arch/arm/src/stm32: Add internal pull-up option for SDIO pins (also picks up an unrelated change to a README.txt file)

README.txt

@@ -68,6 +68,10 @@ ENVIRONMENTS
       the time as Cygwin, perhaps 20 minutes for the basic Ubuntu install
       (vs. more than a day for the complete Cygwin install).
 
+      There have been even more recent ports of Linux environment to
+      Windows.  I need to update this section to include some mention of
+      these alternatives.
+
     - The MSYS environment.  I have no experience using the MSYS environment
       and that configuration will not be discussed in this README file.
       See http://www.mingw.org/wiki/MSYS if you are interested in
@@ -76,6 +80,17 @@ ENVIRONMENTS
       is that it is closer to a native Windows environment and uses only a
       minimal of add-on POSIX-land tools.
 
+    - Other POSIX environments.  Check out:
+
+        UnxUtils: https://sourceforge.net/projects/unxutils/,
+          https://en.wikipedia.org/wiki/UnxUtils
+        MobaXterm: https://mobaxterm.mobatek.net/
+        Gow`: https://github.com/bmatzelle/gow/wiki
+
+      Disclaimer:  In priniple, these should work.  However, I have never
+      used any of these environments and cannot guarantee that there is
+      not some less-than-obvious issues.
+
   NuttX can also be installed and built on a native Windows system, but with
   some potential tool-related issues (see the discussion "Native Windows
   Build" under "Building NuttX" below).  GNUWin32 is used to provide

arch/arm/src/stm32/Kconfig

@@ -7602,6 +7602,15 @@ config STM32_SDIO_CARD
 		Build in additional support needed only for SDIO cards (vs. SD
 		memory cards)
 
+config STM32_SDIO_PULLUP
+	bool "Enable internal Pull-Ups"
+	default n
+	---help---
+		If you are using an external SDCard module that does not have the
+		pull-up resistors for the SDIO interface (like the Gadgeteer SD Card
+		Module) then enable this option to activate the internal pull-up
+		resistors.
+
 config STM32_SDIO_DMA
 	bool "Support DMA data transfers"
 	default y if STM32_DMA2

arch/arm/src/stm32/stm32_sdio.c

@@ -151,6 +151,14 @@
 #  undef CONFIG_SDIO_XFRDEBUG
 #endif
 
+/* Enable the SDIO pull-up resistors if needed */
+
+#ifdef CONFIG_STM32_SDIO_PULLUP
+#  define SDIO_PULLUP_ENABLE GPIO_PULLUP
+#else
+#  define SDIO_PULLUP_ENABLE 0
+#endif
+
 /* Friendly CLKCR bit re-definitions ****************************************/
 
 #define SDIO_CLKCR_RISINGEDGE    (0)
@@ -3038,14 +3046,14 @@ FAR struct sdio_dev_s *sdio_initialize(int slotno)
    */
 
 #ifndef CONFIG_SDIO_MUXBUS
-  stm32_configgpio(GPIO_SDIO_D0);
+  stm32_configgpio(GPIO_SDIO_D0 | SDIO_PULLUP_ENABLE);
 #ifndef CONFIG_STM32_SDIO_WIDTH_D1_ONLY
-  stm32_configgpio(GPIO_SDIO_D1);
+  stm32_configgpio(GPIO_SDIO_D1 | SDIO_PULLUP_ENABLE);
-  stm32_configgpio(GPIO_SDIO_D2);
+  stm32_configgpio(GPIO_SDIO_D2 | SDIO_PULLUP_ENABLE);
-  stm32_configgpio(GPIO_SDIO_D3);
+  stm32_configgpio(GPIO_SDIO_D3 | SDIO_PULLUP_ENABLE);
 #endif
-  stm32_configgpio(GPIO_SDIO_CK);
+  stm32_configgpio(GPIO_SDIO_CK | SDIO_PULLUP_ENABLE);
-  stm32_configgpio(GPIO_SDIO_CMD);
+  stm32_configgpio(GPIO_SDIO_CMD | SDIO_PULLUP_ENABLE);
 #endif
 
   /* Reset the card and assure that it is in the initial, unconfigured