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/* 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 "kint41.h"
void matrix_init_kb(void) {
matrix_init_user();
// Turn on the Teensy 4.x Power LED:
#define LED_POWER LINE_PIN13
setPinOutput(LED_POWER);
writePinHigh(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(void) {
// 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.
// 600 cycles at 0.6 cycles/ns == 1μs
const uint32_t cycles_per_us = 600;
delay_inline(10 * cycles_per_us);
}
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