RGBMatrix: Additional tile tweaks

 * Introduce explicit serpentine: bool argument instead of using negative
   numbers (thanks, ghost of @tannewt sitting on one shoulder)
 * Fix several calculations of height

Testing performed (matrixportal):
 * set up a serpentine 64x64 virtual display with 2 64x32 tiles
 * tried all 4 rotations
 * looked at output of REPL

2 files changed, 9 insertions, 10 deletions

diff --git a/shared-bindings/rgbmatrix/RGBMatrix.c b/shared-bindings/rgbmatrix/RGBMatrix.c
index ad693066c..7218b2a9e 100644
--- a/shared-bindings/rgbmatrix/RGBMatrix.c
+++ b/shared-bindings/rgbmatrix/RGBMatrix.c
@@ -24,8 +24,6 @@
  * THE SOFTWARE.
  */
 
-#include <stdlib.h>
-
 #include "py/obj.h"
 #include "py/objproperty.h"
 #include "py/runtime.h"
@@ -216,18 +214,19 @@ STATIC mp_obj_t rgbmatrix_rgbmatrix_make_new(const mp_obj_type_t *type, size_t n
 
     int tile = args[ARG_tile].u_int;
 
+    if (tile < 0) {
+        mp_raise_ValueError_varg(
+            translate("tile must be greater than or equal to zero"));
+    }
+
     if (args[ARG_height].u_int != 0) {
-        int computed_height = (rgb_count / 3) << (addr_count) * abs(tile);
+        int computed_height = (rgb_count / 3) * (1 << (addr_count)) * tile;
         if (computed_height != args[ARG_height].u_int) {
             mp_raise_ValueError_varg(
                 translate("%d address pins, %d rgb pins and %d tiles indicate a height of %d, not %d"), addr_count, rgb_count, tile, computed_height, args[ARG_height].u_int);
         }
     }
 
-    if (args[ARG_serpentine].u_bool) {
-        tile = -tile;
-    }
-
     if (args[ARG_width].u_int <= 0) {
         mp_raise_ValueError(translate("width must be greater than zero"));
     }
@@ -237,7 +236,7 @@ STATIC mp_obj_t rgbmatrix_rgbmatrix_make_new(const mp_obj_type_t *type, size_t n
     mp_obj_t framebuffer = args[ARG_framebuffer].u_obj;
     if (framebuffer == mp_const_none) {
         int width = args[ARG_width].u_int;
-        int bufsize = 2 * width * rgb_count / 3 * (1 << addr_count);
+        int bufsize = 2 * width * rgb_count / 3 * (1 << addr_count) * tile;
         framebuffer = mp_obj_new_bytearray_of_zeros(bufsize);
     }
 
@@ -248,7 +247,7 @@ STATIC mp_obj_t rgbmatrix_rgbmatrix_make_new(const mp_obj_type_t *type, size_t n
         addr_count, addr_pins,
         clock_pin, latch_pin, output_enable_pin,
         args[ARG_doublebuffer].u_bool,
-        framebuffer, tile, NULL);
+        framebuffer, tile, args[ARG_serpentine].u_bool, NULL);
 
     claim_and_never_reset_pins(args[ARG_rgb_list].u_obj);
     claim_and_never_reset_pins(args[ARG_addr_list].u_obj);
diff --git a/shared-bindings/rgbmatrix/RGBMatrix.h b/shared-bindings/rgbmatrix/RGBMatrix.h
index 3e8a4db5f..4eb3c04b2 100644
--- a/shared-bindings/rgbmatrix/RGBMatrix.h
+++ b/shared-bindings/rgbmatrix/RGBMatrix.h
@@ -31,7 +31,7 @@
 
 extern const mp_obj_type_t rgbmatrix_RGBMatrix_type;
 
-void common_hal_rgbmatrix_rgbmatrix_construct(rgbmatrix_rgbmatrix_obj_t* self, int width, int bit_depth, uint8_t rgb_count, uint8_t* rgb_pins, uint8_t addr_count, uint8_t* addr_pins, uint8_t clock_pin, uint8_t latch_pin, uint8_t oe_pin, bool doublebuffer, mp_obj_t framebuffer, int8_t tile, void* timer);
+void common_hal_rgbmatrix_rgbmatrix_construct(rgbmatrix_rgbmatrix_obj_t* self, int width, int bit_depth, uint8_t rgb_count, uint8_t* rgb_pins, uint8_t addr_count, uint8_t* addr_pins, uint8_t clock_pin, uint8_t latch_pin, uint8_t oe_pin, bool doublebuffer, mp_obj_t framebuffer, int8_t tile, bool serpentine, void* timer);
 void common_hal_rgbmatrix_rgbmatrix_deinit(rgbmatrix_rgbmatrix_obj_t*);
 void rgbmatrix_rgbmatrix_collect_ptrs(rgbmatrix_rgbmatrix_obj_t*);
 void common_hal_rgbmatrix_rgbmatrix_reconstruct(rgbmatrix_rgbmatrix_obj_t* self, mp_obj_t framebuffer);