feat: add split keyboard functionality

TODO: add tests, fix bugs, etc.

CMakeLists.txt

@@ -81,6 +81,7 @@ add_library(squirrel STATIC
         src/squirrel_consumer.c
         src/squirrel_init.c
         src/squirrel_keymap.c
+        src/squirrel_split.c
         )
 
 target_include_directories(squirrel PRIVATE include)

include/squirrel_consumer.h

@@ -17,5 +17,8 @@ void consumer_activate_consumer_code(uint16_t consumer_code);
 void consumer_deactivate_consumer_code(uint16_t consumer_code);
 // consumer_get_consumer_code returns the currently active consumer code.
 uint16_t consumer_get_consumer_code();
-
+// consumer_get_local_consumer_code returns the currently active consumer code
+// without considering any remote boards. This is only useful in split
+// keyboards.
+uint16_t consumer_get_local_consumer_code();
 #endif

include/squirrel_init.h

@@ -1,5 +1,4 @@
-#ifndef SQUIRREL_INIT_H
-#define SQUIRREL_INIT_H
+#pragma once
+
 enum squirrel_error
 squirrel_init(void); // Initialize the keyboard with the total number of keys.
-#endif

include/squirrel_keyboard.h

@@ -16,12 +16,20 @@ void keyboard_deactivate_keycode(uint8_t keycode);
 // keycodes. 6 is the maximum number of keycodes that can be sent over USB HID.
 // If there are no keycodes, the function will return false.
 bool keyboard_get_keycodes(uint8_t (*active_keycodes)[6]);
+// keyboard_get_local_keycodes populates the provided array with the first 6
+// active keycodes without considering the input of other connected boards. This
+// is only useful for split keyboards.
+void keyboard_get_local_keycodes(uint8_t (*active_keycodes)[6]);
 
 // keyboard_activate_modifier marks the provided modifier as active.
 void keyboard_activate_modifier(uint8_t modifier);
 // keyboard_deactivate_modifier marks the provided modifier as inactive.
 void keyboard_deactivate_modifier(uint8_t modifier);
 // keyboard_get_modifiers returns a bitfield of active modifiers.
 uint8_t keyboard_get_modifiers();
+// keyboard_get_local_modifiers returns a bitfield of active modifiers without
+// considering the input of other connected boards. This is only useful for
+// split keyboards.
+uint8_t keyboard_get_local_modifiers();
 
 #endif

include/squirrel_split.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stdint.h>
+
+// get_packet takes a pointer to a 9-byte array and fills it with the data for
+// the packet to be sent.
+void get_packet(uint8_t (*packet)[9]);
+
+extern uint8_t remote_keycodes[6];
+extern uint8_t remote_modifiers;
+extern uint16_t remote_consumer_code;

src/squirrel_consumer.c

@@ -1,4 +1,5 @@
 #include "squirrel_consumer.h"
+#include "squirrel_split.h"
 #include <stdint.h>
 
 uint16_t consumer_code = 0;
@@ -9,4 +10,10 @@ void consumer_deactivate_consumer_code(uint16_t code) {
     consumer_code = 0;
   }
 }
-uint16_t consumer_get_consumer_code() { return consumer_code; }
+uint16_t consumer_get_consumer_code() {
+  if (consumer_code != 0) {
+    return consumer_code;
+  }
+  return remote_consumer_code;
+}
+uint16_t consumer_get_local_consumer_code() { return consumer_code; }

src/squirrel_keyboard.c

@@ -1,6 +1,8 @@
 #include "squirrel_keyboard.h"
+#include "squirrel_split.h"
 #include <stdbool.h>
 #include <stdint.h>
+#include <string.h>
 
 bool keyboard_keycodes[256] = {false};
 uint8_t keyboard_modifiers = 0;
@@ -12,9 +14,10 @@ void keyboard_deactivate_keycode(uint8_t keycode) {
   keyboard_keycodes[keycode] = false;
 }
 bool keyboard_get_keycodes(uint8_t (*active_keycodes)[6]) {
+  memset(*active_keycodes, 0, 6);
   uint8_t active_keycodes_index = 0;
   for (int i = 0; (i <= 0xFF) && active_keycodes_index < 6; i++) {
-    if (!keyboard_keycodes[i]) {
+    if (!keyboard_keycodes[i] && !remote_keycodes[i]) {
       continue;
     }
     (*active_keycodes)[active_keycodes_index] = i;
@@ -23,10 +26,25 @@ bool keyboard_get_keycodes(uint8_t (*active_keycodes)[6]) {
   return active_keycodes_index != 0;
 }
 
+void keyboard_get_local_keycodes(uint8_t (*active_keycodes)[6]) {
+  memset(*active_keycodes, 0, 6);
+  uint8_t active_keycodes_index = 0;
+  for (int i = 0; (i <= 0xFF) && active_keycodes_index < 6; i++) {
+    if (!keyboard_keycodes[i]) {
+      continue;
+    }
+    (*active_keycodes)[active_keycodes_index] = i;
+    active_keycodes_index++;
+  }
+}
+
 void keyboard_activate_modifier(uint8_t modifier) {
   keyboard_modifiers |= modifier;
 }
 void keyboard_deactivate_modifier(uint8_t modifier) {
   keyboard_modifiers &= ~modifier;
 }
-uint8_t keyboard_get_modifiers() { return keyboard_modifiers; }
+uint8_t keyboard_get_modifiers() {
+  return keyboard_modifiers | remote_modifiers;
+}
+uint8_t keyboard_get_local_modifiers() { return keyboard_modifiers; }

src/squirrel_split.c

@@ -0,0 +1,27 @@
+#include "squirrel_split.h"
+#include "squirrel.h"
+#include "squirrel_consumer.h"
+#include "squirrel_keyboard.h"
+#include <stdint.h>
+#include <string.h>
+
+void get_packet(uint8_t (*packet)[9]) {
+  memset(*packet, 0, 9);
+  uint8_t local_keycodes[6] = {0};
+  keyboard_get_local_keycodes(&local_keycodes);
+  memcpy(packet, local_keycodes, 6);             // 0th to 5th byte
+  (*packet)[6] = keyboard_get_local_modifiers(); // 6th byte
+  uint16_t consumer = consumer_get_local_consumer_code();
+  (*packet)[7] = consumer & 0xFF; // 7th byte
+  (*packet)[8] = consumer >> 8;   // 8th byte
+}
+
+uint8_t remote_keycodes[6] = {0};
+uint8_t remote_modifiers = 0;
+uint16_t remote_consumer_code = 0;
+
+void process_packet(uint8_t (*packet)[9]) {
+  memcpy(remote_keycodes, *packet, 6);                       // 0th to 5th byte
+  remote_modifiers = (*packet)[6];                           // 6th byte
+  remote_consumer_code = (*packet)[7] | ((*packet)[8] << 8); // 7th and 8th byte
+}