perf(Examples,PeriphDrivers): Reset USB block when operating in low p…

…ower modes for MAX32650 (#728)

Examples/MAX32650/LP/main.c

@@ -213,6 +213,9 @@ int main(void)
 
     MXC_LP_EnableSRAM0(); // Global variables are in RAM0
 
+    // Resets the USB block to its initial state - where the operating current is at its minimum.
+    MXC_LP_USBClearPONRST();
+
     PRINT("All unused RAMs shutdown.\n");
     setTrigger(1);
 

Libraries/PeriphDrivers/Include/MAX32650/lp.h

@@ -381,6 +381,19 @@ void MXC_LP_EnterDeepSleepMode(void);
  */
 void MXC_LP_EnterBackupMode(void);
 
+/**
+ * @brief      Places the USB block into its initial state where the operating current is at its minimum.
+ *             This function must be called when the USB block is not used in order to achieve low power 
+ *             current readings.
+ */
+void MXC_LP_USBClearPONRST(void);
+
+/**
+ * @brief      Enables the USB (clock generator) if the USB PONRST (0x410) register was previously cleared
+ *             to put the device into a low power mode.
+ */
+void MXC_LP_USBSetPONRST(void);
+
 /**@} end of group lp */
 
 #ifdef __cplusplus

Libraries/PeriphDrivers/Source/LP/lp_me10.c

@@ -36,6 +36,7 @@
 #include "pwrseq_regs.h"
 #include "mxc_errors.h"
 #include "gcr_regs.h"
+#include "usbhs_regs.h"
 #include "mxc_sys.h"
 
 /* **** Variable Declaration **** */
@@ -711,3 +712,21 @@ void MXC_LP_EnterBackupMode(void)
     MXC_GCR->pmr |= MXC_S_GCR_PMR_MODE_BACKUP;
     while (1) {}
 }
+
+/* ************************************************************************** */
+void MXC_LP_USBClearPONRST(void)
+{
+    // This register is used during the power-on stage or used as a global reset
+    // for the USB block. For this case, the PONRST is used as a global reset
+    // and setting this register to 0 will force the USB block to its initial
+    // state - where the operating current is at its minimum.
+    MXC_USBHS->m31_phy_ponrst = 0;
+}
+
+/* ************************************************************************** */
+void MXC_LP_USBSetPONRST(void)
+{
+    // Re-enables the clock generator and the USB block if PONRST was used as
+    // a global reset for operating in low power modes.
+    MXC_USBHS->m31_phy_ponrst = 1;
+}