rgbmatrix: Check that the number of rgb pins is supported.

Having zero RGB pins may not have been caught, nor having a non-multiple-of-6
value.  Generally, users will only have 6 RGB pins unless they are driving
multiple matrices in parallel.  No existing breakouts exist to do this, and
there are probably not any efficient pinouts to be had anyway.

Author: jepler

locale/circuitpython.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-09-29 11:11+0530\n"
+"POT-Creation-Date: 2020-09-29 19:54-0500\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <[email protected]>\n"
@@ -1662,6 +1662,10 @@ msgid ""
 "exit safe mode.\n"
 msgstr ""
 
+#: shared-bindings/rgbmatrix/RGBMatrix.c
+msgid "The length of rgb_pins must be 6, 12, 18, 24, or 30"
+msgstr ""
+
 #: supervisor/shared/safe_mode.c
 msgid ""
 "The microcontroller's power dipped. Make sure your power supply provides\n"
@@ -3516,6 +3520,10 @@ msgstr ""
 msgid "watchdog timeout must be greater than 0"
 msgstr ""
 
+#: shared-bindings/rgbmatrix/RGBMatrix.c
+msgid "width must be greater than zero"
+msgstr ""
+
 #: shared-bindings/_bleio/Adapter.c
 msgid "window must be <= interval"
 msgstr ""

shared-bindings/rgbmatrix/RGBMatrix.c

@@ -73,6 +73,10 @@ STATIC void preflight_pins_or_throw(uint8_t clock_pin, uint8_t *rgb_pins, uint8_
     uint32_t port = clock_pin / 32;
     uint32_t bit_mask = 1 << (clock_pin % 32);
 
+    if (rgb_pin_count <= 0 || rgb_pin_count % 6 != 0 || rgb_pin_count > 30) {
+        mp_raise_ValueError_varg(translate("The length of rgb_pins must be 6, 12, 18, 24, or 30"));
+    }
+
     for (uint8_t i = 0; i < rgb_pin_count; i++) {
         uint32_t pin_port = rgb_pins[i] / 32;