Circuit Lake

Electronic Project and Circuit Collection

Specific Area Message Encoding Test Generator

05/07/2010 Category: Alarm, AVR, Project, Tools

SAMEgen is a small test generator for the National Weather Service’s Specific Area Message Encoding (SAME) coding and may find use in both development of decoding circuitry and in testing SAME-enabled receivers. SAME is used by the NOAA Weather Radio (NWR) broadcasts and the Emergency Alert System (EAS) to disseminate weather watches, warnings, and other emergency alerts to the public. Typical alerts might be tornado, hurricane, or severe storm watches or warnings.

Specific Area Message Encoding Test Generator

The SAMEgen was designed and built due to a need to test development circuits used to detect and decode the SAME messages. As one can imagine, testing a circuit or a receiver by waiting for a weekly NWR test or actual bad weather conditions is not the way to go. A properly encoded test signal, available on push button demand, is indispensable to development and test work.

The system based on AVR microcontroller, ATtiny45. In the firmware, timing for the generation of the signal is controlled by an internal timer with interrupts. The interrupts and several software counters allow phase coherent generation of the specified code. The signal is an Audio Frequency Shift Keying signal using 8-bit bytes and no start or stop bits, said Don L. Jackson, the project designer.