[Keyboard] Helix add split common option (#7718)

* is_master, has_usb() move to rev2.[hc]

* Do recent helix/rev2 changes to helix/pico as well.

helix/pico/matrix.c: remove 'is_master'
helix/pico/pico.c: add 'is_master'
helix/pico/pico.h: add 'has_usb()' macro
helix/pico/split_util.c: remove 'setup_handedness()' 'has_usb()', add 'is_helix_master()' etc

* add HELIX=scan option into {rev2/pico}/local_features.mk

Made DEBUG_MATRIX_SCAN_RATE easy to use.

* Changed rules.mk to link "helix/local_drivers/ssd1306.c" only when OLED_ENABLE = yes.

* Added option to use split_common for helix/rev2, helix/pico keyboard.

how to build:
 ### build helix/pico (HelixPico) with helix current codes
  $ make helix/pico:KEY_MAP
  $ make helix/pico/back:KEY_MAP

 ### build helix/rev2 (Helix or Helix beta) with helix current codes
  $ make helix:KEY_MAP
  $ make helix/rev2/back:KEY_MAP
  $ make helix/rev2/under:KEY_MAP
  $ make helix/rev2/oled:KEY_MAP
  $ make helix/rev2/oled/back:KEY_MAP
  $ make helix/rev2/oled/under:KEY_MAP

 ### build helix/pico (HelixPico) with split_common codes
  $ make helix/pico/sc:KEY_MAP
  $ make helix/pico/sc/back:KEY_MAP
  $ make helix/pico/sc/under:KEY_MAP

 ### build helix/rev2 (Helix) with split_common codes
  $ make helix/rev2/sc:KEY_MAP
  $ make helix/rev2/sc/back:KEY_MAP
  $ make helix/rev2/sc/under:KEY_MAP
  $ make helix/rev2/sc/oled:KEY_MAP
  $ make helix/rev2/sc/oledback:KEY_MAP
  $ make helix/rev2/sc/oledunder:KEY_MAP

* add matrix_slave_scan_user() to helix/rev2/rev2.c, helix/pico/pico.h

* Changed 'helix:xulkal' to always use split_common and removed ad hoc code.

Added the following line to 'helix/rev2/keymaps/xulkal/rules.mk':

        SPLIT_KEYBOARD = yes

Removed the following ad hoc code from 'users/xulkal/custom_oled.c':

        #if KEYBOARD_helix_rev2
        extern uint8_t is_master;
        bool is_keyboard_master(void) { return is_master; }
        #endif

* add '#define DIODE_DIRECTION COL2ROW' into helix/{rev2|pico}/config.h

This commit does not change the build result.

* update helix readme

* keyboards/helix/readme.md
* keyboards/helix/pico/keymaps/default/readme.md
* keyboards/helix/rev2/keymaps/default/readme.md

Co-authored-by: mtei <2170248+mtei@users.noreply.github.com>

keyboards/helix/pico/split_util.c

@@ -7,6 +7,7 @@
 #include "split_util.h"
 #include "matrix.h"
 #include "keyboard.h"
+#include "wait.h"
 
 #ifdef USE_MATRIX_I2C
 #  include "i2c.h"
@@ -14,21 +15,65 @@
 #  include "serial.h"
 #endif
 
+#ifdef EE_HANDS
+#    include "eeconfig.h"
+#endif
+
+#ifndef SPLIT_USB_TIMEOUT
+  #define SPLIT_USB_TIMEOUT 2500
+#endif
+
 volatile bool isLeftHand = true;
 
-static void setup_handedness(void) {
-  #ifdef EE_HANDS
-    isLeftHand = eeprom_read_byte(EECONFIG_HANDEDNESS);
-  #else
-    // I2C_MASTER_RIGHT is deprecated, use MASTER_RIGHT instead, since this works for both serial and i2c
-    #if defined(I2C_MASTER_RIGHT) || defined(MASTER_RIGHT)
-      isLeftHand = !has_usb();
-    #else
-      isLeftHand = has_usb();
-    #endif
-  #endif
+bool waitForUsb(void) {
+    for (uint8_t i = 0; i < (SPLIT_USB_TIMEOUT / 100); i++) {
+        // This will return true of a USB connection has been established
+        if (UDADDR & _BV(ADDEN)) {
+            return true;
+        }
+        wait_ms(100);
+    }
+
+    // Avoid NO_USB_STARTUP_CHECK - Disable USB as the previous checks seem to enable it somehow
+    (USBCON &= ~(_BV(USBE) | _BV(OTGPADE)));
+
+    return false;
 }
 
+bool is_keyboard_left(void) {
+#if defined(SPLIT_HAND_PIN)
+    // Test pin SPLIT_HAND_PIN for High/Low, if low it's right hand
+    setPinInput(SPLIT_HAND_PIN);
+    return readPin(SPLIT_HAND_PIN);
+#elif defined(EE_HANDS)
+    return eeconfig_read_handedness();
+#elif defined(MASTER_RIGHT)
+    return !is_helix_master();
+#endif
+
+    return is_helix_master();
+}
+
+bool is_helix_master(void) {
+    static enum { UNKNOWN, MASTER, SLAVE } usbstate = UNKNOWN;
+
+    // only check once, as this is called often
+    if (usbstate == UNKNOWN) {
+#if defined(SPLIT_USB_DETECT)
+        usbstate = waitForUsb() ? MASTER : SLAVE;
+#elif defined(__AVR__)
+        USBCON |= (1 << OTGPADE);  // enables VBUS pad
+        wait_us(5);
+
+        usbstate = (USBSTA & (1 << VBUS)) ? MASTER : SLAVE;  // checks state of VBUS
+#else
+        usbstate = MASTER;
+#endif
+    }
+
+    return (usbstate == MASTER);
+ }
+
 static void keyboard_master_setup(void) {
 
 #ifdef USE_MATRIX_I2C
@@ -47,24 +92,13 @@ static void keyboard_slave_setup(void) {
 #endif
 }
 
-bool has_usb(void) {
-   USBCON |= (1 << OTGPADE); //enables VBUS pad
-   _delay_us(5);
-   return (USBSTA & (1<<VBUS));  //checks state of VBUS
-}
-
 void split_keyboard_setup(void) {
-   setup_handedness();
+   isLeftHand = is_keyboard_left();
 
-   if (has_usb()) {
+   if (is_helix_master()) {
       keyboard_master_setup();
    } else {
       keyboard_slave_setup();
    }
    sei();
 }
-
-// this code runs before the usb and keyboard is initialized
-void matrix_setup(void) {
-    split_keyboard_setup();
-}