lagrange.c (1938B)
1 /* Copyright 2020 Dimitris Papavasiliou <dpapavas@protonmail.ch> 2 * 3 * This program is free software: you can redistribute it and/or modify 4 * it under the terms of the GNU General Public License as published by 5 * the Free Software Foundation, either version 3 of the License, or 6 * (at your option) any later version. 7 * 8 * This program is distributed in the hope that it will be useful, 9 * but WITHOUT ANY WARRANTY; without even the implied warranty of 10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11 * GNU General Public License for more details. 12 * 13 * You should have received a copy of the GNU General Public License 14 * along with this program. If not, see <https://www.gnu.org/licenses/>. 15 */ 16 17 #include <LUFA/Drivers/USB/USB.h> 18 19 #include "lagrange.h" 20 21 #ifndef SPLIT_USB_TIMEOUT_POLL 22 # define SPLIT_USB_TIMEOUT_POLL 10 23 #endif 24 25 /* Instead of timing out, the slave waits indefinitely for the other 26 * side to signal that it has become master. This avoids both sides 27 * assuming the slave role when the USB port is powered but not 28 * otherwise active (e.g. when the host is turned off, or suspended). 29 * The SPI SS line is used for signaling. On power-up it is 30 * configured as input with pull-up enabled. When one side assumes 31 * the master role, it reconfigures the line for SPI, and pulls it low 32 * to select the slave, which doubles as the signal. */ 33 34 bool is_keyboard_master(void) { 35 static int8_t is_master = -1; 36 37 if (is_master < 0) { 38 while (gpio_read_pin(SPI_SS_PIN)) { 39 if (USB_Device_IsAddressSet()) { 40 is_master = 1; 41 return is_master; 42 } 43 wait_ms(SPLIT_USB_TIMEOUT_POLL); 44 } 45 46 is_master = 0; 47 48 USB_Disable(); 49 USB_DeviceState = DEVICE_STATE_Unattached; 50 } 51 52 return is_master; 53 } 54 55 void keyboard_pre_init_kb(void) { 56 gpio_set_pin_input_high(SPI_SS_PIN); 57 58 keyboard_pre_init_user(); 59 }