NOTICE: The Processors Wiki will End-of-Life in December of 2020. It is recommended to download any files or other content you may need that are hosted on The site is now set to read only.


From Texas Instruments Wiki
Jump to: navigation, search
RF-PID Quick-Description.

Chronos RF-PID

The Radio Frequency Personal Inventory Device (RF-PID) is an application of the EZ-430 Chronos watch that utilizes the built in transceiver of the CC430 to allow the user to keep track of small personal items. For this project the Chronos is used as a central hub which communicates with several "node boards" attached to items such as a wallet, keys, phone, or even remote control for a television. When an item is missing the user can use the watch to activate a blinking light, produce a tone on a speaker and activate a vibrating motor to help the user find the missing item. RSSI information from each missing device will be used to indicate the physical distance from each missing item. As a person gets closer to the missing item(s), the light, speaker and motor will flash faster and faster. Once the person is within a certain distance of each item, the flashing light and speaker tones will stay on. This will tell the user that the missing item is within a certain perimeter.

Demonstration & Voting
For more information or to see a live demonstration of the RF-PID please visit the Coop Design Challenge Demonstration on August 5th, 2010. To-scale replicas of the RF-PID node boards will be on display to demonstrate product form factor on various personal items. Voting starts August 2nd and ends August 5th.

Functional Description

The Chronos watch acts as the master device for the RF-PID system. The watch itself is based on the CC4306137 micro-controller which features an RF transceiver module that operates at 915 MHz. The nodes, or daughterboards, also use the same CC4306137 micro-controller with matching RF transceiver module. When the watch sends a packet the nodes will catch the packet and turn on a light, start a vibrating motor, and activate a small speaker to help the user of the watch find the missing item. Additionally, after the nodes receive a packet they will send the RSSI information for receiving the packet back to the Chronos watch. With this information the watch will approximate the distance the missing item is from the watch. A menu built into the watch will allow users to add new RF-PID modules and assign names to each device. In this way, the user can simply scroll through a menu, choose whatever item they are looking for and locate it quickly without having all of the modules activated at once. {{#evp:youtube|wCKr1GcRvvQ|RF-PID Range Demonstration|right}}


Our graduate professor, D.Y.C. Lie at Texas Tech, has said that for a product to be marketable it has to help a pain that people experience. Cellular telephones cure the pain of being cut-off from your loved ones, GPS devices remove the pain of ever feeling lost, and RF-PID removes the possibility of ever losing any of your day-to-day items. Today the average person leaves the house carrying more items than they may have ten years ago; mp3 players, cell phones, keys, wallet, leatherman/knife, thumb drives, etc. Many of these items are very easily lost and finding them usually has to happen in a hurry. This product offers a quick time-saving solution to finding your missing items before being late to your next destination.

The final product would aim to be very small and inexpensive so that people could purchase new RF-PID nodes to monitor new devices. The Chronos watch could "learn" to communicate to new devices by synchronizing with a the newly purchased node and assigning it a name, similar to a universal television remote control.

Future Developments

Due to financial and time constraints there are many ideas leftover that could be implemented to enhance this project. As it stands, the project was completed on a budget of $0.00. All components were taken from spare parts around various labs at Texas Instruments, free samples, and discarded cell phones. With an expanded budget and additional time the following goals could be achieved;

  • A PCB has been designed for the nodes/daughterboards that would significantly add to the form factor and practicality of these devices. If size continues to be a problem after PCBs are implemented, MEMS motors could replace the current vibrating motors and perhaps small piezo speakers built on silicon to replace the current speakers.
  • Add an "identifying" byte to the packet protocol to incorporate more devices that can individually trigger, instead of all the nodes responding at once. (i.e. "Wallet" is device 0001, "Keys" are 0010, etc)
  • Integrate modes to the watch:
    • Quick Polling - The watch quickly polls each device and based on an RSSI strength threshold determine if the item is "on your person" or not
    • Find Object - The watch tells an individual item to turn on its light, motor, and speaker to help the user find it.
  • Speaker pulses faster/slower based on your distance from the node


"Q-Watch" from GoldenEye 007 for Nintendo 64

In brainstorming ideas for this contest the members of the project initially came up with a collection of plausible ideas before simply asking friends and co-workers the simple question; "What would you like for your watch to do?" After ciphering through the collected ideas the most commonly requested feature was some sort of inventory management device.

The highest level of success for this product would be to develop something reminiscent of the "Q-Watch" from the 1997 classic first person shooter "GoldenEye 007" for the Nintendo 64. If the player pressed pause during the game the graphic would represent looking straight into the watch where you could do various game management tasks - like save your game. In addition however the watch also acted as an inventory management interface for the game. From this screen the player could view what weapons, gadgets, keys, and other items James Bond had on him at that moment.

The other side of inspiration for this project was considering what the goal of the project was from the perspective of Texas Instruments. The design contest, and the Chronos watch itself, are designed to showcase the capabilities of the CC4306137 and other micro-controllers in the family. While the watch itself does package cool toys, like accelerometers, we wanted to try and focus on the micro-controller itself and demonstrate an application that shows off how easy it is to use a CC430 and its RF capabilities to develop new products with minimal time to market.

"Failed" Ideas

  • Chronos Theremin - Too bad someone already beat us to it
  • Home Control Watch - The watch controls various features of the average home; blinds, coffee maker, television, stereo, computer, etc. etc.
  • Chronos RC-Plane Control - Remote control for an RC airplane based on accelerometer data from the watch -- FAR too dangerous
  • "Jersey Shore Fist-pumping Volume Control" - Control volume of a stereo by "fist pumping" with various level of excitement to raise or lower the volume -- FAR too ridiculous
  • Wireless Guitar "Wammy" Bar - Similar to the "hot hand" that already exists, but with the Chronos watch -- FAR too Dragonforce

Source Code

The source code for this project is a heavily modified pair of applications based on the "RF-Toggle_LED_Demo sample project. The code was designed to allow for two CC4306137 EVMs to communicate back for forth, each turning on an LED on the other. Additionally the sample code facilitates briefly blinking a single LED on the transmitting board to indicate that a transmission has occurred. The sample project was modified on the node boards to toggle a brighter LED and turn on a vibrating motor. The node source code also drives the speaker by pulsing a square wave out of a pin on the CC430 and into a Class D audio amplifier that in turn drives the speaker. The pulses driving the speaker produce odd harmonics to generate a sound that is maximally irritating to the human ear, so as to get the attention of the user of the watch. The code to drive the node boards was developed first and then ported to the Chronos Watch which uses the same micro-controller and transceiver architecture as the CC4306137 EVMs. The code was modified for the watch to listen to different sources for transmit interrupts and provide feedback on the state of the watch to the user of the watch via the first line of segments on the LCD screen. The Watch code also displays RSSI information on the second line of segments on the LCD that helps the user know the distance from their missing item. Source code for this project is divided in two sections; code for the nodes, and code for the watch. The code for RF-PID node boards and watch are available at the link below. For other necessary header files, please contact one of the group's engineers.

RF-PID Source Files


A 1"x1.5" board was designed for the node/daughter boards used in the RF-PID project. Due to time constraints and in the interest of conserving money used in this design contest the boards were not manufactured. The schematic and layout, however, are available for viewing either in PDF or JPEG formats below. Gerbers can be attained by emailing Cliff Schecht.

Schematic Images:
PDF Downloads:

RF-PID Schematic
RF-PID Board Layout Top Layer
RF-PID Board Layout Bottom Layer
RF-PID Board Layout No Fill



Texas Tech University

Wreck 'Em!