AMDL: Add support to Peripheral as Output with Read back. From Alan Carvalho de Assis.

arch/arm/src/samdl/sam_port.c

@@ -310,11 +310,26 @@ static inline void sam_configperiph(uintptr_t base, port_pinset_t pinset)
   pin = (pinset & PORT_PIN_MASK) >> PORT_PIN_SHIFT;
   bit = (1 << pin);
 
+  /* If pin is output with readback then set the pin as output */
+
+  if ((pinset & PORT_OUTREADBACK_MASK) == PORT_OUTREADBACK_ENABLE)
+    {
+      putreg32(bit, base + SAM_PORT_DIRSET_OFFSET);
+    }
+
   /* Set the pin configuration.  This will be an peripheral with the
    * selected function.
    */
 
   regval = (PORT_WRCONFIG_WRPINCFG | PORT_WRCONFIG_WRPMUX | PORT_WRCONFIG_PMUXEN);
+
+  /* If pin is output with readback then enable the input buffer */
+
+  if ((pinset & PORT_OUTREADBACK_MASK) == PORT_OUTREADBACK_ENABLE)
+    {
+      regval |= PORT_WRCONFIG_INEN;
+    }
+
   if (pin > 16)
     {
        /* Select the upper half word and adjust the bit setting */

arch/arm/src/samdl/sam_port.h

@@ -76,9 +76,9 @@
  *   ------------ -----------------------------
  *   PORT Input:  MMRR .... .S.. .... ..PB BBBB
  *   PORT Output: MM.. .... D..V .... ..PB BBBB
- *   Peripheral:  MM.. FFF. .... II.. ..PB BBBB
+ *   Peripheral:  MM.. FFFO .... II.. ..PB BBBB
  *   ------------ -----------------------------
- *                MMRR FFF. DS.V II.. ..PB BBBB
+ *                MMRR FFFO DS.V II.. ..PB BBBB
  */
 
 /* Input/output/peripheral mode:
@@ -162,6 +162,23 @@
 #define PORT_FUNCG                 (PORT_PERIPHERAL | _PORT_FUNCG) /* Function G */
 #define PORT_FUNCH                 (PORT_PERIPHERAL | _PORT_FUNCH) /* Function H */
 
+/* Output and Input Buffer both enabled to let readback
+ *
+ *   MODE         BITFIELDS
+ *   ------------ -----------------------------
+ *                2222 1111 1111 1100 0000 0000
+ *                3210 9876 5432 1098 7654 3210
+ *   ------------ -----------------------------
+ *   PORT Input:  .... .... .... .... .... ....
+ *   PORT Output: .... .... .... .... .... ....
+ *   Peripheral:  .... ...O .... .... .... ....
+ */
+
+#define PORT_OUTREADBACK_SHIFT     (16)       /* Bit 16: Pin output and input buffer enabled */
+#define PORT_OUTREADBACK_MASK      (1 << PORT_OUTREADBACK_SHIFT)
+#  define PORT_OUTREADBACK_DISABLE (0 << PORT_OUTREADBACK_SHIFT)
+#  define PORT_OUTREADBACK_ENABLE  (1 << PORT_OUTREADBACK_SHIFT)
+
 /* Output drive control
  *
  *   MODE         BITFIELDS