Fix incorrect C2 designator for audio input section (should be C1).

Build/NucleoTNC.ipynb

@@ -211,13 +211,13 @@
     "\n",
     "There are a number of components in this subsection:\n",
     "\n",
-    " * C2 - 1uF DC blocking capacitor.*\n",
+    " * C1 - 1uF DC blocking capacitor.*\n",
-    " * R1 - 10K DC-offset resistor, along with C2 forms a 15Hz high-pass filter.\n",
+    " * R1 - 10K DC-offset resistor, along with C1 forms a 15Hz high-pass filter.\n",
     " * D1, D2 - voltage limiter.\n",
     " * U1C - audio buffer.\n",
     " * R7, R10, R14, C4, C6, C8, and U1D - 3-pole active Bessel anti-aliasing filter.\n",
     " \n",
-    "C2 was changed in 2021 to a 1uF to improve the low frequency response needed for 9600 baud.\n",
+    "C1 was changed in 2021 to a 1uF to improve the low frequency response needed for 9600 baud.\n",
     "\n",
     "The quad op amp U1 is shared across the Audio Input and Audio Output sections.\n",
     " \n",
@@ -311,7 +311,7 @@
     "\n",
     "It might be worthwhile to buy an extra one of each of the passive components in case one is lost or a lead is accidentally cut too short.\n",
     "\n",
-    "*Note: C2 was changed from a 220nF capacitor to a 1uF capacitor in early 2021.*\n",
+    "*Note: C1 was changed from a 220nF capacitor to a 1uF capacitor in early 2021.*\n",
     "\n",
     "### Substitutions\n",
     "\n",
@@ -578,7 +578,7 @@
     " * Connect one diode from *a49* to the lower ground rail. The cathode band should be nearest *a49*.\n",
     " * Connect one diode from *j49* to the upper power rail.  The cathode bnad should be neares the power rail.\n",
     " * Connect a jumper wire across the *e49-f49* gap.\n",
-    " * Connect the 1uF capacitor, C2, from *e50* to *g49*.\n",
+    " * Connect the 1uF capacitor, C1, from *e50* to *g49*.\n",
     " * Connect the 10kΩ resistor from *h46* to *h49*.\n",
     " * Connect a wire from *i49* to *i36*.\n",
     " * Connect a short jumper from *g37* to *g38*, tying VinA- to VoutA\n",