Interfacing PS2 Controller with Arduino

    In the previous post PS2 Controller Outline, the pin configuration, specifications and working of different buttons of PS2 controller are explained. In this post we interface the controller with an Arduino development board and test a sample program. We seperate this into two sections; the hardware and software sections. The hardware section is pretty much straight forward which involves connecting controller wires to arduino pins. In the software section, we use the PS2X class in "PS2 controller Arduino Library v1.4" provided by billporter.

Hardware Section:

    Out of 9 wires from the PS2 controller, we here use only 6 pins. They are Vcc(red), gnd(black), clock(blue), command(orange), attention(yellow), data(brown).

PS2 Controller Pins	Arduino Pins
Vcc	3V3 pin of on-board FTDI chip
gnd	digital ground pin
*clock	pin 13
*command	pin 11
*attention	pin 10
**data	pin 12

    * Note1: clk, cmd, att, data can be connected to any of the digital pins and program can be modified accordingly.

  ** Note2: The data pin should be connected as shown in the figure

Software Section: 

    The library is available for download at billporter. In the PS2X class, all the button states are defined as constants as given below:

Some of the important functions defined are given below:

1. config_gamepad(clock,command,attention,data,Pressures?,Rumble?)

                 This function configures the PS2 controller and returns a corresponding result in byte format. The pins to which clk, cmd, att and data are connected should be entered in this function for initial setup. Pressure and Rumble are boolean values which can be enabled or disabled.

2. read_gamepad()

                This function is called to get new values from the controller. This should be called atleast once in a second. It can also be used to set vibration strength of the vibrating motor.

3. Button(Button_Constant)

                This function returns a boolean value depending on whether a button is pressed or not. It takes a button constant as argument.

4. Analog(Button_Constant)

                This function takes Button_Constant as argument and returns a byte which represents the analog value of the button (ie) the position in case of stick and the pressure with which the button is pressed in case of pressure button.

5. ButtonPressed(Button_Constant)

                It returns a boolean value based on whether a button is just pressed or not.

6. ButtonReleased(Button_Constant)

               It returns a boolean value based on whether a button is just released or not.

7. NewButtonState(Button_constant)

                             It returns a boolean value based on change in button state.

Sample Code:

    Having discussed the software and hardware sections, lets now examine the example code given in the library itself. Click here to view the sketch "PS2X_Example".

ALGORITHM:

• Include PS2X_lib.h
• Create an instance for PS2X class

SETUP:

• Set baud rate
• Configure the game pad
• Identify the controller type 
• Display results in Serial Monitor

LOOP:

• Read game pad ( read_gamepad( ) )
• Check all the button states 
• If any button is pressed, display it in serial monitor
• If L1 or R1 is pressed, display the analog stick values in serial monitor
• Call a delay of 50 milliseconds.

Screenshot of serial monitor:

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8255 Programmable Peripheral Interface

         In this post, we are going to learn a very old grand father of modern processors, named 8085 and his colleague 8255.

Pins, Signals and internal block diagram of 8255: 

•  The internal block diagram of 8255 is shown in fig: 
•  The 8255 can be either memory mapped or I/O mapped in the system. In the schematic shown in above is I/O mapped in the system. 
•  Using a 3-to-8 decoder generates the chip select signals for I/O mapped devices. 
• The address lines A4, A5 and A6 are decoded to generate eight chip select signals (IOCS-0 to IOCS-7) and in this, the chip select IOCS- 1 is used to select 8255. 
• The address line A7 and the control signal IO/M (low) are used as enable for the decoder. 
• The address line A0 of 8085 is connected to A0 of 8255 and A1 of 8085 is connected to A1 of 8255 to provide the internal addresses. 
• The data lines D0-D7 are connected to D0-D7 of the processor to achieve parallel data transfer. 
•  The I/O addresses allotted to the internal devices of 8255 are listed in table. 

              It has 40 pins and requires a single +5V supply.  The INTEL 8255 is a device used to parallel data transfer between processor and slow peripheral devices like ADC, DAC, keyboard, 7-segment display, LCD, etc.  


               The 8255 has three ports: Port-A, Port-B and Port-C.  Port-A can be programmed to work in any one of the three operating modes mode-0, mode-1 and mode-2 as input or output port.  Port-B can be programmed to work either in mode-0 or mode-1 as input or output port. 
               
               Port-C (8-pins) has different assignments depending on the mode of port-A and port-B. If port-A and B are programmed in mode-0, then the port-C can perform any one of the following functions. As 8-bit parallel port in mode-0 for input or output. As two numbers of 4-bit parallel ports in mode-0 for input or output. The individual pins of port-C can be set or reset for various control applications. 


               If port-A is programmed in mode- 1/mode-2 and port-B is programmed in mode-1 then some of the pins of port-C are used for handshake signals and the remaining pins can be used as input/ output lines or individually set/reset for control applications.  The read/write control logic requires six control signals. These signals are given below:

1. RD (low): This control signal enables the read operation. When this signal is low, the microprocessor reads data from a selected I/O port of the 8255A. 
2. WR (low): This control signal enables the write operation. When this signal goes low, the microprocessor writes into a selected I/O port or the control register. 
3. RESET: This is an active high signal. It clears the control register and set all ports in the input mode. 
4. CS (low), A0 and A1:  These are device select signals. They are, Interfacing of 8255 with 8085 processor:     

Simple schematic for interfacing the 8255 with 8085 processor

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