diff --git a/Documentation/NuttX.html b/Documentation/NuttX.html
index a15f971a18e..e3a052f22fe 100644
--- a/Documentation/NuttX.html
+++ b/Documentation/NuttX.html
@@ -7237,12 +7237,15 @@ if [ -x "$WINELOADER" ]; then exec "$WINELOADER" "$appname" "$@"; fi
   <li>NuttX is a registered trademark of Gregory Nutt.</li>
   <li>ARM, ARM7 ARM7TDMI, ARM9, ARM920T, ARM926EJS, Cortex-M3 are trademarks of Advanced RISC Machines, Limited.</li>
   <li>Beaglebone is a trademark of GHI.</li>
+  <li>BSD is a trademark of the University of California, Berkeley, USA.</li>
   <li>Cygwin is a trademark of Red Hat, Incorporated.</li>
   <li>Linux is a registered trademark of Linus Torvalds.</li>
   <li>Eagle-100 is a trademark of <a href=" http://www.micromint.com/">Micromint USA, LLC</a>.
   <li>EnergyLite is a trademark of STMicroelectronics.</li>
   <li>EFM32 is a trademark of Silicon Laboratories, Inc.</li>
   <li>LPC2148 is a trademark of NXP Semiconductors.</li>
+  <li>POSIX is a trademark of the Institute of Electrical and Electronic Engineers, Inc.</li>
+  <li>RISC-V is a registration pending trade mark of the RISC-V Foundation.</li>
   <li>Sitara is a trademark of Texas Instruments Incorporated.</li>
   <li>TI is a tradename of Texas Instruments Incorporated.</li>
   <li>Tiva is a trademark of Texas Instruments Incorporated.</li>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 9b31921f210..caa37325365 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -406,3 +406,13 @@ menuconfig SPECIFIC_DRIVERS
 if SPECIFIC_DRIVERS
 source drivers/platform/Kconfig
 endif # SPECIFIC_DRIVERS
+
+menuconfig DRIVERS_RF
+	bool "RF Device Support"
+	default n
+	---help---
+		Drivers for various RF devices
+
+if DRIVERS_RF
+source drivers/rf/Kconfig
+endif # DRIVERS_RF
diff --git a/drivers/Makefile b/drivers/Makefile
index bdce6ae7ae0..0edbb7ac63e 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -81,6 +81,7 @@ include video$(DELIM)Make.defs
 include wireless$(DELIM)Make.defs
 include contactless$(DELIM)Make.defs
 include 1wire$(DELIM)Make.defs
+include rf$(DELIM)Make.defs
 
 ifeq ($(CONFIG_SPECIFIC_DRIVERS),y)
 include platform$(DELIM)Make.defs
diff --git a/drivers/rf/Kconfig b/drivers/rf/Kconfig
new file mode 100644
index 00000000000..34fcd8c224b
--- /dev/null
+++ b/drivers/rf/Kconfig
@@ -0,0 +1,12 @@
+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config RF_DAT31R5SP
+	bool "Mini-Circuits DAT-31R5-SP digital attenuator support"
+	default n
+	select SPI
+	---help---
+		Enable driver support for the Mini-Circuits DAT-31R5-SP digital
+		attenuator.
diff --git a/drivers/rf/Make.defs b/drivers/rf/Make.defs
new file mode 100644
index 00000000000..1103801f2ab
--- /dev/null
+++ b/drivers/rf/Make.defs
@@ -0,0 +1,57 @@
+############################################################################
+# drivers/rf/Make.defs
+#
+#   Copyright (C) 2011-2012, 2015-2018 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2019 Augusto Fraga Giachero. All rights reserved.
+#   Author: Augusto Fraga Giachero <afg@augustofg.net>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name NuttX nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+
+# Include rf drivers
+
+RFDEPPATH =
+RFVPATH =
+
+ifeq ($(CONFIG_DRIVERS_RF),y)
+
+ifeq ($(CONFIG_SPI),y)
+
+ifeq ($(CONFIG_RF_DAT31R5SP),y)
+  CSRCS += dat-31r5-sp.c
+  RFDEPPATH = --dep-path rf
+  RFVPATH = :rf
+endif
+
+endif # CONFIG_SPI
+
+endif # CONFIG_DRIVERS_RF
+
+DEPPATH += $(RFDEPPATH)
+VPATH += $(RFVPATH)
diff --git a/drivers/rf/dat-31r5-sp.c b/drivers/rf/dat-31r5-sp.c
new file mode 100644
index 00000000000..bc31b77da9f
--- /dev/null
+++ b/drivers/rf/dat-31r5-sp.c
@@ -0,0 +1,298 @@
+/****************************************************************************
+ * drivers/rf/dat-31r5-sp.c
+ * Character driver for the Mini-Circuits DAT-31R5-SP+ digital step
+ * attenuator.
+ *
+ *   Copyright (C) 2019, Augusto Fraga Giachero. All rights reserved.
+ *   Author: Augusto Fraga Giachero <afg@augustofg.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdlib.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/fs/fs.h>
+#include <nuttx/spi/spi.h>
+#include <nuttx/rf/ioctl.h>
+#include <nuttx/rf/attenuator.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#if defined(CONFIG_SPI) && defined(CONFIG_RF_DAT31R5SP)
+
+#ifndef CONFIG_DAT31R5SP_SPI_FREQUENCY
+#  define CONFIG_DAT31R5SP_SPI_FREQUENCY 1000000
+#endif
+
+#define DAT31R5SP_SPI_MODE (SPIDEV_MODE0) /* SPI Mode 0: CPOL=0,CPHA=0 */
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct dat31r5sp_dev_s
+{
+  FAR struct spi_dev_s *spi;    /* Saved SPI driver instance */
+  int spidev;
+};
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* Character driver methods */
+
+static int dat31r5sp_open(FAR struct file *filep);
+static int dat31r5sp_close(FAR struct file *filep);
+static ssize_t dat31r5sp_read(FAR struct file *filep, FAR char *buffer,
+                              size_t buflen);
+static ssize_t dat31r5sp_write(FAR struct file *filep,
+                               FAR const char *buffer, size_t buflen);
+static int dat31r5sp_ioctl(FAR struct file *filep, int cmd,
+                           unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations g_dat31r5sp_fops =
+{
+  dat31r5sp_open,
+  dat31r5sp_close,
+  dat31r5sp_read,
+  dat31r5sp_write,
+  NULL,
+  dat31r5sp_ioctl,
+  NULL
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: dat31r5sp_configspi
+ *
+ * Description:
+ *   Configure the SPI instance for to match the DAT-31R5-SP+
+ *   specifications
+ *
+ ****************************************************************************/
+
+static inline void dat31r5sp_configspi(FAR struct spi_dev_s *spi)
+{
+  SPI_SETMODE(spi, DAT31R5SP_SPI_MODE);
+  SPI_SETBITS(spi, 8);
+  SPI_HWFEATURES(spi, 0);
+  SPI_SETFREQUENCY(spi, CONFIG_DAT31R5SP_SPI_FREQUENCY);
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_set_attenuation
+ *
+ * Description:
+ *   Set the attenuation level in dB (16.16 bits fixed point).
+ *
+ ****************************************************************************/
+
+static void dat31r5sp_set_attenuation(FAR struct dat31r5sp_dev_s *priv,
+                                      b16_t attenuation)
+{
+  SPI_LOCK(priv->spi, true);
+
+  dat31r5sp_configspi(priv->spi);
+
+  SPI_SELECT(priv->spi, priv->spidev, false);
+
+  /* Convert the attenuation value from 16.16 bits to 5.1 bits. */
+
+  SPI_SEND(priv->spi, (uint8_t)(attenuation >> 15));
+
+  /* Send a pulse to the LE pin */
+
+  SPI_SELECT(priv->spi, priv->spidev, true);
+  up_udelay(1);
+  SPI_SELECT(priv->spi, priv->spidev, false);
+
+  SPI_LOCK(priv->spi, false);
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_open
+ *
+ * Description:
+ *   This function is called whenever the DAT-31R5-SP+ device is
+ *   opened.
+ *
+ ****************************************************************************/
+
+static int dat31r5sp_open(FAR struct file *filep)
+{
+  return OK;
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_close
+ *
+ * Description:
+ *   This function is called whenever the DAT-31R5-SP+ device is
+ *   closed.
+ *
+ ****************************************************************************/
+
+static int dat31r5sp_close(FAR struct file *filep)
+{
+  return OK;
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_write
+ *
+ * Description:
+ *   Write is not permited, only IOCTLs.
+ ****************************************************************************/
+
+static ssize_t dat31r5sp_write(FAR struct file *filep, FAR const char *buffer,
+                               size_t buflen)
+{
+  return -ENOSYS;
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_read
+ *
+ * Description:
+ *   Read is ignored.
+ ****************************************************************************/
+
+static ssize_t dat31r5sp_read(FAR struct file *filep, FAR char *buffer,
+                              size_t buflen)
+{
+  return 0;
+}
+
+/****************************************************************************
+ * Name: dat31r5sp_ioctl
+ *
+ * Description:
+ *   The only available ICTL is RFIOC_SETATT. It expects a struct
+ *   attenuator_control* as the argument to set the attenuation
+ *   level. The channel is ignored as the DAT-31R5-SP+ has just a
+ *   single attenuator.
+ ****************************************************************************/
+
+static int dat31r5sp_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
+{
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct dat31r5sp_dev_s *priv = inode->i_private;
+  int ret = OK;
+
+  switch (cmd)
+    {
+      case RFIOC_SETATT:
+        {
+          FAR struct attenuator_control *att =
+            (FAR struct attenuator_control *)((uintptr_t)arg);
+          DEBUGASSERT(ptr != NULL);
+          dat31r5sp_set_attenuation(priv, att->attenuation);
+        }
+        break;
+
+      default:
+        sninfo("Unrecognized cmd: %d\n", cmd);
+        ret = -ENOTTY;
+        break;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: dat31r5sp_register
+ *
+ * Description:
+ *   Register the dat31r5sp character device as 'devpath'.
+ *
+ ****************************************************************************/
+
+int dat31r5sp_register(FAR const char *devpath,
+                       FAR struct spi_dev_s *spi,
+                       int spidev)
+{
+  FAR struct dat31r5sp_dev_s *priv;
+  int ret;
+
+  /* Sanity check */
+
+  DEBUGASSERT(spi != NULL);
+
+  /* Initialize the DAT-31R5-SP+ device structure */
+
+  priv = (FAR struct dat31r5sp_dev_s *)kmm_malloc(sizeof(struct dat31r5sp_dev_s));
+  if (priv == NULL)
+    {
+      snerr("ERROR: Failed to allocate instance\n");
+      return -ENOMEM;
+    }
+
+  priv->spi    = spi;
+  priv->spidev = spidev;
+
+  /* Clear the LE pin */
+
+  SPI_SELECT(priv->spi, priv->spidev, false);
+
+  /* Register the character driver */
+
+  ret = register_driver(devpath, &g_dat31r5sp_fops, 0666, priv);
+  if (ret < 0)
+    {
+      snerr("ERROR: Failed to register driver: %d\n", ret);
+      kmm_free(priv);
+    }
+
+  return ret;
+}
+
+#endif
diff --git a/include/nuttx/fs/ioctl.h b/include/nuttx/fs/ioctl.h
index 8c3db1f4235..46e8ae89ce7 100644
--- a/include/nuttx/fs/ioctl.h
+++ b/include/nuttx/fs/ioctl.h
@@ -48,6 +48,7 @@
  ****************************************************************************/
 
 /* General ioctl definitions ************************************************/
+
 /* Each NuttX ioctl commands are uint16_t's consisting of an 8-bit type
  * identifier and an 8-bit command number.  All command type identifiers are
  * defined below:
@@ -94,6 +95,7 @@
 #define _PWRBASE        (0x2700) /* Power-related ioctl commands */
 #define _FBIOCBASE      (0x2800) /* Frame buffer character driver ioctl commands */
 #define _NXTERMBASE     (0x2900) /* NxTerm character driver ioctl commands */
+#define _RFIOCBASE      (0x2a00) /* RF devices ioctl commands */
 
 /* boardctl() commands share the same number space */
 
@@ -143,8 +145,8 @@
                                            */
 #define FIOC_FILENAME   _FIOC(0x0004)     /* IN:  FAR const char ** pointer
                                            * OUT: Pointer to a persistent file name
-                                           *      (Guaranteed to persist while the file
-                                           *      is open).
+                                           *      (Guaranteed to persist while the
+                                           *      file is open).
                                            */
 #define FIOC_INTEGRITY  _FIOC(0x0005)     /* Run a consistency check on the
                                            *      file system media.
@@ -197,7 +199,7 @@
                                            * IN:  Pointer to pointer to void in
                                            *      which to received the XIP base.
                                            * OUT: If media is directly accessible,
-                                           *      return (void*) base address
+                                           *      return (void *) base address
                                            *      of device memory */
 #define BIOC_PROBE      _BIOC(0x0002)     /* Re-probe and interface; check for media
                                            * in the slot
@@ -269,6 +271,7 @@
 #define _MTDIOC(nr)       _IOC(_MTDIOCBASE,nr)
 
 /* Socket IOCTLs ************************************************************/
+
 /* See include/nuttx/net/ioctl.h */
 
 #define _SIOCVALID(c)    (_IOC_TYPE(c)==_SIOCBASE)
@@ -306,6 +309,7 @@
 #define _CAIOC(nr)        _IOC(_CAIOCBASE,nr)
 
 /* NuttX USB CDC/ACM serial driver ioctl definitions ************************/
+
 /* (see nuttx/power/battery.h) */
 
 #define _BATIOCVALID(c)   (_IOC_TYPE(c)==_BATIOCBASE)
@@ -318,24 +322,28 @@
 #define _QEIOC(nr)        _IOC(_QEIOCBASE,nr)
 
 /* NuttX Audio driver ioctl definitions *************************************/
+
 /* (see nuttx/audio/audio.h) */
 
 #define _AUDIOIOCVALID(c) (_IOC_TYPE(c)==_AUDIOIOCBASE)
 #define _AUDIOIOC(nr)     _IOC(_AUDIOIOCBASE,nr)
 
 /* LCD character driver ioctl definitions ***********************************/
+
 /* (see nuttx/include/lcd/slcd_codec.h */
 
 #define _LCDIOCVALID(c)   (_IOC_TYPE(c)==_LCDIOCBASE)
 #define _LCDIOC(nr)       _IOC(_LCDIOCBASE,nr)
 
 /* Segment LCD driver ioctl definitions *************************************/
+
 /* (see nuttx/include/lcd/slcd_codec.h */
 
 #define _SLCDIOCVALID(c)  (_IOC_TYPE(c)==_SLCDIOCBASE)
 #define _SLCDIOC(nr)      _IOC(_SLCDIOCBASE,nr)
 
 /* Wireless driver networki ioctl definitions *******************************/
+
 /* (see nuttx/include/wireless/wireless.h */
 
 #define _WLIOCVALID(c)    (_IOC_TYPE(c)==_WLIOCBASE)
@@ -348,18 +356,21 @@
 #define _WLCIOC(nr)       _IOC(_WLCIOCBASE,nr)
 
 /* Application Config Data driver ioctl definitions *************************/
+
 /* (see nuttx/include/configdata.h */
 
 #define _CFGDIOCVALID(c)  (_IOC_TYPE(c)==_CFGDIOCBASE)
 #define _CFGDIOC(nr)      _IOC(_CFGDIOCBASE,nr)
 
 /* Timer driver ioctl commands **********************************************/
+
 /* (see nuttx/include/timer.h */
 
 #define _TCIOCVALID(c)    (_IOC_TYPE(c)==_TCIOCBASE)
 #define _TCIOC(nr)        _IOC(_TCIOCBASE,nr)
 
 /* Joystick driver ioctl definitions ***************************************/
+
 /* Discrete Joystick (see nuttx/include/input/djoystick.h */
 
 #define _JOYIOCVALID(c)   (_IOC_SMASK(c)==_JOYBASE)
@@ -378,84 +389,98 @@
                                              * OUT: None */
 
 /* RTC driver ioctl definitions *********************************************/
+
 /* (see nuttx/include/rtc.h */
 
 #define _RTCIOCVALID(c)   (_IOC_TYPE(c)==_RTCBASE)
 #define _RTCIOC(nr)       _IOC(_RTCBASE,nr)
 
 /* Relay driver ioctl definitions *******************************************/
+
 /* (see nuttx/power/relay.h */
 
 #define _RELAYIOCVALID(c) (_IOC_TYPE(c)==_RELAYBASE)
 #define _RELAYIOC(nr)     _IOC(_RELAYBASE,nr)
 
 /* CAN driver ioctl definitions *********************************************/
+
 /* (see nuttx/can/can.h */
 
 #define _CANIOCVALID(c)   (_IOC_TYPE(c)==_CANBASE)
 #define _CANIOC(nr)       _IOC(_CANBASE,nr)
 
 /* Button driver ioctl definitions ******************************************/
+
 /* (see nuttx/input/buttons.h */
 
 #define _BTNIOCVALID(c)   (_IOC_TYPE(c)==_BTNBASE)
 #define _BTNIOC(nr)       _IOC(_BTNBASE,nr)
 
 /* User LED driver ioctl definitions ****************************************/
+
 /* (see nuttx/leds/usersled.h */
 
 #define _ULEDIOCVALID(c)  (_IOC_TYPE(c)==_ULEDBASE)
 #define _ULEDIOC(nr)      _IOC(_ULEDBASE,nr)
 
 /* Zero Cross driver ioctl definitions **************************************/
+
 /* (see nuttx/include/sensor/zerocross.h */
 
 #define _ZCIOCVALID(c)    (_IOC_TYPE(c)==_ZCBASE)
 #define _ZCIOC(nr)        _IOC(_ZCBASE,nr)
 
 /* Loop driver ioctl definitions ********************************************/
+
 /* (see nuttx/include/fs/loop.h */
 
 #define _LOOPIOCVALID(c)  (_IOC_TYPE(c)==_LOOPBASE)
 #define _LOOPIOC(nr)      _IOC(_LOOPBASE,nr)
 
 /* Modem driver ioctl definitions *******************************************/
+
 /* see nuttx/include/modem/ioctl.h */
 
 #define _MODEMIOCVALID(c) (_IOC_TYPE(c)==_MODEMBASE)
 #define _MODEMIOC(nr)     _IOC(_MODEMBASE,nr)
 
 /* I2C driver ioctl definitions *********************************************/
+
 /* see nuttx/include/i2c/i2c_master.h */
 
 #define _I2CIOCVALID(c)   (_IOC_TYPE(c)==_I2CBASE)
 #define _I2CIOC(nr)       _IOC(_I2CBASE,nr)
 
 /* SPI driver ioctl definitions *********************************************/
+
 /* see nuttx/include/spi/spi_transfer.h */
 
 #define _SPIIOCVALID(c)   (_IOC_TYPE(c)==_SPIBASE)
 #define _SPIIOC(nr)       _IOC(_SPIBASE,nr)
 
 /* GPIO driver command definitions ******************************************/
+
 /* see nuttx/include/ioexpander/gpio.h */
 
 #define _GPIOCVALID(c)    (_IOC_TYPE(c)==_GPIOBASE)
 #define _GPIOC(nr)        _IOC(_GPIOBASE,nr)
 
 /* Contactless driver ioctl definitions *************************************/
+
 /* (see nuttx/include/contactless/ioctl.h */
 
 #define _CLIOCVALID(c)    (_IOC_TYPE(c)==_CLIOCBASE)
 #define _CLIOC(nr)        _IOC(_CLIOCBASE,nr)
 
 /* USB-C controller driver ioctl definitions ********************************/
+
 /* (see nuttx/include/usb/xxx.h */
 
 #define _USBCIOCVALID(c)  (_IOC_TYPE(c)==_USBCBASE)
 #define _USBCIOC(nr)      _IOC(_USBCBASE,nr)
 
 /* 802.15.4 MAC driver ioctl definitions ************************************/
+
 /* (see nuttx/include/wireless/ieee802154/ieee802154_mac.h */
 
 #define _MAC802154IOCVALID(c)  (_IOC_TYPE(c)==_MAC802154BASE)
@@ -476,6 +501,11 @@
 #define _NXTERMVALID(c)   (_IOC_TYPE(c)==_NXTERMBASE)
 #define _NXTERMIOC(nr)    _IOC(_NXTERMBASE,nr)
 
+/* NuttX RF ioctl definitions (see nuttx/rf/ioctl.h) ************************/
+
+#define _RFIOCVALID(c)    (_IOC_TYPE(c)==_RFIOCBASE)
+#define _RFIOC(nr)        _IOC(_RFIOCBASE,nr)
+
 /* boardctl() command definitions *******************************************/
 
 #define _BOARDIOCVALID(c) (_IOC_TYPE(c)==_BOARDBASE)
diff --git a/include/nuttx/rf/attenuator.h b/include/nuttx/rf/attenuator.h
new file mode 100644
index 00000000000..848921d0d43
--- /dev/null
+++ b/include/nuttx/rf/attenuator.h
@@ -0,0 +1,68 @@
+/****************************************************************************
+ * include/nuttx/rf/attenuator.h
+ *
+ *   Copyright (C) 2019, Augusto Fraga Giachero. All rights reserved.
+ *   Author: Augusto Fraga Giachero <afg@augustofg.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_RF_ATTENUATOR_H
+#define __INCLUDE_NUTTX_RF_ATTENUATOR_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <fixedmath.h>
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Public Type Definitions
+ ****************************************************************************/
+
+struct attenuator_control
+{
+  b16_t attenuation;
+  int channel;
+};
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __INCLUDE_NUTTX_RF_ATTENUATOR_H */
diff --git a/include/nuttx/rf/dat-31r5-sp.h b/include/nuttx/rf/dat-31r5-sp.h
new file mode 100644
index 00000000000..c3a4b6d8f59
--- /dev/null
+++ b/include/nuttx/rf/dat-31r5-sp.h
@@ -0,0 +1,99 @@
+/****************************************************************************
+ * include/nuttx/rf/dat-31r5-sp.h
+ * Character driver for the Mini-Circuits DAT-31R5-SP+ digital step
+ * attenuator.
+ *
+ *   Copyright (C) 2019, Augusto Fraga Giachero. All rights reserved.
+ *   Author: Augusto Fraga Giachero <afg@augustofg.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_RF_DAT_31R5_SP_H_
+#define __INCLUDE_NUTTX_RF_DAT_31R5_SP_H_
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/irq.h>
+#include <nuttx/config.h>
+#include <nuttx/rf/ioctl.h>
+#include <nuttx/spi/spi.h>
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+#ifdef __cplusplus
+#define EXTERN extern "C"
+extern "C"
+{
+#else
+#define EXTERN extern
+#endif
+
+/****************************************************************************
+ * Name: dat31r5sp_register
+ *
+ * Description:
+ *   Register the dat31r5sp character device as 'devpath'. WARNING:
+ *   the DAT-31R5-SP+ is not spi compatible because it hasn't a proper
+ *   chip-select input, but it can coexist with other devices on the
+ *   spi bus assuming that the LE (Latch Enable) is always 0 when the
+ *   device isn't selected. With LE=0 the internal shift-register will
+ *   store the last 6 bits sent through the bus, but it will only
+ *   change the attenuation level when LE=1. This driver sends the
+ *   attenuation bitstream and gives a small positive pulse to LE.
+ *
+ *   Remember when implementing the corresponding spi select function
+ *   when selected == true LE should be 1, and when selected == false
+ *   LE should be 0.
+ *
+ * Input Parameters:
+ *   devpath - The full path to the driver to register. E.g., "/dev/att0"
+ *   spi     - An instance of the SPI interface to use to communicate with
+ *   spidev  - Number of the spi device (used to drive the Latch Enable pin).
+ *
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int dat31r5sp_register(FAR const char *devpath,
+                       FAR struct spi_dev_s *spi,
+                       int spidev);
+
+#undef EXTERN
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __INCLUDE_NUTTX_RF_DAT_31R5_SP_H_ */
diff --git a/include/nuttx/rf/ioctl.h b/include/nuttx/rf/ioctl.h
new file mode 100644
index 00000000000..bbbf8e4dd6e
--- /dev/null
+++ b/include/nuttx/rf/ioctl.h
@@ -0,0 +1,46 @@
+/****************************************************************************
+ * include/nuttx/rf/ioctl.h
+ *
+ *   Copyright (C) 2019, Augusto Fraga Giachero. All rights reserved.
+ *   Author: Augusto Fraga Giachero <afg@augustofg.net>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_NUTTX_RF_IOCTL_H
+#define __INCLUDE_NUTTX_RF_IOCTL_H
+
+#include <nuttx/config.h>
+#include <nuttx/fs/ioctl.h>
+
+/* Generic IOCTLs commands used for digital attenuators */
+
+#define RFIOC_SETATT                        _RFIOC(0x0001) /* Set the attenuation, Arg: struct attenuator_control* */
+
+#endif