Fix various issues with NintendoSwitchBackend

NintendoSwitchBackend had several issues. Firstly, I messed up the
descriptor, which was why this comms backend didn't work on PC.
Secondly, because the Nintendo Switch apparently applies a deadzone and
scaling to GameCube controller analog stick inputs, it was necessary to
reverse engineer this scaling and replicate it in NintendoSwitchBackend
so that we scale the inputs before sending them to the console, in the
same way that the Switch would scale them after receiving them. Until
now I have been using a naive multiplication which was not close enough
to the actual formula to prevent input issues manifesting when using the
Ultimate mode. Thanks to Zeronia, we have much more data now and I have
been able to reverse engineer the scaling formula to get one that
matches almost exactly. The only remaining considerations are that the
GameCube controller C-Stick is apparently scaled differently to the left
analog stick, and that I have only implemented a basic square deadzone
rather than a circular deadzone. It is yet to be seen whether these
things will cause any input inconsistencies in existing controller
modes.

Author: JonnyHaystack

.github/workflows/build-device-config.yml

@@ -34,7 +34,7 @@ jobs:
       BIN_EXT: ${{ matrix.bin_ext }}
     strategy:
       fail-fast: false
-      matrix: 
+      matrix:
         include: ${{ fromJson(needs.metadata.outputs.meta_json).build }}
 
     steps:

HAL/pico/include/comms/NintendoSwitchBackend.hpp

@@ -55,7 +55,7 @@ class NintendoSwitchBackend : public CommunicationBackend {
 
   protected:
     static const uint8_t _report_id = 0;
-    static uint8_t _descriptor[];
+    static const uint8_t _descriptor[];
 
     switch_gamepad_report_t _report;
 

HAL/pico/src/comms/NintendoSwitchBackend.cpp

@@ -2,6 +2,7 @@
 
 #include "core/CommunicationBackend.hpp"
 #include "core/state.hpp"
+#include "util/analog_filters.hpp"
 
 #include <Adafruit_TinyUSB.h>
 #include <TUCompositeHID.hpp>
@@ -61,7 +62,10 @@
 
 // clang-format on
 
-uint8_t NintendoSwitchBackend::_descriptor[] = { HID_REPORT_DESC() };
+const uint8_t NintendoSwitchBackend::_descriptor[] = { HID_REPORT_DESC() };
+
+const uint8_t DEADZONE = 11;
+const int RADIUS = 256;
 
 NintendoSwitchBackend::NintendoSwitchBackend(
     InputState &inputs,
@@ -139,10 +143,10 @@ void NintendoSwitchBackend::SendReport() {
     _report.home = _outputs.home;
 
     // Analog outputs
-    _report.lx = (_outputs.leftStickX - 128) * 1.25 + 128;
-    _report.ly = 255 - ((_outputs.leftStickY - 128) * 1.25 + 128);
-    _report.rx = (_outputs.rightStickX - 128) * 1.25 + 128;
-    _report.ry = 255 - ((_outputs.rightStickY - 128) * 1.25 + 128);
+    _report.lx = apply_radius(apply_deadzone(_outputs.leftStickX, DEADZONE, true), RADIUS);
+    _report.ly = 255 - apply_radius(apply_deadzone(_outputs.leftStickY, DEADZONE, true), RADIUS);
+    _report.rx = apply_radius(apply_deadzone(_outputs.rightStickX, DEADZONE, true), RADIUS);
+    _report.ry = 255 - apply_radius(apply_deadzone(_outputs.rightStickY, DEADZONE, true), RADIUS);
 
     // D-pad Hat Switch
     _report.hat =

include/util/analog_filters.hpp

@@ -0,0 +1,9 @@
+#ifndef _UTIL_ANALOG_FILTERS_HPP
+#define _UTIL_ANALOG_FILTERS_HPP
+
+#include "stdlib.hpp"
+
+uint8_t apply_deadzone(uint8_t value, uint8_t deadzone, bool scale);
+uint8_t apply_radius(uint8_t value, int radius);
+
+#endif

lib/TUCompositeHID/include/TUCompositeHID.hpp

@@ -7,7 +7,7 @@
 namespace TUCompositeHID {
     extern Adafruit_USBD_HID _usb_hid;
 
-    bool addDescriptor(uint8_t *descriptor, size_t descriptor_len);
+    bool addDescriptor(const uint8_t *descriptor, size_t descriptor_len);
 }
 
 #endif

lib/TUCompositeHID/include/TUGamepad.hpp

@@ -67,7 +67,7 @@ class TUGamepad {
 
   protected:
     static const uint8_t _report_id = 1;
-    static uint8_t _descriptor[];
+    static const uint8_t _descriptor[];
 
     gamepad_report_t _report;
 

lib/TUCompositeHID/include/TUKeyboard.hpp

@@ -20,7 +20,7 @@ class TUKeyboard {
 
   private:
     static const uint8_t _report_id = 2;
-    static uint8_t _descriptor[];
+    static const uint8_t _descriptor[];
 
     hid_keyboard_report_t _report;
 };

lib/TUCompositeHID/src/TUCompositeHID.cpp

@@ -16,7 +16,7 @@ namespace TUCompositeHID {
         false
     );
 
-    bool addDescriptor(uint8_t *descriptor, size_t descriptor_len) {
+    bool addDescriptor(const uint8_t *descriptor, size_t descriptor_len) {
         if (_current_descriptor_len + descriptor_len > HID_DESCRIPTOR_BUFSIZE) {
             return false;
         }

lib/TUCompositeHID/src/TUGamepad.cpp

@@ -71,7 +71,7 @@ SOFTWARE.
 
 // clang-format on
 
-uint8_t TUGamepad::_descriptor[] = { HID_REPORT_DESC(HID_REPORT_ID(_report_id)) };
+const uint8_t TUGamepad::_descriptor[] = { HID_REPORT_DESC(HID_REPORT_ID(_report_id)) };
 
 TUGamepad::TUGamepad() {}
 

lib/TUCompositeHID/src/TUKeyboard.cpp

@@ -3,7 +3,9 @@
 #include <Adafruit_TinyUSB.h>
 #include <TUCompositeHID.hpp>
 
-uint8_t TUKeyboard::_descriptor[] = { TUD_HID_REPORT_DESC_KEYBOARD(HID_REPORT_ID(_report_id)) };
+// clang-format off
+const uint8_t TUKeyboard::_descriptor[] = { TUD_HID_REPORT_DESC_KEYBOARD(HID_REPORT_ID(_report_id)) };
+// clang-format on
 
 #define MODIFIER_MASK(mod_kc) (1 << (mod_kc & 0x0F))