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Created September 19, 2019 21:22
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Patch teensyduino for NKRO on Teensy 3.2

Patching teensyduino to support NKRO for Teensy 3.2

  1. Install Arduino IDE

  2. Install teensyduino using its installer

  3. Run the following:

    cd /Applications/Arduino.app/Contents/Java/hardware/teensy
    git init
    git add -A
    git commit -m 'Initial commit'
    git apply 0001-NKRO.patch
    
  4. Example script:

    void setup() { }
    
    void loop() {
       Nkro.set_key(KEY_A);
       Nkro.send_nkro_now();
       delay(1000);
       Nkro.reset_keys();
       delay(1000);
    }

0001-NKRO.patch

From 1ba54c9a4c9ecf3565eb3a5a88a635365396d34f Mon Sep 17 00:00:00 2001
From: Ethan Smith <[email protected]>
Date: Thu, 19 Sep 2019 12:51:58 -0400
Subject: [PATCH] NKRO

---
 avr/cores/teensy3/WProgram.h   |   1 +
 avr/cores/teensy3/usb_desc.c   |  70 ++++++++++++++++-
 avr/cores/teensy3/usb_desc.h   |  49 +++++++++---
 avr/cores/teensy3/usb_dev.h    |   7 ++
 avr/cores/teensy3/usb_inst.cpp |   3 +
 avr/cores/teensy3/usb_nkro.c   | 132 +++++++++++++++++++++++++++++++++
 avr/cores/teensy3/usb_nkro.h   |  43 +++++++++++
 avr/cores/teensy3/usb_undef.h  |  19 ++++-
 8 files changed, 312 insertions(+), 12 deletions(-)
 create mode 100644 avr/cores/teensy3/usb_nkro.c
 create mode 100644 avr/cores/teensy3/usb_nkro.h

diff --git a/avr/cores/teensy3/WProgram.h b/avr/cores/teensy3/WProgram.h
index e67de41..6eed438 100644
--- a/avr/cores/teensy3/WProgram.h
+++ b/avr/cores/teensy3/WProgram.h
@@ -54,6 +54,7 @@
 #include "usb_serial.h"
 #include "usb_seremu.h"
 #include "usb_keyboard.h"
+#include "usb_nkro.h"
 #include "usb_mouse.h"
 #include "usb_joystick.h"
 #include "usb_midi.h"
diff --git a/avr/cores/teensy3/usb_desc.c b/avr/cores/teensy3/usb_desc.c
index 182ae6d..fe560c3 100644
--- a/avr/cores/teensy3/usb_desc.c
+++ b/avr/cores/teensy3/usb_desc.c
@@ -188,6 +188,33 @@ static uint8_t keymedia_report_desc[] = {
 };
 #endif
 
+#ifdef NKRO_INTERFACE
+static uint8_t nkro_hid_report_desc[] = {
+        0x05, 0x01, // Usage Page (Generic Desktop),
+        0x09, 0x06, // Usage (Keyboard),
+        0xA1, 0x01, // Collection (Application),
+        // bitmap of modifiers
+        0x75, 0x01, // Report Size (1),
+        0x95, 0x08, // Report Count (8),
+        0x05, 0x07, // Usage Page (Key Codes),
+        0x19, 0xE0, // Usage Minimum (224),
+        0x29, 0xE7, // Usage Maximum (231),
+        0x15, 0x00, // Logical Minimum (0),
+        0x25, 0x01, // Logical Maximum (1),
+        0x81, 0x02, // Input (Data, Variable, Absolute), ;Modifier byte
+        // bitmap of keys
+        0x95, NKRO_REPORT_KEYS*8, // Report Count (),
+        0x75, 0x01, // Report Size (1),
+        0x15, 0x00, // Logical Minimum (0),
+        0x25, 0x01, // Logical Maximum(1),
+        0x05, 0x07, // Usage Page (Key Codes),
+        0x19, 0x00, // Usage Minimum (0),
+        0x29, NKRO_REPORT_KEYS*8-1, // Usage Maximum (),
+        0x81, 0x02, // Input (Data, Variable, Absolute),
+        0xc0 // End Collection
+};
+#endif
+
 #ifdef MOUSE_INTERFACE
 // Mouse Protocol 1, HID 1.11 spec, Appendix B, page 59-60, with wheel extension
 static uint8_t mouse_report_desc[] = {
@@ -542,7 +569,15 @@ static uint8_t flightsim_report_desc[] = {
 #define JOYSTICK_INTERFACE_DESC_SIZE  0
 #endif
 
-#define MTP_INTERFACE_DESC_POS     JOYSTICK_INTERFACE_DESC_POS+JOYSTICK_INTERFACE_DESC_SIZE
+#define NKRO_INTERFACE_DESC_POS    JOYSTICK_INTERFACE_DESC_POS+JOYSTICK_INTERFACE_DESC_SIZE
+#ifdef NKRO_INTERFACE
+#define NKRO_INTERFACE_DESC_SIZE 9+9+7
+#define NKRO_DESC_OFFSET NKRO_INTERFACE_DESC_POS+9
+#else
+#define NKRO_INTERFACE_DESC_SIZE 0
+#endif
+
+#define MTP_INTERFACE_DESC_POS     NKRO_INTERFACE_DESC_POS+NKRO_INTERFACE_DESC_SIZE
 #ifdef  MTP_INTERFACE
 #define MTP_INTERFACE_DESC_SIZE    9+7+7+7
 #else
@@ -1091,6 +1126,35 @@ static uint8_t config_descriptor[CONFIG_DESC_SIZE] = {
         JOYSTICK_INTERVAL,                      // bInterval
 #endif // JOYSTICK_INTERFACE
 
+#ifdef NKRO_INTERFACE
+        // interface descriptor, USB spec 9.6.5, page 267-269, Table 9-12
+        9, // bLength
+        4, // bDescriptorType
+        NKRO_INTERFACE, // bInterfaceNumber
+        0, // bAlternateSetting
+        1, // bNumEndpoints
+        0x03, // bInterfaceClass (0x03 = HID)
+        0x00, // bInterfaceSubClass (0x01 = Boot)
+        0x00, // bInterfaceProtocol (0x01 = Keyboard)
+        0, // iInterface
+        // HID interface descriptor, HID 1.11 spec, section 6.2.1
+        9, // bLength
+        0x21, // bDescriptorType
+        0x11, 0x01, // bcdHID
+        0, // bCountryCode
+        1, // bNumDescriptors
+        0x22, // bDescriptorType
+        LSB(sizeof(nkro_hid_report_desc)), // wDescriptorLength
+        MSB(sizeof(nkro_hid_report_desc)),
+        // endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
+        7, // bLength
+        5, // bDescriptorType
+        NKRO_ENDPOINT | 0x80, // bEndpointAddress
+        0x03, // bmAttributes (0x03=intr)
+        NKRO_SIZE, 0, // wMaxPacketSize
+        NKRO_INTERVAL, // bInterval
+#endif // NKRO_INTERFACE
+
 #ifdef MTP_INTERFACE
         // interface descriptor, USB spec 9.6.5, page 267-269, Table 9-12
         9,                                      // bLength
@@ -1517,6 +1581,10 @@ const usb_descriptor_list_t usb_descriptor_list[] = {
         {0x2200, JOYSTICK_INTERFACE, joystick_report_desc, sizeof(joystick_report_desc)},
         {0x2100, JOYSTICK_INTERFACE, config_descriptor+JOYSTICK_HID_DESC_OFFSET, 9},
 #endif
+#ifdef NKRO_INTERFACE
+        {0x2200, NKRO_INTERFACE, nkro_hid_report_desc, sizeof(nkro_hid_report_desc)},
+        {0x2100, NKRO_INTERFACE, config_descriptor+NKRO_DESC_OFFSET, 9},
+#endif
 #ifdef RAWHID_INTERFACE
   {0x2200, RAWHID_INTERFACE, rawhid_report_desc, sizeof(rawhid_report_desc)},
   {0x2100, RAWHID_INTERFACE, config_descriptor+RAWHID_HID_DESC_OFFSET, 9},
diff --git a/avr/cores/teensy3/usb_desc.h b/avr/cores/teensy3/usb_desc.h
index 95de05e..abc8bbd 100644
--- a/avr/cores/teensy3/usb_desc.h
+++ b/avr/cores/teensy3/usb_desc.h
@@ -148,9 +148,9 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define PRODUCT_NAME    {'K','e','y','b','o','a','r','d'}
   #define PRODUCT_NAME_LEN   8
   #define EP0_SIZE     64
-  #define NUM_ENDPOINTS         4
+  #define NUM_ENDPOINTS         5
   #define NUM_USB_BUFFERS 14
-  #define NUM_INTERFACE      3
+  #define NUM_INTERFACE      4
   #define SEREMU_INTERFACE      1  // Serial emulation
   #define SEREMU_TX_ENDPOINT    1
   #define SEREMU_TX_SIZE        64
@@ -166,6 +166,11 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define KEYMEDIA_ENDPOINT     4
   #define KEYMEDIA_SIZE         8
   #define KEYMEDIA_INTERVAL     4
+  #define NKRO_INTERFACE        6  // N-key rollover kbd
+  #define NKRO_ENDPOINT         5
+  #define NKRO_SIZE             32
+  #define NKRO_REPORT_KEYS      ( NKRO_SIZE - 1 )
+  #define NKRO_INTERVAL         1
   #define ENDPOINT1_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG   ENDPOINT_RECEIVE_ONLY
   #define ENDPOINT3_CONFIG   ENDPOINT_TRANSIMIT_ONLY
@@ -181,9 +186,9 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define PRODUCT_NAME    {'K','e','y','b','o','a','r','d','/','M','o','u','s','e','/','J','o','y','s','t','i','c','k'}
   #define PRODUCT_NAME_LEN   23
   #define EP0_SIZE     64
-  #define NUM_ENDPOINTS         6
+  #define NUM_ENDPOINTS         7
   #define NUM_USB_BUFFERS 24
-  #define NUM_INTERFACE      5
+  #define NUM_INTERFACE      6
   #define SEREMU_INTERFACE      2  // Serial emulation
   #define SEREMU_TX_ENDPOINT    1
   #define SEREMU_TX_SIZE        64
@@ -207,12 +212,18 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define JOYSTICK_ENDPOINT     4
   #define JOYSTICK_SIZE         12 //  12 = normal, 64 = extreme joystick
   #define JOYSTICK_INTERVAL     2
+  #define NKRO_INTERFACE        5  // N-key rollover kbd
+  #define NKRO_ENDPOINT         7
+  #define NKRO_SIZE             32
+  #define NKRO_REPORT_KEYS      ( NKRO_SIZE - 1 )
+  #define NKRO_INTERVAL         1
   #define ENDPOINT1_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG   ENDPOINT_RECEIVE_ONLY
   #define ENDPOINT3_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT4_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT5_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT6_CONFIG   ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT7_CONFIG   ENDPOINT_TRANSIMIT_ONLY
 
 #elif defined(USB_SERIAL_HID)
   #define VENDOR_ID    0x16C0
@@ -225,9 +236,9 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define PRODUCT_NAME    {'S','e','r','i','a','l','/','K','e','y','b','o','a','r','d','/','M','o','u','s','e','/','J','o','y','s','t','i','c','k'}
   #define PRODUCT_NAME_LEN   30
   #define EP0_SIZE     64
-  #define NUM_ENDPOINTS      7
+  #define NUM_ENDPOINTS      8
   #define NUM_USB_BUFFERS 30
-  #define NUM_INTERFACE      6
+  #define NUM_INTERFACE      7
   #define CDC_IAD_DESCRIPTOR 1
   #define CDC_STATUS_INTERFACE  0
   #define CDC_DATA_INTERFACE 1  // Serial
@@ -253,6 +264,11 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define JOYSTICK_ENDPOINT     6
   #define JOYSTICK_SIZE         12 //  12 = normal, 64 = extreme joystick
   #define JOYSTICK_INTERVAL     1
+  #define NKRO_INTERFACE        6  // N-key rollover kbd
+  #define NKRO_ENDPOINT         8
+  #define NKRO_SIZE             32
+  #define NKRO_REPORT_KEYS      ( NKRO_SIZE - 1 )
+  #define NKRO_INTERVAL         1
   #define ENDPOINT1_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT3_CONFIG   ENDPOINT_RECEIVE_ONLY
@@ -260,6 +276,7 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define ENDPOINT5_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT6_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT7_CONFIG   ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT8_CONFIG   ENDPOINT_TRANSIMIT_ONLY
 
 #elif defined(USB_TOUCHSCREEN)
   #define VENDOR_ID    0x16C0
@@ -269,9 +286,9 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define PRODUCT_NAME    {'K','e','y','b','o','a','r','d','/','T','o','u','c','h','s','c','r','e','e','n'}
   #define PRODUCT_NAME_LEN   20
   #define EP0_SIZE     64
-  #define NUM_ENDPOINTS         5
+  #define NUM_ENDPOINTS         6
   #define NUM_USB_BUFFERS 15
-  #define NUM_INTERFACE      4
+  #define NUM_INTERFACE      5
   #define SEREMU_INTERFACE      1  // Serial emulation
   #define SEREMU_TX_ENDPOINT    1
   #define SEREMU_TX_SIZE        64
@@ -291,11 +308,17 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define MULTITOUCH_ENDPOINT   5
   #define MULTITOUCH_SIZE       8
   #define MULTITOUCH_FINGERS    10
+  #define NKRO_INTERFACE        4  // N-key rollover kbd
+  #define NKRO_ENDPOINT         6
+  #define NKRO_SIZE             32
+  #define NKRO_REPORT_KEYS      ( NKRO_SIZE - 1 )
+  #define NKRO_INTERVAL         1
   #define ENDPOINT1_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG   ENDPOINT_RECEIVE_ONLY
   #define ENDPOINT3_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT4_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT5_CONFIG   ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT6_CONFIG   ENDPOINT_TRANSIMIT_ONLY
 
 #elif defined(USB_HID_TOUCHSCREEN)
   #define VENDOR_ID    0x16C0
@@ -305,9 +328,9 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define PRODUCT_NAME    {'K','e','y','b','o','a','r','d','/','M','o','u','s','e','/','T','o','u','c','h','s','c','r','e','e','n'}
   #define PRODUCT_NAME_LEN   26
   #define EP0_SIZE     64
-  #define NUM_ENDPOINTS         6
+  #define NUM_ENDPOINTS         7
   #define NUM_USB_BUFFERS 20
-  #define NUM_INTERFACE      5
+  #define NUM_INTERFACE      6
   #define SEREMU_INTERFACE      2  // Serial emulation
   #define SEREMU_TX_ENDPOINT    1
   #define SEREMU_TX_SIZE        64
@@ -331,12 +354,18 @@ let me know?  http://forum.pjrc.com/forums/4-Suggestions-amp-Bug-Reports
   #define MULTITOUCH_ENDPOINT   5
   #define MULTITOUCH_SIZE       8
   #define MULTITOUCH_FINGERS    10
+  #define NKRO_INTERFACE        5  // N-key rollover kbd
+  #define NKRO_ENDPOINT         7
+  #define NKRO_SIZE             32
+  #define NKRO_REPORT_KEYS      ( NKRO_SIZE - 1 )
+  #define NKRO_INTERVAL         1
   #define ENDPOINT1_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT2_CONFIG   ENDPOINT_RECEIVE_ONLY
   #define ENDPOINT3_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT4_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT5_CONFIG   ENDPOINT_TRANSIMIT_ONLY
   #define ENDPOINT6_CONFIG   ENDPOINT_TRANSIMIT_ONLY
+  #define ENDPOINT7_CONFIG   ENDPOINT_TRANSIMIT_ONLY
 
 #elif defined(USB_MIDI)
   #define VENDOR_ID    0x16C0
diff --git a/avr/cores/teensy3/usb_dev.h b/avr/cores/teensy3/usb_dev.h
index 1233d7f..4de8757 100644
--- a/avr/cores/teensy3/usb_dev.h
+++ b/avr/cores/teensy3/usb_dev.h
@@ -90,6 +90,13 @@ extern uint8_t keyboard_idle_count;
 extern volatile uint8_t keyboard_leds;
 #endif
 
+#ifdef NKRO_INTERFACE
+extern uint8_t nkro_report_data[NKRO_SIZE];
+extern uint8_t nkro_protocol;
+extern uint8_t nkro_idle_config;
+extern uint8_t nkro_idle_count;
+#endif
+
 #ifdef MIDI_INTERFACE
 extern void usb_midi_flush_output(void);
 #endif
diff --git a/avr/cores/teensy3/usb_inst.cpp b/avr/cores/teensy3/usb_inst.cpp
index 224c13d..8987850 100644
--- a/avr/cores/teensy3/usb_inst.cpp
+++ b/avr/cores/teensy3/usb_inst.cpp
@@ -72,6 +72,9 @@ uint8_t usb_joystick_class::manual_mode = 0;
 usb_serial_class Serial;
 #endif
 
+#ifdef NKRO_INTERFACE
+usb_nkro_class Nkro;
+#endif
 
 #else // F_CPU < 20 MHz
 
diff --git a/avr/cores/teensy3/usb_nkro.c b/avr/cores/teensy3/usb_nkro.c
new file mode 100644
index 0000000..5fc22f8
--- /dev/null
+++ b/avr/cores/teensy3/usb_nkro.c
@@ -0,0 +1,132 @@
+#include "usb_dev.h"
+#include "usb_nkro.h"
+#include "core_pins.h" // for yield()
+#include "keylayouts.h"
+//#include "HardwareSerial.h"
+#include <string.h> // for memcpy()
+
+#ifdef NKRO_INTERFACE // defined by usb_dev.h -> usb_desc.h
+
+// byte0: which modifier keys are currently pressed
+//  1=left ctrl,    2=left shift,   4=left alt,    8=left gui
+//  16=right ctrl, 32=right shift, 64=right alt, 128=right gui
+// bytes1-NKRO_SIZE: which keys are currently pressed, one bit
+// per key for codes 0 to ((8*NKRO_REPORT_SIZE) - 1)
+uint8_t nkro_report_data[NKRO_SIZE];
+
+// protocol setting from the host.  We use exactly the same report
+// either way, so this variable only stores the setting since we
+// are required to be able to report which setting is in use.
+uint8_t nkro_protocol=1;
+
+// the idle configuration, how often we send the report to the
+// host (ms * 4) even when it hasn't changed
+uint8_t nkro_idle_config=125;
+
+// count until idle timeout
+uint8_t nkro_idle_count=0;
+
+
+// NKRO Keyboard
+void usb_nkro_reset_keys()
+{
+    uint8_t index;
+    for (index=0; index < NKRO_SIZE; index++)
+    {
+        nkro_report_data[index] = 0;
+    }
+}
+
+void usb_nkro_reset_key(uint8_t usb_keycode)
+{
+    uint8_t bit = usb_keycode % 8;
+    uint8_t byte = (usb_keycode / 8) + 1;
+
+    if (usb_keycode >= 240 && usb_keycode <= 247)
+    {
+        // Reset a modifier key
+        nkro_report_data[0] &= ~(1<< bit);
+    }
+    else if (byte > 0 && byte <= NKRO_REPORT_KEYS)
+    {
+        nkro_report_data[byte] &= ~(1 << bit);
+    }
+}
+
+void usb_nkro_set_key(uint8_t usb_keycode)
+{
+    uint8_t bit = usb_keycode % 8;
+    uint8_t byte = (usb_keycode / 8) + 1;
+
+    if (usb_keycode >= 240 && usb_keycode <= 247)
+    {
+        // Reset a modifier key
+        nkro_report_data[0] |= (1 << bit);
+    }
+    else if (byte > 0 && byte <= NKRO_REPORT_KEYS)
+    {
+        nkro_report_data[byte] |= (1 << bit);
+    }
+}
+
+// Maximum number of transmit packets to queue so we don't starve other endpoints for memory
+#define TX_PACKET_LIMIT 4
+
+static uint8_t transmit_previous_timeout=0;
+
+// When the PC isn't listening, how long do we wait before discarding data?
+#define TX_TIMEOUT_MSEC 50
+
+#if F_CPU == 240000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1600)
+#elif F_CPU == 216000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1440)
+#elif F_CPU == 192000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1280)
+#elif F_CPU == 180000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1200)
+#elif F_CPU == 168000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1100)
+#elif F_CPU == 144000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 932)
+#elif F_CPU == 120000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 764)
+#elif F_CPU == 96000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 596)
+#elif F_CPU == 72000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 512)
+#elif F_CPU == 48000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 428)
+#elif F_CPU == 24000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 262)
+#endif
+
+
+int usb_nkro_send_nkro_now(void)
+{
+        uint32_t wait_count=0;
+        usb_packet_t *tx_packet;
+
+  while (1) {
+     if (!usb_configuration) {
+        return -1;
+     }
+     if (usb_tx_packet_count(NKRO_ENDPOINT) < TX_PACKET_LIMIT) {
+        tx_packet = usb_malloc();
+        if (tx_packet) break;
+     }
+     if (++wait_count > TX_TIMEOUT || transmit_previous_timeout) {
+        transmit_previous_timeout = 1;
+        return -1;
+     }
+     yield();
+  }
+  memcpy(tx_packet->buf, nkro_report_data, NKRO_SIZE);
+  tx_packet->len = NKRO_SIZE;
+  usb_tx(NKRO_ENDPOINT, tx_packet);
+
+    return 0;
+
+}
+
+#endif // NKRO_INTERFACE
diff --git a/avr/cores/teensy3/usb_nkro.h b/avr/cores/teensy3/usb_nkro.h
new file mode 100644
index 0000000..ea1c947
--- /dev/null
+++ b/avr/cores/teensy3/usb_nkro.h
@@ -0,0 +1,43 @@
+#ifndef USBnkro_h_
+#define USBnkro_h_
+
+#include "usb_desc.h"
+#include "keylayouts.h"
+
+#if defined (NKRO_INTERFACE)
+
+#include <inttypes.h>
+
+// C language implementation
+#ifdef __cplusplus
+extern "C" {
+#endif
+void usb_nkro_reset_keys();
+void usb_nkro_reset_key(uint8_t key);
+void usb_nkro_set_key(uint8_t key);
+int usb_nkro_send_nkro_now();
+#ifdef __cplusplus
+}
+#endif
+
+
+
+// C++ interface
+#ifdef __cplusplus
+#include "Stream.h"
+
+class usb_nkro_class
+{
+        public:
+        void reset_keys() { usb_nkro_reset_keys(); }
+        void reset_key(uint8_t key) { usb_nkro_reset_key(key); }
+        void set_key(uint8_t key) { usb_nkro_set_key(key); }
+        int send_nkro_now(void) { return usb_nkro_send_nkro_now(); }
+};
+
+extern usb_nkro_class Nkro;
+
+#endif // __cplusplus
+
+#endif // NKRO_INTERFACE
+#endif // USBnkro_h_
diff --git a/avr/cores/teensy3/usb_undef.h b/avr/cores/teensy3/usb_undef.h
index cbd8c83..af1c246 100644
--- a/avr/cores/teensy3/usb_undef.h
+++ b/avr/cores/teensy3/usb_undef.h
@@ -251,6 +251,21 @@
 #ifdef MTP_EVENT_INTERVAL
 #undef MTP_EVENT_INTERVAL
 #endif
+#ifdef NKRO_INTERFACE
+#undef NKRO_INTERFACE
+#endif
+#ifdef NKRO_ENDPOINT
+#undef NKRO_ENDPOINT
+#endif
+#ifdef NKRO_SIZE
+#undef NKRO_SIZE
+#endif
+#ifdef NKRO_REPORT_KEYS
+#undef NKRO_REPORT_KEYS
+#endif
+#ifdef NKRO_INTERVAL
+#undef NKRO_INTERVAL
+#endif
 #ifdef ENDPOINT1_CONFIG
 #undef ENDPOINT1_CONFIG
 #endif
@@ -296,4 +311,6 @@
 #ifdef ENDPOINT15_CONFIG
 #undef ENDPOINT15_CONFIG
 #endif
-
+#ifdef ENDPOINT16_CONFIG
+#undef ENDPOINT16_CONFIG
+#endif
-- 
2.20.1
@Ayehavgunne
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This worked! Even though I couldn't use the patch file and had to apply the changes manually. I now have NKRO with my Teensy 3.6. Thanks!

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