Added blurb about do_waveform.

diff --git a/demo/README b/demo/README
index f709fb94f4973a16e6c103230d480dff86d3b7f8..92381867bb26a7af49c2d4cb3edc7788a6bb3170 100644 (file)
--- a/demo/README
+++ b/demo/README
@@ -64,6 +64,28 @@ dio:
        an input.  Once the channel's direction has been configured,
        you can read/write to it with the inp/outp demo programs.
 
+do_waveform:
+       Requirements: NI M-Series board.
+       This demo uses the digital io subdevice with an
+       asynchronous command to generate waveforms.  The
+       waveforms in this example are square waves with
+       varying periods depending on the digital output
+       channel.  Channel N outputs a square wave with
+       period 2*(N+1) clocks. The command line argument chooses the
+       clock signal for updating the outputs.  As a suggestion,
+       you might use the output of one of the general
+       purpose counters for a clock (the default clock
+       source is the output of general purpose counter 0),
+       and run the gpct_pulse_generator demo to start the counter
+       generating pulses on its output.
+
+       Note, you must configure at least one of the digital channels as
+       an output (for example by running the dio demo program)
+       before running this program. You must also pass the dio
+       subdevice file using the -f option, since the default write
+       subdevice for the m-series boards is the analog output.  For
+       example, "dio_waveform -f /dev/comedi0_sub2".
+
 eeprom_dump:
        Dumps the EEPROM of a card, if it has one.  Useful for debugging
        devices/drivers.