samd/sam_irqprio.c
index 30046c1a2a1..8948f649201 100644
--- a/arch/arm/src/samd/sam_irqprio.c
+++ b/arch/arm/src/samd/sam_irqprio.c
@@ -1,6 +1,5 @@
 /****************************************************************************
- * arch/arm/src/stm32/kl_irqprio.c
- * arch/arm/src/chip/kl_irqprio.c
+ * arch/arm/src/samd/sam_irqprio.c
  *
  *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
diff --git a/configs/samd20-xplained/include/board.h b/configs/samd20-xplained/include/board.h
index c7956e8ba23..78e30528b83 100644
--- a/configs/samd20-xplained/include/board.h
+++ b/configs/samd20-xplained/include/board.h
@@ -351,17 +351,19 @@
 #define BOARD_FLASH_WAITSTATES       1
 
 /* SERCOM definitions ***************************************************************/
-/* SERCOM4 is available on connectors EXT1 and EXT3
+/* SERCOM4 is available on connectors EXT1, EXT2, and EXT3
  *
- *   PIN   EXT1  EXT3  GPIO  Function
- *   ----  ---- ------ -----------
- *    13   PB09   PB13 SERCOM4 / USART RX
- *    14   PB08   PB12 SERCOM4 / USART TX
- *    19   19          GND
- *    20   20          VCC
+ *   PIN   EXT1 EXT2 EXT3 GPIO Function
+ *   ----  ---- ---- ---- ------------------
+ *    13   PB09 PB13 PB11 SERCOM4 / USART RX
+ *    14   PB08 PB12 PB12 SERCOM4 / USART TX
+ *    19   GND  GND  GND  N/A
+ *    20   VCC  VCC  VCC  N/A
  *
  * If you have a TTL to RS-232 converter then this is the most convenient
- * serial console to use.  It is the default in all of these configurations.
+ * serial console to use (because you don't lose the console device each time
+ * you lose the USB connection).  It is the default in all of the SAMD20
+ * configurations.
  */
 
 #define BOARD_SERCOM4_GCLKGEN        GCLK_CLKCTRL_GEN0