From b561906a0a3668e0d6e6a3f6c212998276e6c212 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Tue, 30 Jul 2019 23:54:36 +0200
Subject: [PATCH] Protab: More PWM

---
 protab/timer5-pwm/Makefile |  6 ++++
 protab/timer5-pwm/timer.c  | 72 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100644 protab/timer5-pwm/Makefile
 create mode 100644 protab/timer5-pwm/timer.c

diff --git a/protab/timer5-pwm/Makefile b/protab/timer5-pwm/Makefile
new file mode 100644
index 0000000..9f34630
--- /dev/null
+++ b/protab/timer5-pwm/Makefile
@@ -0,0 +1,6 @@
+ROOT=../..
+BINARY=timer
+OBJS=timer.o
+LIB_OBJS=
+
+include $(ROOT)/mk/bluepill.mk
diff --git a/protab/timer5-pwm/timer.c b/protab/timer5-pwm/timer.c
new file mode 100644
index 0000000..1e64d1a
--- /dev/null
+++ b/protab/timer5-pwm/timer.c
@@ -0,0 +1,72 @@
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/timer.h>
+
+int up = 1;
+int pwm;
+
+void tim4_isr(void)
+{
+	if (TIM_SR(TIM4) & TIM_SR_UIF) {
+		TIM_SR(TIM4) &= ~TIM_SR_UIF;
+		if (up) {
+			pwm += 5;
+			if (pwm == 1000) {
+				pwm = 995;
+				up = 0;
+			}
+		} else {
+			pwm -= 5;
+			if (pwm < 0) {
+				pwm = 5;
+				up = 1;
+			}
+		}
+		timer_set_oc_value(TIM3, TIM_OC3, pwm);
+	}
+}
+
+int main(void)
+{
+	rcc_clock_setup_in_hse_8mhz_out_72mhz();
+	rcc_periph_clock_enable(RCC_GPIOB);
+	rcc_periph_clock_enable(RCC_GPIOC);
+	rcc_periph_clock_enable(RCC_TIM3);
+	rcc_periph_clock_enable(RCC_TIM4);
+	rcc_periph_reset_pulse(RST_TIM3);	// XXX
+	rcc_periph_reset_pulse(RST_TIM4);	// XXX
+
+	// PC13 = BluePill LED
+	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
+	gpio_set(GPIOC, GPIO13);
+
+	// PB0 = TIM3_CH3
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO0);
+
+	timer_set_prescaler(TIM3, 1);		// 72 MHz / 2 = 36 MHz
+	timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM3, 999);		// 36 MHz / 1000 = 36 kHz
+	timer_update_on_overflow(TIM3);
+
+	timer_set_oc_mode(TIM3, TIM_OC3, TIM_OCM_PWM1);
+	timer_set_oc_value(TIM3, TIM_OC3, 50);
+	timer_set_oc_polarity_high(TIM3, TIM_OC3);
+	timer_enable_oc_output(TIM3, TIM_OC3);
+
+	timer_enable_counter(TIM3);
+
+	timer_set_prescaler(TIM4, 35999);	// 72 MHz / 36000 = 2 kHz
+	timer_set_mode(TIM4, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
+	timer_set_period(TIM4, 2);		// 2 kHz / 2 = 1 kHz
+	timer_update_on_overflow(TIM4);
+	timer_enable_irq(TIM4, TIM_DIER_UIE);
+	nvic_enable_irq(NVIC_TIM4_IRQ);
+	timer_enable_counter(TIM4);
+
+	for (;;) {
+		asm volatile ("wfi");
+	}
+
+	return 0;
+}
-- 
2.39.5