espressif: Correct comments on IncrementalEncoder

Author: jepler

ports/espressif/common-hal/rotaryio/IncrementalEncoder.c

@@ -35,15 +35,24 @@ void common_hal_rotaryio_incrementalencoder_construct(rotaryio_incrementalencode
     claim_pin(pin_a);
     claim_pin(pin_b);
 
+    // This configuration counts on all edges of the quadrature signal: Channel 0
+    // counts on rising and falling edges of channel A, with the direction set by the
+    // polarity of channel B. Channel 1 does likewise, counting edges of channel B according
+    // to the polarity of channel A. A little pencil work suffices to show that this
+    // counts correctly on all 8 correct quadrature state transitions.
+    //
+    // These routines also implicitly configure the weak internal pull-ups, as expected
+    // in CircuitPython.
+
     // Prepare configuration for the PCNT unit
     pcnt_config_t pcnt_config_channel_0 = {
         // Set PCNT input signal and control GPIOs
         .pulse_gpio_num = pin_a->number,
         .ctrl_gpio_num = pin_b->number,
         .channel = PCNT_CHANNEL_0,
         // What to do on the positive / negative edge of pulse input?
-        .pos_mode = PCNT_COUNT_DEC,      // Count up on the positive edge
-        .neg_mode = PCNT_COUNT_INC,      // Keep the counter value on the negative edge
+        .pos_mode = PCNT_COUNT_DEC,      // Count down on the positive edge
+        .neg_mode = PCNT_COUNT_INC,      // Count up on negative edge
         // What to do when control input is low or high?
         .lctrl_mode = PCNT_MODE_REVERSE, // Reverse counting direction if low
         .hctrl_mode = PCNT_MODE_KEEP,    // Keep the primary counter mode if high
@@ -61,8 +70,8 @@ void common_hal_rotaryio_incrementalencoder_construct(rotaryio_incrementalencode
         .ctrl_gpio_num = pin_a->number,
         .channel = PCNT_CHANNEL_1,
         // What to do on the positive / negative edge of pulse input?
-        .pos_mode = PCNT_COUNT_DEC,      // Count up on the positive edge
-        .neg_mode = PCNT_COUNT_INC,      // Keep the counter value on the negative edge
+        .pos_mode = PCNT_COUNT_DEC,      // Count down on the positive edge
+        .neg_mode = PCNT_COUNT_INC,      // Count up on negative edge
         // What to do when control input is low or high?
         .lctrl_mode = PCNT_MODE_KEEP,        // Keep the primary counter mode if low
         .hctrl_mode = PCNT_MODE_REVERSE,     // Reverse counting direction if high