forked from forks/qmk_firmware
53 lines
2 KiB
C
53 lines
2 KiB
C
/* Copyright 2020 QMK
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "kint41.h"
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void matrix_init_kb(void) {
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matrix_init_user();
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// Turn on the Teensy 4.x Power LED:
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#define LED_POWER LINE_PIN13
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setPinOutput(LED_POWER);
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writePinHigh(LED_POWER);
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}
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// delay_inline sleeps for |cycles| (e.g. sleeping for F_CPU will sleep 1s).
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// delay_inline assumes the cycle counter has already been initialized and
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// should not be modified, i.e. it is safe to call during keyboard matrix scan.
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//
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// ChibiOS enables the cycle counter in chcore_v7m.c:
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// https://github.com/ChibiOS/ChibiOS/blob/b63023915c304092acb9f33bbab40f3ec07a7f0e/os/common/ports/ARMCMx/chcore_v7m.c#L263
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static void delay_inline(const uint32_t cycles) {
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const uint32_t start = DWT->CYCCNT;
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while ((DWT->CYCCNT - start) < cycles) {
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// busy-loop until time has passed
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}
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}
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void matrix_output_unselect_delay(uint8_t line, bool key_pressed) {
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// Use the cycle counter to do precise timing in microseconds. The ChibiOS
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// thread sleep functions only allow sleep durations starting at 1 tick, which
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// is 100μs in our configuration.
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// Empirically: e.g. 5μs is not enough, will result in keys that don’t work
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// and ghost key presses. 10μs seems to work well.
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// 600 cycles at 0.6 cycles/ns == 1μs
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const uint32_t cycles_per_us = 600;
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delay_inline(10 * cycles_per_us);
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}
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