Project Details

Background

Augmented communication devices (ACDs) are commonly used to help people with disabilities communicate. The motivation of young children to learn how to use their ACDs is usually fairly low. They have grown used to their parents being able to handle their needs without communicating verbally. Toys are used as tools to provide the motivation to learn how to work with ACDs. Currently, only IR toys can communicate with ACDs. Unfortunately, IR toys are generally expensive and not widely available. The selection of IR toys is limited and unexciting for the children compared to RF toys. There is currently no device to interface RF toys with ACDs.

Problem Statement

The goal of tis project is to create a device to interface a wide selection of RF toys with ACDs.

System Diagrams

The system diagrams, shown below in Figures 1 and 2, illustrate the top level of our design. Our device acts as the translator between different interfaces. To configure our device, the user presses a button on our device that puts it in the learning mode. While in learning mode, illustrated in Figure 1, the user presses a control on the RF remote. Our device detects this signal and stores the relevant information in the active profile. Our device then sends out an IR signal so that any device with an IR learning capability will receive a signal to learn. This process is shown in Step 1. Optionally, while receiving an RF signal, if our device receives a USB signal, as shown in Step 2, this signal will be associated with that RF signal in the profile. This allows any Windows based computer with USB, but without IR, to control our device. This sequence will be repeated for all control modes desired for the RF remote.

Learning Mode
Figure 1: Learning Mode

Once the learning process is finished, a button will be pressed on our device to put it back into the operating mode. In this mode, shown in Figure 2, if our device receives an IR or USB signal previously associated with an RF signal in the learning mode, it will reconstruct the RF signal from the saved data and transmit it. This process allows the user to control an RF toy with an ACD or other Windows based device with USB.

Learning Mode
Figure 2: Operation Mode

Requirements

Mechanical Requirements

The mechanical requirements for the device include portability and durability. In terms of portability, the device should be easily carried along with the augmented communication devices (ACDs). Currently, the most portable ACDs are easily carried with one hand. The device should be able to be mounted to ACDs using a method such as Velcro. As for durability, the device should be resistant to human abuse. This includes the device being thrown against walls or dropped from a reasonable height. This is because the children that will be using the device often develop impaired social interaction skills, which are reflected in physically throwing objects within reach.

Table 1: Electrical Specifications
Specification Value
Maximum Weight (without batteries) 2 lbs.
Maximum Size (witout antenna) 3 in x 3 in x 1 in
Maximum Shock 5 G

Electrical Requirements

The electrical requirements are broken up into power requirements and interface requirements. The power requirement is that the device must be powered from either the USB interface or batteries. The ACDs will communicate with our device via either USB or IR. The RF interface shall learn signals in the common RF toy frequency bands specified in Table 2. The learning functionality needs to handle a bit rate sufficient to learn any RF toy.s modulation scheme and data sequence.

Table 2: Electrical Specifications
Specification Value
Recommended Operating Voltage 5 V for USB, or 7.2 V from 6 AAs
Maximum Operating Voltage 20 V
Frequency bands 27 MHz, 49 MHz, and 72 MHz
Modulated bit rate 500 kbps
Maximum data-stream length before repeat 1 s

Documentation Requirements

For documentation, there will be two documents created: a non-technical user.s manual for the enduser, as well as a technical manual for product maintenance. The non-technical user.s manual will include instructions for operating the device. There will also be a toy compatibility list describing our device.s ability to communicate with different RF toys. The manual for product maintenance will include the technical details of the design. There will be a section for RF related interfacing, as well as a section for the interface to the ACDs. The toy compatibility list will be duplicated from the non-technical user.s manual with the addition of an explanation of why certain toys do not work.

Code will be kept in a Subversion repository and will be well documented. All code will also go through a rigorous design review where someone else will make sure that the code makes sense with the comments provided.

Testing Requirements

During the project design, testing of the interface requirements will primarily take place using personal computers, which have similar interfaces to the ACDs. Other testing will focus on the mechanical and RF aspects of the project. The mechanical aspect is the ability of the device to withstand abuse, such as being dropped. RF testing will center on electromagnetic interference (EMI) and electromagnetic compatibility (EMC). The device must also comply with all Federal Communications Commission (FCC) regulations, specifically Part 15.

The final testing of our device will be conducted on the PRC ECO-14, PRC VT-2 and DV-5 ACDs (contingent on availability), using both the IR and USB interfaces, where available. Three different RC cars and one other RF toy will be used to test the RF learning capability. Finally, our device will be tested in a classroom by actual children that would use this product. Parents or teachers will operate the learning functionality between the device and the ACD.

General Requirements

The general requirements involve reliability and operation. The reliability will be measured by the mean time between failures (MTBF). The operation of the device consists of two aspects: learning RF and the interface to the ACDs. When learning RF signals, the device should be able to save settings to a specific profile for a given toy. These profiles can be named.

Table 3: General Specifications
Specification Value
Mean Time Between Failures 1 month
Number of profiles 8

Manufacturability Requirements

This project has the potential to interest the manufacturers of the ACDs, so the manufacturability of our final design must be considered. To accommodate this, the design will use surface mount components wherever possible. These components will all be commercial-off-the-shelf (COTS) parts. Finally, a printed circuit board (PCB) design, using the surface mount components, will be created.

Last updated: April 16, 2008