diff --git a/drivers/modem/altair/altmdm_pm.c b/drivers/modem/altair/altmdm_pm.c
index d52f9c4bd1..1268cb309a 100644
--- a/drivers/modem/altair/altmdm_pm.c
+++ b/drivers/modem/altair/altmdm_pm.c
@@ -43,7 +43,9 @@
 #include <errno.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/modem/altmdm.h>
+
 #include "altmdm_sys.h"
 #include "altmdm_pm.h"
 #include "altmdm_pm_state.h"
@@ -1277,7 +1279,8 @@ int altmdm_pm_uninit(FAR struct altmdm_dev_s *priv)
         {
           break;
         }
-      usleep(10);
+
+      nxsig_usleep(10);
     }
 
   /* Delete event flags. */
diff --git a/drivers/modem/altair/altmdm_spi.c b/drivers/modem/altair/altmdm_spi.c
index 2e137fd82d..c3c39807d9 100644
--- a/drivers/modem/altair/altmdm_spi.c
+++ b/drivers/modem/altair/altmdm_spi.c
@@ -41,8 +41,10 @@
 #include <string.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/spi/spi.h>
 #include <nuttx/modem/altmdm.h>
+
 #include "altmdm_sys.h"
 #include "altmdm_pm.h"
 #include "altmdm_pm_state.h"
@@ -1943,7 +1945,7 @@ int altmdm_spi_uninit(FAR struct altmdm_dev_s *priv)
           break;
         }
 
-      usleep(10);
+      nxsig_usleep(10);
     }
 
   altmdm_sys_deletelock(&priv->spidev.tx_param.lock);
@@ -2153,7 +2155,7 @@ again:
           break;
 
         case TRANS_OK_RCVBUFFUL:
-          usleep(100);
+          nxsig_usleep(100);
           goto again;
           break;
 
diff --git a/drivers/mtd/gd25.c b/drivers/mtd/gd25.c
index 0e44fbb5ed..930e57c71c 100644
--- a/drivers/mtd/gd25.c
+++ b/drivers/mtd/gd25.c
@@ -411,7 +411,7 @@ static uint8_t gd25_waitwritecomplete(FAR struct gd25_dev_s *priv)
       if (priv->prev_instr != GD25_PP && (status & GD25_SR_WIP) != 0)
         {
           gd25_unlock(priv->spi);
-          usleep(1000);
+          nxsig_usleep(1000);
           gd25_lock(priv->spi);
         }
     }
diff --git a/drivers/mtd/gd5f.c b/drivers/mtd/gd5f.c
index d4a48c7584..f9ee51c8ea 100644
--- a/drivers/mtd/gd5f.c
+++ b/drivers/mtd/gd5f.c
@@ -49,6 +49,7 @@
 #include <debug.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/fs/ioctl.h>
 #include <nuttx/spi/spi.h>
 #include <nuttx/mtd/mtd.h>
@@ -327,7 +328,7 @@ static bool gd5f_waitstatus(FAR struct gd5f_dev_s *priv, uint8_t mask, bool succ
       /* Deselect the FLASH */
 
       SPI_SELECT(priv->dev, SPIDEV_FLASH(priv->spi_devid), false);
-      usleep(1000);
+      nxsig_usleep(1000);
     }
   while ((status & GD5F_SR_OIP) != 0);
 
diff --git a/drivers/mtd/mx35.c b/drivers/mtd/mx35.c
index b86f55ce75..2f7a4a7ed3 100644
--- a/drivers/mtd/mx35.c
+++ b/drivers/mtd/mx35.c
@@ -2,7 +2,7 @@
  * drivers/mtd/mx35.c
  * Driver for SPI-based MX35LFxGE4AB parts of 1 or 2GBit.
  *
- *   Copyright (C) 2016 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2016, 2019 Gregory Nutt. All rights reserved.
  *   Author: Ekaterina Kovylova <fomalhaut.hm@gmail.com>
  *
  *   Copied from / based on mx25lx.c driver written by
@@ -52,6 +52,7 @@
 #include <debug.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/fs/ioctl.h>
 #include <nuttx/spi/spi.h>
 #include <nuttx/mtd/mtd.h>
@@ -379,7 +380,7 @@ static bool mx35_waitstatus(FAR struct mx35_dev_s *priv, uint8_t mask, bool succ
        * other peripherals to access the SPI bus.
        */
     }
-  while (((status & MX35_SR_OIP) != 0) && (!usleep(1000)));
+  while (((status & MX35_SR_OIP) != 0) && (!nxsig_usleep(1000)));
 
   mx35info("Complete\n");
   return successif ? ((status & mask) != 0) : ((status & mask) == 0);
diff --git a/drivers/sensors/as726x.c b/drivers/sensors/as726x.c
index 1ad92713c5..8b9f62abd6 100644
--- a/drivers/sensors/as726x.c
+++ b/drivers/sensors/as726x.c
@@ -226,7 +226,7 @@ static uint8_t as726x_read8(FAR struct as726x_dev_s *priv, uint8_t regaddr)
           break;  /* If TX bit is clear, it is ok to write */
         }
 
-      usleep(AS726X_POLLING_DELAY);
+      nxsig_usleep(AS726X_POLLING_DELAY);
     }
 
   /* Send the virtual register address (bit 7 should be 0 to indicate we are
@@ -245,7 +245,7 @@ static uint8_t as726x_read8(FAR struct as726x_dev_s *priv, uint8_t regaddr)
           break;  /* Read data is ready. */
         }
 
-      usleep(AS726X_POLLING_DELAY);
+      nxsig_usleep(AS726X_POLLING_DELAY);
     }
 
   uint8_t incoming = read_register(priv, AS72XX_SLAVE_READ_REG);
@@ -300,7 +300,7 @@ static void as726x_write8(FAR struct as726x_dev_s *priv, uint8_t regaddr,
           break;
         }
 
-      usleep(AS726X_POLLING_DELAY);
+      nxsig_usleep(AS726X_POLLING_DELAY);
     }
 
   /* Send the virtual register address (setting bit 7 to indicate we are
@@ -321,7 +321,7 @@ static void as726x_write8(FAR struct as726x_dev_s *priv, uint8_t regaddr,
           break;
         }
 
-      usleep(AS726X_POLLING_DELAY);
+      nxsig_usleep(AS726X_POLLING_DELAY);
     }
 
   /* Send the data to complete the operation. */
diff --git a/drivers/sensors/hts221.c b/drivers/sensors/hts221.c
index 8fd4c17c27..be6297ef7d 100644
--- a/drivers/sensors/hts221.c
+++ b/drivers/sensors/hts221.c
@@ -37,16 +37,19 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
 #include <debug.h>
 #include <stdio.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <errno.h>
+
 #include <nuttx/arch.h>
 #include <nuttx/i2c/i2c_master.h>
 #include <nuttx/irq.h>
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/random.h>
 
 #include <nuttx/sensors/hts221.h>
@@ -400,7 +403,7 @@ static int hts221_config_ctrl_reg2(FAR struct hts221_dev_s *priv,
               break;
             }
 
-          usleep(10 * 1000);
+          nxsig_usleep(10 * 1000);
           retries--;
         }
       while (retries);
diff --git a/drivers/usbdev/usbmsc_scsi.c b/drivers/usbdev/usbmsc_scsi.c
index 369d926be1..9ee740a32a 100644
--- a/drivers/usbdev/usbmsc_scsi.c
+++ b/drivers/usbdev/usbmsc_scsi.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * drivers/usbdev/usbmsc_scsi.c
  *
- *   Copyright (C) 2008-2010, 2012, 2016-2017 Gregory Nutt. All rights
+ *   Copyright (C) 2008-2010, 2012, 2016-2017, 2019 Gregory Nutt. All rights
  *     reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
@@ -71,6 +71,7 @@
 #include <nuttx/irq.h>
 #include <nuttx/kthread.h>
 #include <nuttx/arch.h>
+#include <nuttx/signal.h>
 #include <nuttx/scsi.h>
 #include <nuttx/usb/storage.h>
 #include <nuttx/usb/usbdev.h>
@@ -2467,12 +2468,12 @@ static int usbmsc_cmdfinishstate(FAR struct usbmsc_dev_s *priv)
                * First, wait for the transfer to complete, then stall the endpoint
                */
 
-              usleep (100000);
+              nxsig_usleep (100000);
               (void)EP_STALL(priv->epbulkin);
 
               /* now wait for stall to go away .... */
 
-              usleep (100000);
+              nxsig_usleep (100000);
 #else
               (void)EP_STALL(priv->epbulkin);
 #endif
diff --git a/drivers/usbhost/usbhost_max3421e.c b/drivers/usbhost/usbhost_max3421e.c
index 822069ec76..4202e9a5c4 100644
--- a/drivers/usbhost/usbhost_max3421e.c
+++ b/drivers/usbhost/usbhost_max3421e.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * drivers/usbhost/usbhost_max3421e.c
  *
- *   Copyright (C) 2018 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2018, 2019 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * References:
@@ -3295,7 +3295,7 @@ static void max3421e_int_wait(FAR struct max3421e_usbhost_s *priv,
 
       if (regval == 0 && usec > 0)
         {
-          usleep(usec);
+          nxsig_usleep(usec);
         }
     }
   while (regval == 0);
@@ -4510,7 +4510,7 @@ static int max3421e_startsof(FAR struct max3421e_usbhost_s *priv)
   while ((max3421e_getreg(priv, MAX3421E_USBHOST_HCTL) &
           USBHOST_HCTL_BUSSAMPLE) == 0)
     {
-      usleep(5);
+      nxsig_usleep(5);
     }
 
   /* Check for low- or full-speed and start SOF (actually already started
@@ -4579,7 +4579,7 @@ static int max3421e_startsof(FAR struct max3421e_usbhost_s *priv)
  /* Wait for the first SOF received and 20ms has passed */
 
   max3421e_int_wait(priv, USBHOST_HIRQ_FRAMEIRQ, 0);
-  usleep(20*1000);
+  nxsig_usleep(20*1000);
   return OK;
 }
 
diff --git a/drivers/video/isx012.c b/drivers/video/isx012.c
index 981bc8988a..bc316e9def 100644
--- a/drivers/video/isx012.c
+++ b/drivers/video/isx012.c
@@ -45,6 +45,7 @@
 #include <debug.h>
 
 #include <nuttx/arch.h>
+#include <nuttx/signal.h>
 #include <nuttx/fs/fs.h>
 #include <nuttx/i2c/i2c_master.h>
 #include <arch/board/board.h>
@@ -741,7 +742,7 @@ static int isx012_chk_int_state(isx012_dev_t *priv,
   volatile uint8_t data;
   uint32_t time = 0;
 
-  usleep(delay_time * 1000);
+  nxsig_usleep(delay_time * 1000);
   while (time < timeout)
     {
       data = isx012_getreg(priv, INTSTS0, sizeof(data));
@@ -752,7 +753,7 @@ static int isx012_chk_int_state(isx012_dev_t *priv,
           return ret;
         }
 
-      usleep(wait_time * 1000);
+      nxsig_usleep(wait_time * 1000);
       time += wait_time;
     }
   return ERROR;
@@ -1107,10 +1108,10 @@ int init_isx012(FAR struct isx012_dev_s *priv)
 #ifdef ISX012_NOT_USE_NSTBY
   board_isx012_release_sleep();
   board_isx012_release_reset();
-  usleep(6000);
+  nxsig_usleep(6000);
 #else
   board_isx012_release_reset();
-  usleep(6000);
+  nxsig_usleep(6000);
 #endif
 
 #ifdef ISX012_CHECK_IN_DETAIL
diff --git a/drivers/wireless/cc1101.c b/drivers/wireless/cc1101.c
index 44d5618cb8..92e45f9455 100644
--- a/drivers/wireless/cc1101.c
+++ b/drivers/wireless/cc1101.c
@@ -111,6 +111,7 @@
 #include <debug.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/fs/fs.h>
 #include <nuttx/wireless/cc1101.h>
 
@@ -720,7 +721,7 @@ void cc1101_access_begin(FAR struct cc1101_dev_s *dev)
     }
   else
     {
-      usleep(150 * 1000);
+      nxsig_usleep(150 * 1000);
     }
 }
 
diff --git a/drivers/wireless/gs2200m.c b/drivers/wireless/gs2200m.c
index 8c69927177..88f9a78807 100644
--- a/drivers/wireless/gs2200m.c
+++ b/drivers/wireless/gs2200m.c
@@ -55,6 +55,7 @@
 #include <nuttx/kmalloc.h>
 #include <nuttx/wqueue.h>
 #include <nuttx/semaphore.h>
+#include <nuttx/signal.h>
 #include <nuttx/wireless/gs2200m.h>
 #include <nuttx/net/netdev.h>
 
@@ -878,14 +879,14 @@ retry:
     {
       /* TODO: timeout */
 
-      usleep(10);
+      nxsig_usleep(10);
     }
 
   /* NOTE: wait 100us
-   * workaround to avoid realy receiving an invalid frame response
+   * workaround to avoid really receiving an invalid frame response
    */
 
-  up_udelay(100);
+  nxsig_usleep(100);
 
   /* Read frame response */
 
diff --git a/drivers/wireless/ieee80211/bcm43xxx/bcmf_driver.c b/drivers/wireless/ieee80211/bcm43xxx/bcmf_driver.c
index e4504c6076..6c3fb0e007 100644
--- a/drivers/wireless/ieee80211/bcm43xxx/bcmf_driver.c
+++ b/drivers/wireless/ieee80211/bcm43xxx/bcmf_driver.c
@@ -50,6 +50,7 @@
 #include <net/ethernet.h>
 
 #include <nuttx/kmalloc.h>
+#include <nuttx/signal.h>
 #include <nuttx/wdog.h>
 #include <nuttx/sdio.h>
 #include <nuttx/net/arp.h>
@@ -995,7 +996,7 @@ int bcmf_wl_enable(FAR struct bcmf_dev_s *priv, bool enable)
 
   /* TODO wait for WLC_E_RADIO event */
 
-  usleep(3000);
+  nxsig_usleep(3000);
 
   if (ret == OK)
     {
diff --git a/drivers/wireless/lpwan/sx127x/sx127x.c b/drivers/wireless/lpwan/sx127x/sx127x.c
index a60271e03f..737fa45727 100644
--- a/drivers/wireless/lpwan/sx127x/sx127x.c
+++ b/drivers/wireless/lpwan/sx127x/sx127x.c
@@ -2977,7 +2977,7 @@ static int sx127x_lora_opmode_set(FAR struct sx127x_dev_s *dev,
 
   /* Wait for mode ready. REVISIT: do we need this ? */
 
-  usleep(250);
+  nxsig_usleep(250);
 
 errout:
   return ret;
@@ -3805,7 +3805,7 @@ static bool sx127x_channel_scan(FAR struct sx127x_dev_s *dev,
 
       /* Wait some time */
 
-      usleep(1000);
+      nxsig_usleep(1000);
     }
   while (tstart.tv_sec + chanscan->stime > tnow.tv_sec);
 
@@ -4160,7 +4160,7 @@ static int sx127x_calibration(FAR struct sx127x_dev_s *dev, uint32_t freq)
     {
       /* Wait 10ms */
 
-      usleep(10000);
+      nxsig_usleep(10000);
 
       /* Get register */