qmk_firmware

kint41.c (2184B)

---

 /* Copyright 2020 QMK
  *
  * 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 2 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 <http://www.gnu.org/licenses/>.
  */
 
 #include "quantum.h"
 
 #define LED_POWER LINE_PIN13
 
 void matrix_init_kb(void) {
     matrix_init_user();
 
     // Turn on the Teensy 4.x Power LED:
     gpio_set_pin_output(LED_POWER);
     gpio_write_pin_high(LED_POWER);
 }
 
 // delay_inline sleeps for |cycles| (e.g. sleeping for F_CPU will sleep 1s).
 // delay_inline assumes the cycle counter has already been initialized and
 // should not be modified, i.e. it is safe to call during keyboard matrix scan.
 //
 // ChibiOS enables the cycle counter in chcore_v7m.c:
 // https://github.com/ChibiOS/ChibiOS/blob/b63023915c304092acb9f33bbab40f3ec07a7f0e/os/common/ports/ARMCMx/chcore_v7m.c#L263
 static void delay_inline(const uint32_t cycles) {
     const uint32_t start = DWT->CYCCNT;
     while ((DWT->CYCCNT - start) < cycles) {
         // busy-loop until time has passed
     }
 }
 
 void matrix_output_unselect_delay(uint8_t line, bool key_pressed) {
     // Use the cycle counter to do precise timing in microseconds. The ChibiOS
     // thread sleep functions only allow sleep durations starting at 1 tick, which
     // is 100μs in our configuration.
 
     // Empirically: e.g. 5μs is not enough, will result in keys that don’t work
     // and ghost key presses. 10μs seems to work well.
 
     // On some variants of the hardware, 20μs seems to be required. This was found
     // on a combination of KB600LF+stapelberg v2020-06-30+teensy41.
 
     // 600 cycles at 0.6 cycles/ns == 1μs
     const uint32_t cycles_per_us = 600;
     delay_inline(20 * cycles_per_us);
 }