0001-RS-485-support-for-STM32-serial-driver.patch from Freddi Chopin

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5371 42af7a65-404d-4744-a932-0658087f49c3

5 files changed, 329 insertions, 11 deletions

diff --git a/nuttx/arch/arm/src/stm32/Kconfig b/nuttx/arch/arm/src/stm32/Kconfig
index 81ba9e4a3..68cd9003c 100644
--- a/nuttx/arch/arm/src/stm32/Kconfig
+++ b/nuttx/arch/arm/src/stm32/Kconfig
@@ -1831,6 +1831,27 @@ config STM32_TIM14_DAC2
 
 endchoice
 
+menu "U[S]ART Configuration"
+	depends on STM32_USART1 || STM32_USART2 || STM32_USART3 || STM32_USART4 || STM32_USART5 || STM32_USART6
+
+config USART1_RS485
+	bool "RS-485 on USART1"
+	default n
+	depends on STM32_USART1
+	---help---
+		Enable RS-485 interface on USART1. Your board config will have to
+		provide GPIO_USART1_RS485_DIR pin definition. Currently it cannot be
+		used with USART1_RXDMA.
+
+config USART1_RS485_DIR_POLARITY
+	int "USART1 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on USART1_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on USART1. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).		
+
 config USART1_RXDMA
 	bool "USART1 Rx DMA"
 	default n
@@ -1838,6 +1859,24 @@ config USART1_RXDMA
 	---help---
 		In high data rate usage, Rx DMA may eliminate Rx overrun errors
 
+config USART2_RS485
+	bool "RS-485 on USART2"
+	default n
+	depends on STM32_USART2
+	---help---
+		Enable RS-485 interface on USART2. Your board config will have to
+		provide GPIO_USART2_RS485_DIR pin definition. Currently it cannot be
+		used with USART2_RXDMA.
+
+config USART2_RS485_DIR_POLARITY
+	int "USART2 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on USART2_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on USART2. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).
+
 config USART2_RXDMA
 	bool "USART2 Rx DMA"
 	default n
@@ -1845,6 +1884,24 @@ config USART2_RXDMA
 	---help---
 		In high data rate usage, Rx DMA may eliminate Rx overrun errors
 
+config USART3_RS485
+	bool "RS-485 on USART3"
+	default n
+	depends on STM32_USART3
+	---help---
+		Enable RS-485 interface on USART3. Your board config will have to
+		provide GPIO_USART3_RS485_DIR pin definition. Currently it cannot be
+		used with USART3_RXDMA.
+
+config USART3_RS485_DIR_POLARITY
+	int "USART3 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on USART3_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on USART3. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).
+
 config USART3_RXDMA
 	bool "USART3 Rx DMA"
 	default n
@@ -1852,6 +1909,24 @@ config USART3_RXDMA
 	---help---
 		In high data rate usage, Rx DMA may eliminate Rx overrun errors
 
+config UART4_RS485
+	bool "RS-485 on UART4"
+	default n
+	depends on STM32_UART4
+	---help---
+		Enable RS-485 interface on UART4. Your board config will have to
+		provide GPIO_UART4_RS485_DIR pin definition. Currently it cannot be
+		used with UART4_RXDMA.
+
+config UART4_RS485_DIR_POLARITY
+	int "UART4 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on UART4_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on UART4. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).
+
 config UART4_RXDMA
 	bool "UART4 Rx DMA"
 	default n
@@ -1859,6 +1934,24 @@ config UART4_RXDMA
 	---help---
 		In high data rate usage, Rx DMA may eliminate Rx overrun errors
 
+config UART5_RS485
+	bool "RS-485 on UART5"
+	default n
+	depends on STM32_UART5
+	---help---
+		Enable RS-485 interface on UART5. Your board config will have to
+		provide GPIO_UART5_RS485_DIR pin definition. Currently it cannot be
+		used with UART5_RXDMA.
+
+config UART5_RS485_DIR_POLARITY
+	int "UART5 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on UART5_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on UART5. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).
+
 config UART5_RXDMA
 	bool "UART5 Rx DMA"
 	default n
@@ -1866,6 +1959,24 @@ config UART5_RXDMA
 	---help---
 		In high data rate usage, Rx DMA may eliminate Rx overrun errors
 
+config USART6_RS485
+	bool "RS-485 on USART6"
+	default n
+	depends on STM32_USART6
+	---help---
+		Enable RS-485 interface on USART6. Your board config will have to
+		provide GPIO_USART6_RS485_DIR pin definition. Currently it cannot be
+		used with USART6_RXDMA.
+
+config USART6_RS485_DIR_POLARITY
+	int "USART6 RS-485 DIR pin polarity"
+	default 1
+	range 0 1
+	depends on USART6_RS485
+	---help---
+		Polarity of DIR pin for RS-485 on USART6. Set to state on DIR pin which
+		enables TX (0 - low / nTXEN, 1 - high / TXEN).
+
 config USART6_RXDMA
 	bool "USART6 Rx DMA"
 	default n
@@ -1882,6 +1993,8 @@ config SERIAL_TERMIOS
 		If this is not defined, then the terminal settings (baud, parity, etc).
 		are not configurable at runtime; serial streams cannot be flushed, etc..
 
+endmenu
+
 menu "SPI Configuration"
 	depends on STM32_SPI
 
diff --git a/nuttx/arch/arm/src/stm32/stm32_lowputc.c b/nuttx/arch/arm/src/stm32/stm32_lowputc.c
index 7f7205672..6cb07dad9 100644
--- a/nuttx/arch/arm/src/stm32/stm32_lowputc.c
+++ b/nuttx/arch/arm/src/stm32/stm32_lowputc.c
@@ -67,6 +67,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_USART1_2STOP
 #  define STM32_CONSOLE_TX       GPIO_USART1_TX
 #  define STM32_CONSOLE_RX       GPIO_USART1_RX
+#  ifdef CONFIG_USART1_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_USART1_RS485_DIR
+#    if (CONFIG_USART1_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #elif defined(CONFIG_USART2_SERIAL_CONSOLE)
 #  define STM32_CONSOLE_BASE     STM32_USART2_BASE
 #  define STM32_APBCLOCK         STM32_PCLK1_FREQUENCY
@@ -76,6 +84,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_USART2_2STOP
 #  define STM32_CONSOLE_TX       GPIO_USART2_TX
 #  define STM32_CONSOLE_RX       GPIO_USART2_RX
+#  ifdef CONFIG_USART2_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_USART2_RS485_DIR
+#    if (CONFIG_USART2_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #elif defined(CONFIG_USART3_SERIAL_CONSOLE)
 #  define STM32_CONSOLE_BASE     STM32_USART3_BASE
 #  define STM32_APBCLOCK         STM32_PCLK1_FREQUENCY
@@ -85,6 +101,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_USART3_2STOP
 #  define STM32_CONSOLE_TX       GPIO_USART3_TX
 #  define STM32_CONSOLE_RX       GPIO_USART3_RX
+#  ifdef CONFIG_USART3_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_USART3_RS485_DIR
+#    if (CONFIG_USART3_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #elif defined(CONFIG_UART4_SERIAL_CONSOLE)
 #  define STM32_CONSOLE_BASE     STM32_UART4_BASE
 #  define STM32_APBCLOCK         STM32_PCLK1_FREQUENCY
@@ -94,6 +118,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_UART4_2STOP
 #  define STM32_CONSOLE_TX       GPIO_UART4_TX
 #  define STM32_CONSOLE_RX       GPIO_UART4_RX
+#  ifdef CONFIG_UART4_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_UART4_RS485_DIR
+#    if (CONFIG_UART4_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #elif defined(CONFIG_UART5_SERIAL_CONSOLE)
 #  define STM32_CONSOLE_BASE     STM32_UART5_BASE
 #  define STM32_APBCLOCK         STM32_PCLK1_FREQUENCY
@@ -103,6 +135,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_UART5_2STOP
 #  define STM32_CONSOLE_TX       GPIO_UART5_TX
 #  define STM32_CONSOLE_RX       GPIO_UART5_RX
+#  ifdef CONFIG_UART5_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_UART5_RS485_DIR
+#    if (CONFIG_UART5_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #elif defined(CONFIG_USART6_SERIAL_CONSOLE)
 #  define STM32_CONSOLE_BASE     STM32_USART6_BASE
 #  define STM32_APBCLOCK         STM32_PCLK2_FREQUENCY
@@ -112,6 +152,14 @@
 #  define STM32_CONSOLE_2STOP    CONFIG_USART6_2STOP
 #  define STM32_CONSOLE_TX       GPIO_USART6_TX
 #  define STM32_CONSOLE_RX       GPIO_USART6_RX
+#  ifdef CONFIG_USART6_RS485
+#    define STM32_CONSOLE_RS485_DIR GPIO_USART6_RS485_DIR
+#    if (CONFIG_USART6_RS485_DIR_POLARITY == 0)
+#      define STM32_CONSOLE_RS485_DIR_POLARITY false
+#    else
+#      define STM32_CONSOLE_RS485_DIR_POLARITY true
+#    endif
+#  endif
 #endif
 
 /* CR1 settings */
@@ -230,10 +278,19 @@ void up_lowputc(char ch)
   /* Wait until the TX data register is empty */
 
   while ((getreg32(STM32_CONSOLE_BASE + STM32_USART_SR_OFFSET) & USART_SR_TXE) == 0);
+#if STM32_CONSOLE_RS485_DIR
+  stm32_gpiowrite(STM32_CONSOLE_RS485_DIR, STM32_CONSOLE_RS485_DIR_POLARITY);
+#endif
 
   /* Then send the character */
 
   putreg32((uint32_t)ch, STM32_CONSOLE_BASE + STM32_USART_DR_OFFSET);
+
+#if STM32_CONSOLE_RS485_DIR
+  while ((getreg32(STM32_CONSOLE_BASE + STM32_USART_SR_OFFSET) & USART_SR_TC) == 0);
+  stm32_gpiowrite(STM32_CONSOLE_RS485_DIR, !STM32_CONSOLE_RS485_DIR_POLARITY);
+#endif
+
 #endif
 }
 
@@ -328,7 +385,14 @@ void stm32_lowsetup(void)
 
 #ifdef STM32_CONSOLE_TX
   stm32_configgpio(STM32_CONSOLE_TX);
-  stm32_configgpio(STM32_CONSOLE_TX);
+#endif
+#ifdef STM32_CONSOLE_RX
+  stm32_configgpio(STM32_CONSOLE_RX);
+#endif
+
+#if STM32_CONSOLE_RS485_DIR
+  stm32_configgpio(STM32_CONSOLE_RS485_DIR);
+  stm32_gpiowrite(STM32_CONSOLE_RS485_DIR, !STM32_CONSOLE_RS485_DIR_POLARITY);
 #endif
 
   /* Enable and configure the selected console device */
@@ -382,7 +446,14 @@ void stm32_lowsetup(void)
 
 #ifdef STM32_CONSOLE_TX
   stm32_configgpio(STM32_CONSOLE_TX);
-  stm32_configgpio(STM32_CONSOLE_TX);
+#endif
+#ifdef STM32_CONSOLE_RX
+  stm32_configgpio(STM32_CONSOLE_RX);
+#endif
+
+#if STM32_CONSOLE_RS485_DIR
+  stm32_configgpio(STM32_CONSOLE_RS485_DIR);
+  stm32_gpiowrite(STM32_CONSOLE_RS485_DIR, !STM32_CONSOLE_RS485_DIR_POLARITY);
 #endif
 
   /* Enable and configure the selected console device */
diff --git a/nuttx/arch/arm/src/stm32/stm32_serial.c b/nuttx/arch/arm/src/stm32/stm32_serial.c
index 45d685823..6c1861ef8 100644
--- a/nuttx/arch/arm/src/stm32/stm32_serial.c
+++ b/nuttx/arch/arm/src/stm32/stm32_serial.c
@@ -96,6 +96,19 @@
 #    endif
 #  endif
 
+/* Currently RS-485 support cannot be enabled when RXDMA is in use due to lack
+ * of testing - RS-485 support was developed on STM32F1x
+ */
+
+#  if (defined(CONFIG_USART1_RXDMA) && defined(CONFIG_USART1_RS485)) || \
+      (defined(CONFIG_USART2_RXDMA) && defined(CONFIG_USART2_RS485)) ||  \
+      (defined(CONFIG_USART3_RXDMA) && defined(CONFIG_USART3_RS485)) ||  \
+      (defined(CONFIG_UART4_RXDMA) && defined(CONFIG_UART4_RS485)) ||  \
+      (defined(CONFIG_UART5_RXDMA) && defined(CONFIG_UART5_RS485)) ||  \
+      (defined(CONFIG_USART6_RXDMA) && defined(CONFIG_USART6_RS485)) \
+#    error "RXDMA and RS-485 cannot be enabled at the same time for the same U[S]ART"
+#  endif
+
 /* For the F4, there are alternate DMA channels for USART1 and 6.
  * Logic in the board.h file make the DMA channel selection by defining
  * the following in the board.h file.
@@ -215,6 +228,11 @@ struct up_dev_s
   uint32_t          rxdmanext; /* Next byte in the DMA buffer to be read */
   char       *const rxfifo;    /* Receive DMA buffer */
 #endif
+
+#ifdef HAVE_RS485
+  const uint32_t    rs485_dir_gpio; /* U[S]ART RS-485 DIR GPIO pin configuration */
+  const bool        rs485_dir_polarity; /* U[S]ART RS-485 DIR pin state for TX enabled */
+#endif
 };
 
 /****************************************************************************
@@ -409,6 +427,15 @@ static struct up_dev_s g_usart1priv =
   .rxfifo        = g_usart1rxfifo,
 #endif
   .vector        = up_interrupt_usart1,
+
+#ifdef CONFIG_USART1_RS485
+  .rs485_dir_gpio = GPIO_USART1_RS485_DIR,
+#  if (CONFIG_USART1_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -460,6 +487,15 @@ static struct up_dev_s g_usart2priv =
   .rxfifo        = g_usart2rxfifo,
 #endif
   .vector        = up_interrupt_usart2,
+
+#ifdef CONFIG_USART2_RS485
+  .rs485_dir_gpio = GPIO_USART2_RS485_DIR,
+#  if (CONFIG_USART2_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -511,6 +547,15 @@ static struct up_dev_s g_usart3priv =
   .rxfifo        = g_usart3rxfifo,
 #endif
   .vector        = up_interrupt_usart3,
+
+#ifdef CONFIG_USART3_RS485
+  .rs485_dir_gpio = GPIO_USART3_RS485_DIR,
+#  if (CONFIG_USART3_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -562,6 +607,15 @@ static struct up_dev_s g_uart4priv =
   .rxfifo        = g_uart4rxfifo,
 #endif
   .vector        = up_interrupt_uart4,
+
+#ifdef CONFIG_UART4_RS485
+  .rs485_dir_gpio = GPIO_UART4_RS485_DIR,
+#  if (CONFIG_UART4_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -613,6 +667,15 @@ static struct up_dev_s g_uart5priv =
   .rxfifo        = g_uart5rxfifo,
 #endif
   .vector         = up_interrupt_uart5,
+
+#ifdef CONFIG_UART5_RS485
+  .rs485_dir_gpio = GPIO_UART5_RS485_DIR,
+#  if (CONFIG_UART5_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -664,6 +727,15 @@ static struct up_dev_s g_usart6priv =
   .rxfifo        = g_usart6rxfifo,
 #endif
   .vector         = up_interrupt_usart6,
+
+#ifdef CONFIG_USART6_RS485
+  .rs485_dir_gpio = GPIO_USART6_RS485_DIR,
+#  if (CONFIG_USART6_RS485_DIR_POLARITY == 0)
+  .rs485_dir_polarity = false,
+#  else
+  .rs485_dir_polarity = true,
+#  endif
+#endif
 };
 #endif
 
@@ -736,8 +808,8 @@ static void up_restoreusartint(struct up_dev_s *priv, uint16_t ie)
   /* And restore the interrupt state (see the interrupt enable/usage table above) */
 
   cr = up_serialin(priv, STM32_USART_CR1_OFFSET);
-  cr &= ~(USART_CR1_RXNEIE|USART_CR1_TXEIE|USART_CR1_PEIE);
-  cr |= (ie & (USART_CR1_RXNEIE|USART_CR1_TXEIE|USART_CR1_PEIE));
+  cr &= ~(USART_CR1_USED_INTS);
+  cr |= (ie & (USART_CR1_USED_INTS));
   up_serialout(priv, STM32_USART_CR1_OFFSET, cr);
 
   cr = up_serialin(priv, STM32_USART_CR3_OFFSET);
@@ -764,7 +836,7 @@ static inline void up_disableusartint(struct up_dev_s *priv, uint16_t *ie)
        * USART_CR1_IDLEIE    4  USART_SR_IDLE   Idle Line Detected             (not used)
        * USART_CR1_RXNEIE    5  USART_SR_RXNE   Received Data Ready to be Read
        * "              "       USART_SR_ORE    Overrun Error Detected
-       * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete          (not used)
+       * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete          (used only for RS-485)
        * USART_CR1_TXEIE     7  USART_SR_TXE    Transmit Data Register Empty
        * USART_CR1_PEIE      8  USART_SR_PE     Parity Error
        *
@@ -783,7 +855,7 @@ static inline void up_disableusartint(struct up_dev_s *priv, uint16_t *ie)
        * overlap.  This logic would fail if we needed the break interrupt!
        */
 
-      *ie = (cr1 & (USART_CR1_RXNEIE|USART_CR1_TXEIE|USART_CR1_PEIE)) | (cr3 & USART_CR3_EIE);
+      *ie = (cr1 & (USART_CR1_USED_INTS)) | (cr3 & USART_CR3_EIE);
     }
 
   /* Disable all interrupts */
@@ -893,6 +965,14 @@ static int up_setup(struct uart_dev_s *dev)
       stm32_configgpio(priv->rts_gpio);
     }
 
+#if HAVE_RS485
+  if (priv->rs485_dir_gpio != 0)
+    {
+      stm32_configgpio(priv->rs485_dir_gpio);
+      stm32_gpiowrite(priv->rs485_dir_gpio, !priv->rs485_dir_polarity);
+    }
+#endif
+
   /* Configure CR2 */
   /* Clear STOP, CLKEN, CPOL, CPHA, LBCL, and interrupt enable bits */
 
@@ -1174,7 +1254,7 @@ static int up_interrupt_common(struct up_dev_s *priv)
        * USART_CR1_IDLEIE    4  USART_SR_IDLE   Idle Line Detected              (not used)
        * USART_CR1_RXNEIE    5  USART_SR_RXNE   Received Data Ready to be Read
        * "              "       USART_SR_ORE    Overrun Error Detected
-       * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete           (not used)
+       * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete           (used only for RS-485)
        * USART_CR1_TXEIE     7  USART_SR_TXE    Transmit Data Register Empty
        * USART_CR1_PEIE      8  USART_SR_PE     Parity Error
        *
@@ -1189,6 +1269,21 @@ static int up_interrupt_common(struct up_dev_s *priv)
        * being used.
        */
 
+#ifdef HAVE_RS485
+      /* Transmission of whole buffer is over - TC is set, TXEIE is cleared.
+       * Note - this should be first, to have the most recent TC bit value from
+       * SR register - sending data affects TC, but without refresh we will not
+       * know that...
+       */
+
+      if ((priv->sr & USART_SR_TC) != 0 && (priv->ie & USART_CR1_TCIE) != 0 &&
+          (priv->ie & USART_CR1_TXEIE) == 0)
+        {
+          stm32_gpiowrite(priv->rs485_dir_gpio, !priv->rs485_dir_polarity);
+          up_restoreusartint(priv, priv->ie & ~USART_CR1_TCIE);
+        }
+#endif
+
       /* Handle incoming, receive bytes. */
 
       if ((priv->sr & USART_SR_RXNE) != 0 && (priv->ie & USART_CR1_RXNEIE) != 0)
@@ -1222,13 +1317,14 @@ static int up_interrupt_common(struct up_dev_s *priv)
 
       if ((priv->sr & USART_SR_TXE) != 0 && (priv->ie & USART_CR1_TXEIE) != 0)
         {
-           /* Transmit data regiser empty ... process outgoing bytes */
+           /* Transmit data register empty ... process outgoing bytes */
 
            uart_xmitchars(&priv->dev);
            handled = true;
         }
     }
-    return OK;
+
+  return OK;
 }
 
 /****************************************************************************
@@ -1527,6 +1623,10 @@ static bool up_dma_rxavailable(struct uart_dev_s *dev)
 static void up_send(struct uart_dev_s *dev, int ch)
 {
   struct up_dev_s *priv = (struct up_dev_s*)dev->priv;
+#ifdef HAVE_RS485
+  if (priv->rs485_dir_gpio != 0)
+    stm32_gpiowrite(priv->rs485_dir_gpio, priv->rs485_dir_polarity);
+#endif
   up_serialout(priv, STM32_USART_DR_OFFSET, (uint32_t)ch);
 }
 
@@ -1547,7 +1647,7 @@ static void up_txint(struct uart_dev_s *dev, bool enable)
    *
    * Enable             Bit Status          Meaning                      Usage
    * ------------------ --- --------------- ---------------------------- ----------
-   * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete        (not used)
+   * USART_CR1_TCIE      6  USART_SR_TC     Transmission Complete        (used only for RS-485)
    * USART_CR1_TXEIE     7  USART_SR_TXE    Transmit Data Register Empty
    * USART_CR3_CTSIE    10  USART_SR_CTS    CTS flag                     (not used)
    */
@@ -1558,7 +1658,20 @@ static void up_txint(struct uart_dev_s *dev, bool enable)
       /* Set to receive an interrupt when the TX data register is empty */
 
 #ifndef CONFIG_SUPPRESS_SERIAL_INTS
-      up_restoreusartint(priv, priv->ie | USART_CR1_TXEIE);
+      uint16_t ie = priv->ie | USART_CR1_TXEIE;
+
+      /* If RS-485 is supported on this U[S]ART, then also enable the
+       * transmission complete interrupt.
+       */
+
+#  ifdef HAVE_RS485
+      if (priv->rs485_dir_gpio != 0)
+        {
+          ie |= USART_CR1_TCIE;
+        }
+#  endif
+
+      up_restoreusartint(priv, ie);
 
       /* Fake a TX interrupt here by just calling uart_xmitchars() with
        * interrupts disabled (note this may recurse).
@@ -1573,6 +1686,7 @@ static void up_txint(struct uart_dev_s *dev, bool enable)
 
       up_restoreusartint(priv, priv->ie & ~USART_CR1_TXEIE);
     }
+
   irqrestore(flags);
 }
 
diff --git a/nuttx/arch/arm/src/stm32/stm32_uart.h b/nuttx/arch/arm/src/stm32/stm32_uart.h
index a70923cbf..8ff6a9975 100644
--- a/nuttx/arch/arm/src/stm32/stm32_uart.h
+++ b/nuttx/arch/arm/src/stm32/stm32_uart.h
@@ -223,6 +223,20 @@
 #  undef SERIAL_HAVE_ONLY_DMA
 #endif
 
+/* Is RS-485 used? */
+
+#if defined(CONFIG_USART1_RS485) || defined(CONFIG_USART2_RS485) || \
+    defined(CONFIG_USART3_RS485) || defined(CONFIG_UART4_RS485)  || \
+    defined(CONFIG_UART5_RS485) || defined(CONFIG_USART6_RS485)
+#  define HAVE_RS485 1
+#endif
+
+#ifdef HAVE_RS485
+#  define USART_CR1_USED_INTS    (USART_CR1_RXNEIE | USART_CR1_TXEIE | USART_CR1_PEIE | USART_CR1_TCIE)
+#else
+#  define USART_CR1_USED_INTS    (USART_CR1_RXNEIE | USART_CR1_TXEIE | USART_CR1_PEIE)
+#endif
+
 /************************************************************************************
  * Public Types
  ************************************************************************************/
diff --git a/nuttx/configs/shenzhou/src/up_mmcsd.c b/nuttx/configs/shenzhou/src/up_mmcsd.c
index 531fbfd7e..adf695cd5 100644
--- a/nuttx/configs/shenzhou/src/up_mmcsd.c
+++ b/nuttx/configs/shenzhou/src/up_mmcsd.c
@@ -65,6 +65,12 @@
 #  endif
 #endif
 
+/* Can't support MMC/SD features if MMC/SD driver support is not selected */
+
+#ifndef CONFIG_MMCSD
+#  undef HAVE_MMCSD
+#endif
+
 /* Can't support MMC/SD features if mountpoints are disabled */
 
 #ifdef CONFIG_DISABLE_MOUNTPOINT