1 files changed, 59 insertions, 0 deletions
diff --git a/keyboards/handwired/lagrange/lagrange.c b/keyboards/handwired/lagrange/lagrange.c
new file mode 100644
index 0000000000..0c76512c57
--- /dev/null
+++ b/keyboards/handwired/lagrange/lagrange.c
@@ -0,0 +1,59 @@
+/* Copyright 2020 Dimitris Papavasiliou <dpapavas@protonmail.ch>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <LUFA/Drivers/USB/USB.h>
+
+#include "lagrange.h"
+
+#ifndef SPLIT_USB_TIMEOUT_POLL
+#    define SPLIT_USB_TIMEOUT_POLL 10
+#endif
+
+/* Instead of timing out, the slave waits indefinitely for the other
+ * side to signal that it has become master.  This avoids both sides
+ * assuming the slave role when the USB port is powered but not
+ * otherwise active (e.g. when the host is turned off, or suspended).
+ * The SPI SS line is used for signaling.  On power-up it is
+ * configured as input with pull-up enabled.  When one side assumes
+ * the master role, it reconfigures the line for SPI, and pulls it low
+ * to select the slave, which doubles as the signal. */
+
+bool is_keyboard_master(void) {
+    static int8_t is_master = -1;
+
+    if (is_master < 0) {
+        while (readPin(SPI_SS_PIN)) {
+            if (USB_Device_IsAddressSet()) {
+                is_master = 1;
+                return is_master;
+            }
+            wait_ms(SPLIT_USB_TIMEOUT_POLL);
+        }
+
+        is_master = 0;
+
+        USB_Disable();
+        USB_DeviceState = DEVICE_STATE_Unattached;
+    }
+
+    return is_master;
+}
+
+void keyboard_pre_init_kb(void) {
+    setPinInputHigh(SPI_SS_PIN);
+
+    keyboard_pre_init_user();
+}