Updated README.md

zarath · Sep 19, 2023 · 32bc04e · 32bc04e
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diff --git a/Oscilloscope.png b/Oscilloscope.png
diff --git a/README.md b/README.md
@@ -5,9 +5,18 @@ An embedded rust project to generate
 [CTCSS](https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System)-Tones
 via [PDM](https://en.wikipedia.org/wiki/Pulse-density_modulation) on a cheap
 [RP2040](https://en.wikipedia.org/wiki/RP2040) board.
+Due to PDM (aka Delta-Modulation) a simple rc-filter is sufficient for
+DA-conversation.
+(eg. 100Ω/3.3µF if not using 1750Hz option or 100Ω/470nF otherwise)
+Prefer tantalum caps for better switching supression.
 
 ![prototype](Prototype.jpg "Prototype attached to 23cm tranciever")
 
+Waveform Example
+----------------
+
+![waveform](Oscilloscope.png "Waveform example on oscilloscope")
+
 Schematics
 ----------
 
@@ -21,4 +30,6 @@ Usage
 
 * Use rotary encoder to select wanted frequency.
 * Press button short for on/off toggling.
-* Press long to store current setting.
+* Press long to store current setting.
+* With 1750Hz call-tone option on this frequency short button push just emmits
+  a one second sine pulse and is quiet otherwise.