From 21a00b7f020a87af1fbeb31b96a17e0f25a34e96 Mon Sep 17 00:00:00 2001
From: Joel Challis <git@zvecr.com>
Date: Sat, 15 Aug 2020 22:22:11 +0100
Subject: ARM backlight - timer implementation (#8291)
* Add GPT timer based backlight driver
* Update to tim15 to avoid conflict with audio
* Update quantum/backlight/backlight_timer.c
---
common_features.mk | 2 +-
.../chibios/GENERIC_STM32_F303XC/configs/mcuconf.h | 2 +-
quantum/backlight/backlight_timer.c | 167 +++++++++++++++++++++
3 files changed, 169 insertions(+), 2 deletions(-)
create mode 100644 quantum/backlight/backlight_timer.c
diff --git a/common_features.mk b/common_features.mk
index f9fca4669..2806544f8 100644
--- a/common_features.mk
+++ b/common_features.mk
@@ -264,7 +264,7 @@ ifeq ($(strip $(BACKLIGHT_CUSTOM_DRIVER)), yes)
BACKLIGHT_DRIVER := custom
endif
-VALID_BACKLIGHT_TYPES := pwm software custom
+VALID_BACKLIGHT_TYPES := pwm timer software custom
BACKLIGHT_ENABLE ?= no
BACKLIGHT_DRIVER ?= pwm
diff --git a/platforms/chibios/GENERIC_STM32_F303XC/configs/mcuconf.h b/platforms/chibios/GENERIC_STM32_F303XC/configs/mcuconf.h
index 3b1588348..ac2d9a1ee 100644
--- a/platforms/chibios/GENERIC_STM32_F303XC/configs/mcuconf.h
+++ b/platforms/chibios/GENERIC_STM32_F303XC/configs/mcuconf.h
@@ -144,7 +144,7 @@
#define STM32_GPT_USE_TIM6 TRUE
#define STM32_GPT_USE_TIM7 TRUE
#define STM32_GPT_USE_TIM8 TRUE
-#define STM32_GPT_USE_TIM15 FALSE
+#define STM32_GPT_USE_TIM15 TRUE
#define STM32_GPT_USE_TIM16 FALSE
#define STM32_GPT_USE_TIM17 FALSE
#define STM32_GPT_TIM1_IRQ_PRIORITY 7
diff --git a/quantum/backlight/backlight_timer.c b/quantum/backlight/backlight_timer.c
new file mode 100644
index 000000000..c32c35c15
--- /dev/null
+++ b/quantum/backlight/backlight_timer.c
@@ -0,0 +1,167 @@
+#include "quantum.h"
+#include "backlight.h"
+#include "backlight_driver_common.h"
+#include "debug.h"
+
+#ifndef BACKLIGHT_GPT_DRIVER
+# define BACKLIGHT_GPT_DRIVER GPTD15
+#endif
+
+// Platform specific implementations
+static void backlight_timer_configure(bool enable);
+static void backlight_timer_set_duty(uint16_t duty);
+static uint16_t backlight_timer_get_duty(void);
+
+// See http://jared.geek.nz/2013/feb/linear-led-pwm
+static uint16_t cie_lightness(uint16_t v) {
+ if (v <= 5243) // if below 8% of max
+ return v / 9; // same as dividing by 900%
+ else {
+ uint32_t y = (((uint32_t)v + 10486) << 8) / (10486 + 0xFFFFUL); // add 16% of max and compare
+ // to get a useful result with integer division, we shift left in the expression above
+ // and revert what we've done again after squaring.
+ y = y * y * y >> 8;
+ if (y > 0xFFFFUL) // prevent overflow
+ return 0xFFFFU;
+ else
+ return (uint16_t)y;
+ }
+}
+
+void backlight_init_ports(void) {
+ backlight_pins_init();
+
+ backlight_set(get_backlight_level());
+
+#ifdef BACKLIGHT_BREATHING
+ if (is_backlight_breathing()) {
+ breathing_enable();
+ }
+#endif
+}
+
+void backlight_set(uint8_t level) {
+ if (level > BACKLIGHT_LEVELS) level = BACKLIGHT_LEVELS;
+
+ backlight_pins_off();
+
+ backlight_timer_set_duty(cie_lightness(0xFFFFU / BACKLIGHT_LEVELS * level));
+ backlight_timer_configure(level != 0);
+}
+
+static void backlight_timer_top(void) {
+#ifdef BACKLIGHT_BREATHING
+ if (is_breathing()) {
+ breathing_task();
+ }
+#endif
+
+ if (backlight_timer_get_duty() > 256) {
+ backlight_pins_on();
+ }
+}
+
+static void backlight_timer_cmp(void) { backlight_pins_off(); }
+
+void backlight_task(void) {}
+
+#ifdef BACKLIGHT_BREATHING
+# define BREATHING_STEPS 128
+
+static bool breathing = false;
+static uint16_t breathing_counter = 0;
+
+/* To generate breathing curve in python:
+ * from math import sin, pi; [int(sin(x/128.0*pi)**4*255) for x in range(128)]
+ */
+static const uint8_t breathing_table[BREATHING_STEPS] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 17, 20, 24, 28, 32, 36, 41, 46, 51, 57, 63, 70, 76, 83, 91, 98, 106, 113, 121, 129, 138, 146, 154, 162, 170, 178, 185, 193, 200, 207, 213, 220, 225, 231, 235, 240, 244, 247, 250, 252, 253, 254, 255, 254, 253, 252, 250, 247, 244, 240, 235, 231, 225, 220, 213, 207, 200, 193, 185, 178, 170, 162, 154, 146, 138, 129, 121, 113, 106, 98, 91, 83, 76, 70, 63, 57, 51, 46, 41, 36, 32, 28, 24, 20, 17, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+// Use this before the cie_lightness function.
+static inline uint16_t scale_backlight(uint16_t v) { return v / BACKLIGHT_LEVELS * get_backlight_level(); }
+
+void breathing_task(void) {
+ uint8_t breathing_period = get_breathing_period();
+ uint16_t interval = (uint16_t)breathing_period * 256 / BREATHING_STEPS;
+ // resetting after one period to prevent ugly reset at overflow.
+ breathing_counter = (breathing_counter + 1) % (breathing_period * 256);
+ uint8_t index = breathing_counter / interval % BREATHING_STEPS;
+
+ // printf("index:%u\n", index);
+
+ backlight_timer_set_duty(cie_lightness(scale_backlight((uint16_t)breathing_table[index] * 256)));
+}
+
+bool is_breathing(void) { return breathing; }
+
+void breathing_enable(void) {
+ breathing_counter = 0;
+ breathing = true;
+}
+void breathing_disable(void) { breathing = false; }
+
+void breathing_pulse(void) {
+ backlight_set(is_backlight_enabled() ? 0 : BACKLIGHT_LEVELS);
+ wait_ms(10);
+ backlight_set(is_backlight_enabled() ? get_backlight_level() : 0);
+}
+#endif
+
+#ifdef PROTOCOL_CHIBIOS
+// On Platforms where timers fire every tick and have no capture/top events
+// - fake event in the normal timer callback
+uint16_t s_duty = 0;
+
+static void timerCallback(void) {
+ /* Software PWM
+ * timer:1111 1111 1111 1111
+ * \______/| \_______/____ count(0-255)
+ * \ \______________ unused(1)
+ * \__________________ index of step table(0-127)
+ */
+
+ // this works for cca 65536 irqs/sec
+ static union {
+ uint16_t raw;
+ struct {
+ uint16_t count : 8;
+ uint8_t dummy : 1;
+ uint8_t index : 7;
+ } pwm;
+ } timer = {.raw = 0};
+
+ timer.raw++;
+
+ if (timer.pwm.count == 0) {
+ // LED on
+ backlight_timer_top();
+ } else if (timer.pwm.count == (s_duty / 256)) {
+ // LED off
+ backlight_timer_cmp();
+ }
+}
+
+static void backlight_timer_set_duty(uint16_t duty) { s_duty = duty; }
+static uint16_t backlight_timer_get_duty(void) { return s_duty; }
+
+// ChibiOS - Map GPT timer onto Software PWM
+static void gptTimerCallback(GPTDriver *gptp) {
+ (void)gptp;
+ timerCallback();
+}
+
+static void backlight_timer_configure(bool enable) {
+ static const GPTConfig gptcfg = {1000000, gptTimerCallback, 0, 0};
+
+ static bool s_init = false;
+ if (!s_init) {
+ gptStart(&BACKLIGHT_GPT_DRIVER, &gptcfg);
+ s_init = true;
+ }
+
+ if (enable) {
+ gptStartContinuous(&BACKLIGHT_GPT_DRIVER, gptcfg.frequency / 0xFFFF);
+ } else {
+ gptStopTimer(&BACKLIGHT_GPT_DRIVER);
+ }
+}
+#endif
--
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