Add memory map io

Author: theEmbeddedGeorge

Data_Struct_Implementation/memoryMap/GPIO_memory_map.png

@@ -0,0 +1,75 @@
+## Memory map IO register Implementation
+
+### **Problem statement**
+
+*Suppose we have a GPIO memory map as follow, please implement a data struture that enables setting/clear certain register in the map in a clean and easy-to-understand manner. This is a **little endian** machine.*
+
+![GPIO Memory Map](GPIO_memory_map.png)
+
+```Please set 1 to GPIO 15.```
+
+*(GPIO<pin_num> are set by writting 1 to the bit<pin_num> of ODR register)*.
+
+### **Implementation**
+
+```c
+// Volatile for register values. Hardware may change its value at any time
+typedef struct {
+    voltatile uint32_t MODER,  // little endian, LSB at lowest address
+    voltatile uint32_t OTYPER,
+    voltatile uint32_t OSPEEDR,
+    voltatile uint32_t PUPDR,
+    voltatile uint32_t IDR,
+    voltatile uint32_t ODR,
+    voltatile uint32_t BSRR,
+    voltatile uint32_t LCKR,
+    voltatile uint32_t AFR[2],
+    voltatile uint32_t BRR,
+    voltatile uint32_t ASCR,  
+} GPIO_REG;
+
+// Register port map
+#define GPIO_A = ((GPIO_REG*) 0x48000000)
+#define GPIO_B = ((GPIO_REG*) 0x48000400)
+#define GPIO_C = ((GPIO_REG*) 0x48000800)
+
+// Set pin 15 of GPIOA to 1
+GPIO_A->ODR |= 1UL << 15;
+
+// Macro to set arbitrary GPIO pin of any port 
+#define SET_GPIO(pin_num, GPIO_PORT) (GPIO_PORT->ODR = 1UL<<pin_num;)
+
+```
+
+### **Follow up question**
+
+*What if in the original memory map, the following registers are 16-bit register instead of 32-bit? How will you change the data structure?*
+
+```
+uint16_t OTYPER
+uint16_t IDR
+uint16_t ODR
+```
+
+### **Implementation**
+
+```c
+#define voltatile _IO
+
+typedef struct {
+    _IO uint32_t MODER,
+    _IO uint16_t OTYPER,
+        uint16_t rev0,  // 2 byte padding
+    _IO uint32_t OSPEEDR,
+    _IO uint32_t PUPDR,
+    _IO uint16_t IDR,
+        uint16_t rev1,  // 2 byte padding
+    _IO uint16_t ODR,
+        uint16_t rev2,  // 2 byte padding
+    _IO uint32_t BSRR,
+    _IO uint32_t LCKR,
+    _IO uint32_t AFR[2],
+    _IO uint32_t BRR,
+    _IO uint32_t ASCR,  
+} GPIO_REG;
+```

Data_Struct_Implementation/memoryMap/memory_map_io.md

@@ -1,6 +1,6 @@
 ## Apple On-site interview process
 
-```45 minutes per round```
+```Disclaimer: all information are from public online resources!```
 
 ### 1st round
 - Hiring Manager round

Interview/Company/apple.md

@@ -1,5 +1,7 @@
 ### Lyft Level 5 questions
 
+```Disclaimer: all information are from public online resources!```
+
 ### Phone screen
 
 **Question: Interrupts are an important part of embedded systems. Consequently, many compiler vendors offer an extension to standard C to support interrupts. Typically, this new key word is __interrupt. The following code uses __interrupt to define an interrupt service routine. Comment on the code.**

Interview/Company/lyft.md

@@ -49,30 +49,39 @@
 5. Assembly
 
 ### C. Data Structures & Implementation
-1. [Ring Buffer](./Data_Struct_Implementation/circularRingBuffer/README.md)
-2. [Hash Table](./Data_Struct_Implementation/hashTable/README.md)
-3. [Heap (priority queue)](./Data_Struct_Implementation/binaryHeap/README.md)
-4. [Stack](./Data_Struct_Implementation/stack/README.md)
-5. [Queue](./Data_Struct_Implementation/queue/README.md)
-6. [Binary Search Tree](Data_Struct_Implementation/BST/README.md)
-7. Red Black Tree
-8. Minium Spanning Tree (MST)
-9. [Finite State Machine](Data_Struct_Implementation/stateMachine/README.md)
-10. Simple Task Scheduler
-11. [Endianess Check](Data_Struct_Implementation/endianess/README.md)
-12. [Swap Endianess](Data_Struct_Implementation/endianessSwap/README.md)
-13. Signness Check
-14. [Array of Bits](Data_Struct_Implementation/bitsArray/README.md)
-15. Low Pass Filter
-16. Common STL function implementation
+1. [Finite State Machine](Data_Struct_Implementation/stateMachine/README.md)
+2. Simple Task Scheduler
+3. [Endianess Check](Data_Struct_Implementation/endianess/README.md)
+4. [Swap Endianess](Data_Struct_Implementation/endianessSwap/README.md)
+5. Signness Check
+6. [Array of Bits](Data_Struct_Implementation/bitsArray/README.md)
+7. Low Pass Filter
+8. [Memory map IO register manipulation](Data_Struct_Implementation/memoryMap/memory_map_io.md)
+9. Data Structure
+    1.  [Ring Buffer](./Data_Struct_Implementation/circularRingBuffer/README.md)
+    2.  [Hash Table](./Data_Struct_Implementation/hashTable/README.md)
+    3.  [Heap (priority queue)](./Data_Struct_Implementation/binaryHeap/README.md)
+    4.  [Stack](./Data_Struct_Implementation/stack/README.md)
+    5.  [Queue](./Data_Struct_Implementation/queue/README.md)
+    6.  [Binary Search Tree](Data_Struct_Implementation/BST/README.md)
+    7.  Red Black Tree
+    8.  Minium Spanning Tree (MST)
+10. Math
+    1.  Rolling average
+    2.  Taylor Series
+    3.  Dividing by a constant
+    4.  Sine Functions with Lookup table
+    5.  Linear Interpolation
+    6.  Floating Point Arthimetic
+11. Common STL function implementation
     1. [Safe memcpy (memmove)](Data_Struct_Implementation/memcpy_memmove/README.md)
     2. [itoa](Data_Struct_Implementation/itoa/README.md)
     3. [atoi](Data_Struct_Implementation/atoi/README.md)
     4. [sizeof](Data_Struct_Implementation/sizeof/README.md)
     5. [Aligned Malloc](Data_Struct_Implementation/alignedMalloc/README.md)
     6. Malloc()
     7. [strstr()](Data_Struct_Implementation\strstr\Makefile)
-17. Concurrency 
+12. Concurrency 
     1.  Implement a Spinlock/Mutex
         1. [Test-and-set](https://en.wikipedia.org/wiki/Test-and-set) 
         2. [Compare-and-swap](https://en.wikipedia.org/wiki/Compare-and-swap)
@@ -85,14 +94,14 @@
     7.  [Print In Order](Data_Struct_Implementation/concurrency/PrintInorder.md)
     8.  [Building H2O](Data_Struct_Implementation/concurrency/BuildingH2O.md)
     9.  [The Dining Philosophers](Data_Struct_Implementation/concurrency/TheDiningPhilosophers.md)
-18. Other Implementations
+13. Other Implementations
     1.  Shuffle cards
     2.  Accurately (emphasize) read 64bit register with read32
     3.  Given a matrix and its center coordinates, draw the circle
     4.  Find a 32 bit frame start sequence in a raw byte stream buffer
     5.  Memory tracker to hook into glibc library to keep track of dynamic memory allocations, including statistics
     6.  Given an array of angles and an array of voltages for these angles, now there is a new angle coming in, calculate its voltage.
-1.  [Other Common C algorithm](https://github.com/fragglet/c-algorithms)
+14. [Other Common C algorithm](https://github.com/fragglet/c-algorithms)