RC4 Servo Monitor & Controller

RC4 can act as either a 5-channel R/C signal sampler, or as a 4-channel servo controller, or both! Each of the four primary channels can be configured independently for different modes of operation. An additional programmable fifth input channel (known as the "Trigger Input") is available for triggering various events based on the input signal. A host processor/controller can also monitor this signal to provide triggering options of its own.

Commands and data are exchanged across a serial interface, operating reliably at speeds up to 57600 bps, allowing a host processor to monitor the input signals and/or control the output signals.

The original idea for this device was born in the early 1990s. The first attempt at developing what was then a very crude, bulky, rudimentary version of the device, consisted of six descrete integrated circuits that did nothing more than switch between radio control and some circuitry that provided preset signals to fix the servos in a known position when input signal was lost. The current version was conceived late in 2001 and has been in active development since June 24, 2002. It consists of two PIC microcontrollers and provides an extended variety of useful functions and features.

The first-iteration prototype (Revision A) was successfully flight-tested on April 15, 2003. The flight demonstrated the high degree of reliability of the device, plus helped in the continued development and refinement of its core operational features. One aspect of this testing revealed that the command structure of the device was in need of revision to make it more useful and intuitive. Development work since then has focused on not only improving upon the user interface, but also adding a few new features to increase the flexible, yet robust nature of the device.

RC4 is packed full of rich, useful features - more than you may need for any one particular application. This is because, during the development of RC4, it became clear that the device could be used in many applications, such as robotics. In fact, as a member of the Home Brew Robotics Club in San Jose, CA, and a fan of Wayne Gramlich's RoboBRiX, I decided to give RC4 a RoboBRiX interface to allow it to be controlled by a RoboBRiX master hub.

Since RC4 was not developed, specifically, as a RoboBRiX module, the hardware dimensions do not conform to RoboBRiX specifications. However, an official RoboBRiX version may be produced in the future. Also, the hardware design will be open-source so that any third party can produce a board of their own design and dimensions. The software will remain proprietary, however, and pre-programmed chips will be available exclusively through CodeSmart. Licensing options have not been formalized at the time of this writing, but details will be disclosed as soon as they become available.

Among the many features of RC4 is its ability to deliver data either in a burst mode of operation, where all the data in response to a command is delivered in a continuous stream, or in a byte mode, where the host can request each successive byte as needed. This enables slow or unbuffered host processors/controllers to extract information at whatever rate is required.

See below for documentation and current status of the various RC4 revisions, or you may review the RC4 fact sheet to get an overview of RC4 features.

Documentation and Status

Below is a list of the current revisions to RC4. You may notice the RC4 device version jumps from Revision A to Revision F. Revisions B through E represent different versions of the RC4 mainboard design. The reason there is no information provided here about these versions is because boards for those revisions were never physically produced. The version G design has been completed and is now at the heart of the RC4 test bed while Revision F documentation is completed.

Revision A - Obsolete (don't waste your time): The first version of RC4.
Revision F: The second physical version of RC4.
A far cry from Revision A. Documentation currently being finalized.
Revision G: The Revision G boards have arrived! But Revision F is not entirely wrapped up, yet.
Current Status:: Nothing has happened for over a year
Firmware development is frozen (PIC1 Version 2.2 & PIC2 Version 2.2).
Formal test plans are being defined.
RC4 soon to be installed on a mobile ground vehicle (see The Trike) for field testing.
RC4 installed inside a unit with an embedded computer for rigorous preliminary testing (to begin soon).
RC4 revision F base documentation nearing completion.
RC4 revision G boards have arrived!
RC4 testing will proceed on Rev. G board following Rev. F development freeze.
RC4 [officially] turned four years old! (06/24/2006)

For questions or comments about RC4, please write to rc4@codesmart.com.