Christopher Delgado

Richard Prego

Matthew Neuteboom

Ron Puertollano

Timothy Pirog

Design VI – Homework 6 April 13, 2012

Section 1 – Group Member Responsibilities

This report is comprised of the functional description of our design of a gamepad add on for smartphones. The summary of assignments for each group member is as follows:

· Christopher Delgado: Responsible for SWOT Analysis of Chosen Design (Section 2.5)

· Richard Prego: Responsible for Implementation Block Diagrams and their description (Section 2.1)

· Matthew Neuteboom: Responsible for Possible Solutions to Design Constraints (Section 2.2)

· Ron Puertollano: Responsible for Multidisciplinary Teamwork Planning (Section 2.4)

· Timothy Pirog: Responsible for Ethical and Professional Responsibilities (Section 2.3)

Section 2 – Functional Description of Smartphone Gamepad Add-On

Section 2.1 – Implementation Block Diagrams

Implementation Block Diagram #1

Inductive Charging Circuit – The circuit is made up of analog components (resistors, capacitors, inductors, etc.) whose values cannot be accurately determined at this stage in the project. The component values will need to be calculated and tested through several iterations before a specific optimal design can be chosen. This circuit will provide between 4.25 and 6 V at 200 to 600 uA to the LTC4057-4.2 Li-Ion Charging IC to charge the built-in battery.

Generic Mini-USB Connector – A generic mini-USB connector that would allow charging via USB cable from a PC or USB AC/DC charger. The mini-USB connector would provide the 5 V power provided by the USB connector to the LTC4057-4.2 Li-Ion Charging IC to charge the built-in battery.

LTC4057-4.2 Li-Ion Charging IC – The Linear Technology LTC4057-4.2 IC is specifically designed to work within USB voltage ranges. The charging IC provides constant-voltage/constant-current charging to lithium-ion rechargeable batteries. It operates on very low shutdown current and requires few external components, making it ideal for portable applications, such as a phone gamepad add-on.

Generic 4.2 V Li-Ion Battery – A generic Li-Ion battery is used to power the microcontroller, Bluetooth module, and other components in the system. The charge rating for the battery would need to be selected after testing the design to determine how much the average power load on the battery would be, and would be selected to ensure long use times between charges.

Generic Push-Button Switches – Eight push-button switches are needed for the implementation of a four-way directional pad, and four buttons (for example: A, B, X, Y). These switches could be either normally-open or normally-closed switches, and would be connected to the microcontroller by one wire per button. Each one would connect to a digital input pin on the microcontroller.

PIC18F14K22 Microcontroller – The PIC18F14K22 microcontroller features 16 kB flash program memory, and 18 I/O pins. It operates at a clock rate up to 64 MHz, and operates under a wide supply voltage (2.3 to 5.5 V). It interfaces with the BLE112-A Bluetooth Module via a SPI bus. The microcontroller would handle converting button presses to commands to send over the Bluetooth connection to the phone.

Bluegiga BLE112-A Low-Energy Bluetooth Module – The BLE112-A handles all of the Bluetooth communication with the phone. The module is small and low-power, making it ideal for mobile applications, such as a phone game controller. It interfaces with the microcontroller via a SPI bus.

Status LEDs – Various colored LEDs will show the system status, such as power on/off, charging, pairing status with the phone, etc.

Implementation Block Diagram #2

Inductive Charging Circuit – The circuit is made up of analog components (resistors, capacitors, inductors, etc.) whose values cannot be accurately determined at this stage in the project. The component values will need to be calculated and tested through several iterations before a specific optimal design can be chosen. This circuit will provide between 4.5 and 6 V to the LP3947 Li-Ion Charging IC to charge the built-in battery.

Generic Mini-USB Connector – A generic mini-USB connector that would allow charging via USB cable from a PC or USB AC/DC charger. The mini-USB connector would provide the 5 V power provided by the USB connector to the LP3947 Li-Ion Charging IC to charge the built-in battery.

LP3947 USB Li-Ion Charging IC – The National Semiconductor LP3947 IC is specifically designed to work within USB voltage ranges. The charging IC provides constant-voltage/constant-current charging to lithium-ion rechargeable batteries.

Generic Push-Button Switches – Eight push-button switches are needed for the implementation of a four-way directional pad, and four buttons (for example: A, B, X, Y). These switches could be either normally-open or normally-closed switches, and would be connected to the microcontroller by one wire per button. Each one would connect to a digital input pin on the microcontroller.

CC2540 Bluetooth System-on-a-Chip – The TI CC2540 Bluetooth System-on-a-Chip integrates both a microcontroller and Bluetooth module into one chip. It features 128 kB flash program memory, and 21 I/O pins. It operates at a clock rate of 32 MHz, and operates with a supply voltage up to 3.9 V. The built-in microcontroller would handle converting button presses to commands to send over the Bluetooth connection to the phone. The Bluetooth section of the IC would send the commands over the Bluetooth connection.

Status LEDs – Various colored LEDs will show the system status, such as power on/off, charging, pairing status with the phone, etc.

As all components are hardware, connections between them will be electrical wire. The difference between the two designs is the Li-Ion Battery Charger used and the manner in which the Bluetooth module and microcontroller are implemented. Our “best” design would be the one described in block diagram #2 as the Bluetooth system on a chip has a lower cost than the module and microcontroller combined and creates a simpler overall design as you would not need to be dealing with two separate components but one. The Li-Ion Battery IC in diagram #2 is also less costly despite possibly requiring additional external components (unlike the IC in diagram #1). See the appendix for links to component datasheets.

Section 2.2 – Possible Solutions to Design Constraints

Economic constraints: The manufacturing cost must be less than its market price in order to turn a profit. Competing products that will soon be on the market will cost roughly $60 (and upward). The market price for our product should compete with this price. Prototyping for the project will most likely be cheap enough to be done on the budget provided by the school. Further funding will most likely come from game companies interested in seeing the product succeed.

Environmental Constraints: Product will be composed of mostly recyclable material. Product should conform to the Restriction of Hazardous Substances Directive (RoHS) in order to be sold in Europe. The directive restricts the usage of the following six substances: Lead, mercury, cadmium, hexavalent chromium (Cr6+), polybrominated biphenyls (PBB), polybrominated diphenyl ether (PBDE). PBB and PBDE are flame retardants used in several plastics. Plastic used to create controller casing should be made of recyclable plastic. Battery must also be recyclable.

Health and Safety Constraints: Ensure that rechargeable Lithium ion battery does not overheat or explode during use or charging. Product must ensure that battery stops charging once full. Product may contain small parts, so a warning should be properly displayed on the product's packaging as well as somewhere on the product.

Manufacturability: There are three major components to the project which must be individually manufactured and then assembled:

· Circuit board fabrication: PCBs can be prototyped in fabrication houses for around $25-$50 per board. However, low costs only come with mass production. There are thousands of services out there which offer both, and as such, costs are very competitive. Schematics can usually be uploaded via the internet.

· Components: Primary components will be a Bluetooth controller, a microprocessor, a battery, an induction coil, a rectifier, pressure sensors for the various buttons, and LEDs. The Bluetooth radio, the microprocessor, and the battery will have the largest costs - the other components can be ordered cheaply in bulk. The best place to order these in bulk is through the manufacturer via printed or online catalogues. The ECE department most likely has a large stack of parts catalogues available for our use. Otherwise, manufacturers such as 3M provide free online catalogues.

· Plastic fabrication: The shell and the buttons of the product will be made out of some sort of cheap and durable plastic. Plastic fabrication can similarly be done at fabrication labs located around the country. Also, the rapid prototyping lab located in Carnegie laboratory should be useful in creating the first prototype for our project.

Sustainability: Product should be under factory warranty for one year. Bluetooth operates in the unlicensed ISM 2.4GHz short-range radio frequency band, so no license will be needed for the product.

Section 2.3 – Ethical and Professional Responsibilities

Warranty: From a professional and ethical stand point we would like to offer a warranty to ensure to our customer that if something was to go wrong we will replace or refund if nessciary. If we build a quality device, a warranty of 90 days will not cut too much into our profit because there should not be too many problems.

Ergonomics: We as professionals do not want out device to injury our customers during short or long term use so we will test and make sure that it does not cause any problems under normal use. This will require test cases and testers to ensure the quality of our produce. If something is found to be problematic we will look to change the design accordingly.

FCC Regulations: If we want our device to be sold in the United States we will have to have Class A&B FCC certification because our system will be used both in commercial and home settings. Our project fits under, FCC Certified Peripherals and Add-On Cards. Most peripherals (disk drives, floppy drives, CD-ROM drives, tape drives, etc.) have their own FCC certification, so our add-on will have this, so it can be sold separately. They would technically not need to be certified separately if the system in which they are installed is certified as a unit. Once a system has passed FCC certification, a manufacturer may swap or add FCC certified cards and peripherals and they retain compliance even though the system may technically exceed the limit with the different peripherals.

Section 2.4 – Multidisciplinary Teamwork Planning

There are three disciplines that could be useful for the design of our Game Pad Add-on. A computer science or computer engineer will be necessary for the programming of the device. An electrical engineer will be needed for the circuit consolidation of the device. And a mechanical engineer is necessary for the construction of the device.

Computer Science/Engineer: A computer programmer who understands the interface and application development of iPhone and Android devices, and Bluetooth 2.0 interface. The programmer will need to be able to program the two platforms in order to 1. Communicate with our gamepad add on and 2. Be able to replace constraints set by the two devices to be able communicate with current applications. The algorithms of the program must be efficient as possible. The device is relatively small and the battery is not unlimited. The longer the coding for the device and the way the algorithms function will have an effect of current drain of the battery.

Electrical Engineer: For our game pad design, an electrical engineer will be necessary in the design process. Advance knowledge of wireless communication, microelectronic circuits, and power engineering will be necessary. The electrical engineer with the background in wireless communication will help implement the way the game pad and the device communicate. Our design uses Bluetooth technology. The game pad also implements inductive charging. An engineer who understands power engineering will be necessary. They must be able to implement a charging method that will make the device power efficient while still maintaining the grounds set by IEEE 802.15 work group 1 and 5. These work groups are in charge of setting the requirements for WPAN / Bluetooth and Low Rate WPAN. A liaison for how the three correspond with each other will also be necessary. For example, Bluetooth technology that corresponds with the game-pad add on may give on noise at a low frequency that will interfere with the microcontroller. The electrical engineer will also be responsible to make sure the device follows all FCC rules.

Mechanical Engineer: Our design uses plastic parts to latch onto the device will be necessary. Understanding of CAD modeling or SolidWorks will be necessary. Our design will require construction of the device according to the specifications of the platform: Android or iPhone devices. The mechanical engineer will create a 3D design to be manufactured through Plastic Injection Molding. Expansive knowledge of materials processing will be necessary. The mechanical engineer will also be responsible in the collaboration of inductive charging and Bluetooth communication with the mechanical design. Some problems with the iPhone 4 and Android ASUS Prime was wireless communication problems. The material of the game pad add on must not interfere with the both the inductive charging of the device and the wireless communication of the circuitry.

Section 2.5 – SWOT Analysis of Chosen Design (Block Diagram #2)

Strengths

1. Ease of Implementation. The design is relatively easy to implement as many of the components are “drop in” components that connect and communicate with each other easily.

2. Cost & Availability. The cost of the project is very feasible. There are no budget breaking components, and all of them are readily available from online retailers such as Digikey.

3. Game Controls. Theoretically, any in game controls for a game on a smartphone can be mapped to the gamepad, and the Bluetooth system on a chip will be able to make that a reality.