From fc86475de58581bd48d67ecc733377a5ed713367 Mon Sep 17 00:00:00 2001
From: Jeff Epler <jepler@gmail.com>
Date: Sun, 4 Apr 2021 13:48:47 -0500
Subject: [PATCH] IncrementalEncoder: support swapped pins

Closes: #4422
---
 .../common-hal/rotaryio/IncrementalEncoder.c      | 15 +++++++++++----
 .../common-hal/rotaryio/IncrementalEncoder.h      |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.c b/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.c
index 5c61e0915c..faef077972 100644
--- a/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.c
+++ b/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.c
@@ -60,10 +60,17 @@ STATIC void incrementalencoder_interrupt_handler(void *self_in);
 void common_hal_rotaryio_incrementalencoder_construct(rotaryio_incrementalencoder_obj_t *self,
     const mcu_pin_obj_t *pin_a, const mcu_pin_obj_t *pin_b) {
     mp_obj_t pins[] = {MP_OBJ_FROM_PTR(pin_a), MP_OBJ_FROM_PTR(pin_b)};
+    bool swap = false;
     if (!common_hal_rp2pio_pins_are_sequential(2, pins)) {
-        mp_raise_RuntimeError(translate("Pins must be sequential"));
+        pins[0] = MP_OBJ_FROM_PTR(pin_b);
+        pins[1] = MP_OBJ_FROM_PTR(pin_a);
+        swap = true;
+        if (!common_hal_rp2pio_pins_are_sequential(2, pins)) {
+            mp_raise_RuntimeError(translate("Pins must be sequential"));
+        }
     }
 
+    self->swap = swap;
     self->position = 0;
     self->quarter_count = 0;
 
@@ -72,7 +79,7 @@ void common_hal_rotaryio_incrementalencoder_construct(rotaryio_incrementalencode
         1000000,
         encoder_init, MP_ARRAY_SIZE(encoder_init), // init
         NULL, 0, 0, 0, // out pin
-        pin_a, 2, // in pins
+        pins[0], 2, // in pins
         3, 0, // in pulls
         NULL, 0, 0, 0x1f, // set pins
         NULL, 0, 0, 0x1f, // sideset pins
@@ -106,12 +113,12 @@ void common_hal_rotaryio_incrementalencoder_deinit(rotaryio_incrementalencoder_o
 }
 
 mp_int_t common_hal_rotaryio_incrementalencoder_get_position(rotaryio_incrementalencoder_obj_t *self) {
-    return self->position;
+    return self->swap ? -self->position : self->position;
 }
 
 void common_hal_rotaryio_incrementalencoder_set_position(rotaryio_incrementalencoder_obj_t *self,
     mp_int_t new_position) {
-    self->position = new_position;
+    self->position = self->swap ? -new_position : new_position;
 }
 
 STATIC void incrementalencoder_interrupt_handler(void *self_in) {
diff --git a/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.h b/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.h
index 83fe97d316..d74c21035e 100644
--- a/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.h
+++ b/ports/raspberrypi/common-hal/rotaryio/IncrementalEncoder.h
@@ -37,4 +37,5 @@ typedef struct {
     uint8_t last_state : 4;   // <old A><old B><new A><new B>
     int8_t quarter_count : 4; // count intermediate transitions between detents
     mp_int_t position;
+    bool swap;
 } rotaryio_incrementalencoder_obj_t;