|PSK31 Audio Beacon|
App #1: Tone Gen
SX28 TONE GENERATOR
Although the PSK31 Beacon
board comes with a pre-programmed SX chip containing the Beacon program
and your custom text beacon string, you can burn a new program into it
that we’ll develop right here. Don’t worry, you can always just load
up the original Beacon code in the editor and program it into the chip
The simple Tone Generator
program that we’ll create for the Beacon board uses a look-up-table (LUT)
technique for putting sine wave values out to the R-2R D/A converter
hanging off port B of the SX chip. See the PSK31 Beacon schematic
page for detail on how this D/A works. This continuous stream of sine wave
values, each separated by a short delay, will form a 0-to-5V sine wave
running at 1 kHz into the LM386 audio amp.
You could either enter the
short assembly language source code program by hand as listed below, or
you could download the source file and load it up into the SXkey
editor. Selecting the Assemble menu item should produce an error-free
assembly and you can program your SX chip as described previously.
When you run the ToneGen program, you should hear a strong 1 kHz tone coming from the speaker hanging off the LM386 output. At this point you could change the value of thedouble-byte variable FREQ_HI and FREQ_LO and see how it changes the tone when the program is assembled and run again. The FREQ variable determines how long of a delay is inserted between each sine wave sample that is put out to the D/A … hence the frequency of the waveform is changed.
Coming soon ...
Yes indeed, there's lots of
fun still planned for this base project. Please
be sure to regularly check back here for a growing amount of detail and
additional applications coming your way.
Page last modified:
November 28, 2001