Make both examples do the same thing in the same lines

New objective:
 - Toggle D1 with 2 Hz
 - Turn off D2 if USR_SW1 is pressed
 
Also, refine comments and explain the timing better.

example_standalone_driverlib/main.c

 /*
+ * Toggles LED on pin 1 on port N
+ * Turns off LED on pin 0 on port N if button (USR_SW1 on port J pin 0) is pressed
  *
- * Toggles led on pin 1 on port N
- *
- * Already set build options (no need to change anything):
+ * Already set build options of this project (no need to change anything):
  * Stack size set to 1024 byte
- * Heap size disabled - No malloc()
- * No code optimization
- * Strict floating point interrupt behaviour
+ * Heap size disabled - No malloc() available
+ * No code optimization - Easier debugging
+ * Strict floating point interrupt behavior
  * Hardware floating point unit activated
- *
  */
 
-#define TARGET_IS_TM4C129_RA2
-#include <stdbool.h> /*driverlib header requires stdbool.h to be included a first header file before any driverlib header*/
-#include <stdint.h>
-#include <driverlib/gpio.h>
-#include <driverlib/pin_map.h>/*supplies GPIO_PIN_x*/
-#include <driverlib/sysctl.h>
-#include <driverlib/rom.h>
-#include <inc/hw_memmap.h>/*supplies GPIO_PORTx_BASE*/
+#define TARGET_IS_TM4C129_RA2 /* Tells rom.h the version of the silicon */
+#include <stdint.h> /* C99 header for uint*_t types */
+#include <stdbool.h> /* Driverlib headers require stdbool.h to be included first */
+#include <driverlib/gpio.h> /* Supplies GPIO* functions and GPIO_PIN_x */
+#include <driverlib/sysctl.h> /* Supplies SysCtl* functions and SYSCTL_* macros */
+#include <driverlib/rom.h> /* Supplies ROM_* variations of functions */
+#include <inc/hw_memmap.h> /* Supplies GPIO_PORTx_BASE */
 
-/*Controller is initially clocked with 16MHz*/
-/* !! Changing this define does not change clock speed !! */
-#define F_CPU 16000000
-
-void main (void) {
+/* Controller is initially clocked with 16 MHz (via PIOSC) */
+/* !!! Changing this macro does not change clock speed !!! */
+#define F_CPU (16000000)
 
+int main (void)
+{
     uint32_t ui32Strength;
     uint32_t ui32PinType;
-    uint8_t ui8val = 1;
-    uint32_t ui32Loop = 0;
+    uint8_t ui8button;
+    uint8_t ui8toggle = (1<<1);
 
-	/*activate gpio port n*/
+    /* Activate GPIO ports */
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOJ);
     SysCtlPeripheralEnable(SYSCTL_PERIPH_GPION);
 
+    /* Set pin 0 of GPIO port J to digital input */
+    GPIOPinTypeGPIOInput(GPIO_PORTJ_BASE, GPIO_PIN_0);
+
+
+    /* Enable pull-up for button on pin 0 of port J
+     * Note the API difference between the *Get and *Set functions. */
+    GPIOPadConfigGet(GPIO_PORTJ_BASE, 0, &ui32Strength, &ui32PinType);
+    GPIOPadConfigSet(GPIO_PORTJ_BASE, GPIO_PIN_0, ui32Strength, GPIO_PIN_TYPE_STD_WPU);
+
+    /* Set pins 0 & 1 of GPIO port N to digital output */
+    GPIOPinTypeGPIOOutput(GPIO_PORTN_BASE, GPIO_PIN_1 | GPIO_PIN_0);
+
+
+    while(1) {
+        /* Toggle bit 1 in variable ui8toggle */
+        ui8toggle = ui8toggle ^ (1<<1);
+        /* Write value of ui8toggle to pin 1 of port N */
+        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_1, ui8toggle);
 
-    /*set pin 1 of gpio port n to output*/
-    GPIOPinTypeGPIOOutput(GPIO_PORTN_BASE,GPIO_PIN_1);
+        /* Read value of pin 0 on port j into variable */
+        ui8button = GPIOPinRead(GPIO_PORTJ_BASE, GPIO_PIN_0);
+        /* Set pin 0 of port N accordingly */
+        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, ui8button);
 
-    /*configure GPIO_PIN_1 on port N as std pin*/
-    GPIOPadConfigGet(GPIO_PORTN_BASE, 1/*api requires pin number [0-7] instead of bit packed representation (e.g., GPIO_PIN_1 )*/, &ui32Strength, &ui32PinType);
-    GPIOPadConfigSet(GPIO_PORTN_BASE, GPIO_PIN_1,ui32Strength,GPIO_PIN_TYPE_STD);
+        /* Delay for *approximately* 0.5 s.
+         * 16M CPU cycles per second / 2 / 3 (SysCtlDelay factor) = 2666667
+         * The actual delay can be longer due to interrupts! This is not suitable for exact timing. */
+        ROM_SysCtlDelay(F_CPU/2/3);
 
-    for(;;) {
-        ui8val = ui8val ^ 2;/*toggle bit 1 in variable val*/
-        /*write value of val to pin 1 of port n*/
-        GPIOPinWrite (GPIO_PORTN_BASE, GPIO_PIN_1, ui8val);
-        // for(ui32Loop = 0; ui32Loop < 400000; ui32Loop++){}
-        ROM_SysCtlDelay(F_CPU/2/3);  //approx 0,5 s
     }
 }

example_standalone_register/main.c

 /*
+ * Toggles LED on pin 1 on port N
+ * Turns off LED on pin 0 on port N if button (USR_SW1 on port J pin 0) is pressed
  *
- * Toggles led on pin 1 on port N
- *
- * Already set build options (no need to change anything):
+ * Already set build options of this project (no need to change anything):
  * Stack size set to 256 byte
- * Heap size disabled - No malloc()
- * No code optimization
- * Strict floating point interrupt behaviour
+ * Heap size disabled - No malloc() available
+ * No code optimization - Easier debugging
+ * Strict floating point interrupt behavior
  * Hardware floating point unit activated
- *
  */
 
-#include <stdint.h>
-#include <inc/tm4c1294ncpdt.h>
 
-int main(void)
+#include <stdint.h> /* C99 header for uint*_t types */
+#include <stdbool.h> /* Driverlib headers require stdbool.h to be included first */
+#include <inc/tm4c1294ncpdt.h> /* Supplies SYSCTL_RCGCGPIO*, GPIO_PORT* macros */
+#include <inc/hw_types.h> /* Supplies HWREG macro */
+
+
+
+/* Controller is initially clocked with 16 MHz (via PIOSC) */
+/* !!! Changing this macro does not change clock speed !!! */
+#define F_CPU (16000000)
+
+int main (void)
 {
+
     uint32_t ui32Loop;
+    uint8_t ui8button;
+    uint8_t ui8toggle = (1<<1);
+
+    /* Activate GPIO ports */
+    SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R12 | SYSCTL_RCGCGPIO_R8;
+
+
+    /* Set pin 0 of GPIO port J to digital input */
+    GPIO_PORTJ_AHB_DEN_R |=  (1<<0);
+    GPIO_PORTJ_AHB_DIR_R &= ~(1<<0);
 
-    // Enable the GPIO port that is used for the on-board LED.
-    SYSCTL_RCGCGPIO_R = SYSCTL_RCGCGPIO_R12|SYSCTL_RCGCGPIO_R8;
+    /* Enable pull-up for button on pin 0 of port J */
+    GPIO_PORTJ_AHB_PUR_R |= (1<<0);
 
-    // Enable the GPIO pin for the LED (PN0).  Set the direction as output, and
-    // Enable the GPIO pin for digital function.
-    GPIO_PORTN_DIR_R = 0x01;
-    GPIO_PORTN_DEN_R = 0x01;
-    //Digital Enable for PortJ USR Switch1
-    GPIO_PORTJ_AHB_DEN_R = 0x01;
 
-    //Enable Pull Up for PortJ USR Switch1
-    GPIO_PORTJ_AHB_PUR_R = 0x01;
 
-    // Loop forever.
-    //
-    while(1)
-       {
-           //
-           // Toggle LED if USR1 is Pressed.
-           //
-           GPIO_PORTN_DATA_R ^= ~(GPIO_PORTJ_AHB_DATA_R) & 0x01;
+    /* Set pins 0 & 1 of GPIO port N to digital output */
+    GPIO_PORTN_DEN_R |= (1<<1) | (1<<0);
+    GPIO_PORTN_DIR_R |= (1<<1) | (1<<0);
 
-           //
-           // Delay for a bit.
-           //
-           for(ui32Loop = 0; ui32Loop < 400000; ui32Loop++);
+    while(1) {
+        /* Toggle bit 1 in variable ui8toggle */
+        ui8toggle = ui8toggle ^ (1<<1);
+        /* Write value of ui8toggle to pin 1 of port N */
+        HWREG(GPIO_PORTN_DATA_BITS_R + (1<<1)) = ui8toggle;
 
-       }
+        /* Read value of pin 0 on port j into variable */
+        ui8button = HWREG(GPIO_PORTJ_AHB_DATA_BITS_R + (1<<0));
+        /* Set pin 0 of port N accordingly */
+        HWREG(GPIO_PORTN_DATA_BITS_R + (1<<0)) = ui8button;
 
+        /* Delay for *approximately* 0.5 s by counting to 615385:
+         * 615385 = 16M cycles per second / 2 / approximately(!) 13 CPU cycles per loop iteration on average.
+         * The CPU cycles per iteration vary widely, e.g., due to compiler and hardware optimizations! */
+        for(ui32Loop = 0; ui32Loop < 615385; ui32Loop++)
+            __nop(); /* "No operation", prohibits possible loop elimination by the compiler. */
+    }
 }