diff --git a/ports/ARMCM3-STM32F103/pal_lld.h b/ports/ARMCM3-STM32F103/pal_lld.h
index 7c1bb4399..33e6f959a 100644
--- a/ports/ARMCM3-STM32F103/pal_lld.h
+++ b/ports/ARMCM3-STM32F103/pal_lld.h
@@ -198,8 +198,8 @@ typedef GPIO_TypeDef * ioportid_t;
  *       code.
  */
 #define pal_lld_writegroup(port, mask, offset, bits) {                  \
-  (bus)->bus_portid->BSRR = ((~(bits) & (mask)) << (16 + (offset))) |   \
-                            ((bits) & (mask)) << (offset);              \
+  (port)->BSRR = ((~(bits) & (mask)) << (16 + (offset))) |              \
+                 (((bits) & (mask)) << (offset));                       \
 }
 
 /**
@@ -207,15 +207,12 @@ typedef GPIO_TypeDef * ioportid_t;
  *
  * @param[in] port the port identifier
  * @param[in] pad the pad number within the port
- * @param[out] value the logical value, the value must be @p 0 or @p 1
+ * @param[out] bit the logical value, the value must be @p 0 or @p 1
  *
  * @note This function is not meant to be invoked directly by the application
  *       code.
  */
-#define pal_lld_writepad(port, pad, value) {                            \
-  (bus)->bus_portid->BSRR = (((~(value) & 1) << ((pad) + 16)) |         \
-                            ((((value) & 1) << (pad)));                 \
-}
+#define pal_lld_writepad(port, pad, bit) pal_lld_writegroup(port, 1, pad, bit)
 
 /**
  * @brief GPIO port setup.
diff --git a/src/lib/pal.h b/src/lib/pal.h
index 11137c6cb..cac306c43 100644
--- a/src/lib/pal.h
+++ b/src/lib/pal.h
@@ -31,6 +31,16 @@
 #include "pal_lld.h"
 #endif
 
+/**
+ * @brief Logical low state.
+ */
+#define PAL_LOW 0
+
+/**
+ * @brief Logical high state.
+ */
+#define PAL_HIGH 1
+
 /**
  * @brief Port bit helper macro.
  * @details This macro calculates the mask of a bit within a port.
@@ -241,7 +251,7 @@ typedef struct {
  *
  * @param[in] port the port identifier
  * @param[in] pad the pad number within the port
- * @param[out] value the logical value, the value must be @p 0 or @p 1
+ * @param[out] bit the logical value, the value must be @p 0 or @p 1
  *
  * @note The operation is not guaranteed to be atomic on all the architectures,
  *       for atomicity and/or portability reasons you may need to enclose port
@@ -253,12 +263,12 @@ typedef struct {
  *       @p palWritePort().
  */
 #if !defined(pal_lld_writepad) || defined(__DOXYGEN__)
-#define palWritePad(port, pad, value) {                                 \
+#define palWritePad(port, pad, bit) {                                   \
   palWritePort(port, (palReadLatch(port) & ~PAL_PORT_BIT(pad)) |        \
-                     (((value) & 1) << pad));                           \
+                     (((bit) & 1) << pad));                             \
 }
 #else
-#define palWritePad(port, pad, value) pal_lld_writepad(port, pad, value)
+#define palWritePad(port, pad, bit) pal_lld_writepad(port, pad, bit)
 #endif
 
 /**