Add General Purpose Input and Output Pins to your Laptop/Desktop through your USB Port.

In this repository you will find all the resources needed to add gpio to your PC.
To make things work together perfectly, I have written a Device Driver Library which you can include in your program. It will make programming the gpio similar to the Arduino Environment, which is more user-friendly.

Currently works perfectly with AT90S2313 Microcontroller

1. I/O Port Programming
2. SPI MOSI as Master

This repository consists of a driver program for working with the USB CDC Devices.
The driver program is split up into two parts, the Crawler and Util respectively.

The crawler part contains the main function to make your logic work. It is used to call functions from the util part to handle various kinds of stuff. It can be found inside the src/ directory.

The util part is where the real magic happens. It consists of functions, which reside inside a library, libusb. The libusb is a static library. It can be found inside the util/ directory.
There are four types of functions defined inside the library. These are as follows:

1. Serial Communication functions
2. Pin Manipulation functions
   2.1 Pin & Ports Definintions
   2.2 Helper Functions
   2.3 Pin Initialise, Read and Write Functions
3. Advance Features
4. Addon functions and Macros

Each of these functions carries the importance of their own. Let's understand what each of these functions performs.

These are at the lowest level in the function hierarchy. These functions facilitate the use of serial communication protocol in our program. These functions are mainly based around the terminos library.
Functions included are:

1. Baudrate Array Definitions

• baudrate_to_index[]
• index_to_baurate_const[]

2. Macros

• baurateToIndex(int (Index))
• indexToBaudrate(int (Baudrate))

3. Serial Communication Functions

• int(File Descriptor Return) open_serial_port(const char* (Port Name),unsigned int (Baudrate))
• int(Success(0) or Error(-1) Return) serial_write(int (File Descriptor),const char*(Data to write))
• int(Register Value or Error(-1) Return) serial_read(int (File Descriptor))
• void close_serial_port(int (File Descriptor))

Error message of -1 is returned from each of the function at the time of encounter. Expect for close_serial_port()

These functions are bulit on the top of the Serial Communication function. The primary purpose of them are to change or read the logic level. The make of these functions are built around the most popular Arduino Source Code.
Functions included are:

1. Pin and Port Array Definitions

• port_to_mode[]
• port_to_output[]
• port_to_input[]
• digital_pin_to_port[]
• digital_pin_to_bit_mask[]

2. Helper Functions

• int(Status of the register or Error(-2) Return) get_reg_info(int (File Descriptor),uint8_t(Register Address))
• int(Success (0) or Error(-2) Return) set_reg_info(int (File Descriptor),uint8_t (Register Address) ,uint8_t (Value to Write))

3. Pin Initialise, Read and Write Functions

• int(Success(0) or Error(-3) Return) init_board_port(int (File Descriptor))
• void pinMode(int (File Descriptor),uint8_t(Pin Number),uint8_t(Mode: INPUT,INPUT_PULLUP,OUTPUT))
• void digitalWrite(int (File Descriptor),uint8_t(Pin Number),uint8_t(State:HIGH or LOW))
• int(Value:1 or 0) digitalRead(int (File Descriptor),uint8_t(Pin Number)

Error message of -2 is returned at the time of encounter.

pinMode(), digitalWrite() and digitalRead() have inbuilt security feature. If the crawler program asks for a pin which is used for other usage apart from the I/O then the functions are not EXECUTED. They are returned with a warning message. Example includes use of pins such as Reset, XTAL1, XTAL2, VCC and GND

BitBanged SPI Interface is supported by the devices. Currently only Master Out and Slave In communication is working. Work is still left for Master in Slave Out. Example of SPI can be found inside src/spi.c.
Functions Included are:

• uint8_t(Hex Value Return) asciitohex(char (ASCII Character))
• uint8_t(MISO Received Data) spidata(int (File Descriptor),uint8_t(MOSI Pin),uint8_t(MISO Pin),uint8_t(SCK Pin),const char*(Data to be sent))

These are in the used for extending the functionality of the library. These are really simple and basic functions to make life much easier.
Functions and Macros included are:

• min(a,b)
• max(a,b)
• round(x)
• sq(x)
• radians(deg)
• degrees(rad)
• void printf_d(const char*,uint8_t)
• void printf_d_v(const char*,uint8_t,uint8_t)
• void delay(int)

To enable the Multithreading, make the #define MT 1 in util/libusb.h To use threading, the library provides standard calls to the pthread.h library. It uses a MUTEX named as serial_port_mutex for making the serial_port accessible to either of the thread.

To get an idea about the threading see the example in src folder thread.c. It shows how to the threads can access each pin independent of what the other thread is doing.

For custom made source code place them inside the src folder or else you need to make changes in the makefile.
To compile the source code just run with make command. It will automate all the neccessary task. Errors will be displayed at each stage if encountered. Inside the master directory:

To build a particular "file.c" inside the src folder do,

make Target=file

Eg.

make Target=program
or
make Target=thread

To run the executable do,

sudo ./file

Eg.

sudo ./program
or
sudo ./thread

To remove the executable "file" do,

make clean Target=file

Eg.

make clean Target=program
or
make clean Target=thread

To disable the Debugging Print Statements make #define DP 0 from 1 in util/libusb.h, this will make all logs to disable.

• SPI Communication as MISO
• I2C Communication
• Other Internal Registers access

For more details visit the following links:

1. http://www.recursion.jp/prose/avrcdc/cdc-io.html For CDC Device Firmware
2. https://www.cmrr.umn.edu/~strupp/serial.html For Serial Communication in POSIX