From f2183c5dacb02d9a50833fba04b04002159941c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mario=20H=C3=BCttel?= <mario.huettel@gmx.net>
Date: Fri, 12 Mar 2021 22:28:00 +0100
Subject: [PATCH] First test code for SK6812 LEDs

---
 firmware/Makefile            |  4 +--
 firmware/main.c              | 27 +++++++++++++++------
 firmware/setup/system_init.c | 28 +++++++++++++++++++--
 firmware/sk6812.S            | 47 ++++++++++++++++++++++++++++++++++++
 4 files changed, 95 insertions(+), 11 deletions(-)
 create mode 100644 firmware/sk6812.S

diff --git a/firmware/Makefile b/firmware/Makefile
index 97717a2..4e927e5 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -12,7 +12,7 @@ endif
 
 #Add Files and Folders below#########################################################
 CFILES 	= main.c syscalls/syscalls.c setup/system_init.c startup/startup_stm32f0xx.c
-ASFILES =
+ASFILES = sk6812.S
 INCLUDEPATH = -Iinclude -Iinclude/cmsis
 
 OBJDIR=obj
@@ -39,7 +39,7 @@ LFLAGS += -mfloat-abi=soft --disable-newlib-supplied-syscalls -nostartfiles
 LFLAGS += -Tstartup/stm32f030.ld -Wl,-Map=$(mapfile).map -Wl,--gc-sections -g
 
 CFLAGS = -c -fmessage-length=0 -mlittle-endian -mthumb -mcpu=cortex-m0 -mthumb-interwork
-CFLAGS += -mfloat-abi=soft -nostartfiles -Wall -g
+CFLAGS += -mfloat-abi=soft -nostartfiles -Wall -g -O3
 
 ####################################################################################
 
diff --git a/firmware/main.c b/firmware/main.c
index c778c4a..3e04baf 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -1,19 +1,32 @@
 #include <stm32f0xx.h>
-
+#include <cmsis/core_cm0.h>
 
 unsigned int i = 0x12345678;
 unsigned char c = 2;
 
-int main(void) {
-	RCC->AHBENR |= RCC_AHBENR_GPIOBEN;
-	GPIOB->MODER |= (1<<1*2);
-	GPIOB->ODR |= (1<<1);
+extern void sk6812_send_led(uint32_t rgbw);
+
+volatile uint32_t wait_tick = 0;
+
+static void wait_for_ticks(uint32_t ticks)
+{
+	wait_tick = 0;
+	while (wait_tick < ticks);
+}
+
+int main(void)
+{
+	RCC->AHBENR |= RCC_AHBENR_GPIOAEN;
+	GPIOA->MODER |= (1<<3*2);
 	SysTick_Config(800000);
 	while(1) {
-		i++;
+		__disable_irq();
+		sk6812_send_led(0x000000FF);
+		__enable_irq();
+		wait_for_ticks(30);
 	}
 }
 
 void SysTick_Handler(void) {
-	GPIOB->ODR ^= (1<<1);
+	wait_tick++;
 }
diff --git a/firmware/setup/system_init.c b/firmware/setup/system_init.c
index 380e59f..c06d710 100644
--- a/firmware/setup/system_init.c
+++ b/firmware/setup/system_init.c
@@ -61,10 +61,34 @@ static void __init_default_clocks(void)
   RCC->CIR = 0x00000000;
 }
 
+void __setup_clocks(void)
+{
+	uint32_t tmp;
+
+	/* TODO: Switch HSE on for better accuracy */
+	
+	/* Switch PLL source to HSI OSC */
+	RCC->CFGR &= ~RCC_CFGR_PLLSRC;
+
+	/* Set PLL multiplication to 12 (4 MHz * 12 = 48 MHz SysClk) */
+	RCC->CFGR |= RCC_CFGR_PLLMUL_3 | RCC_CFGR_PLLMUL_1;
+		
+	/* HSI Already running. Switch on PLL */
+	RCC->CR |= RCC_CR_PLLON;
+	
+	/* Wait for PLL to be ready */
+	while (!(RCC->CR & RCC_CR_PLLRDY));
+	
+	/* Switch System Clock to PLL */
+	tmp = RCC->CFGR;
+	tmp &= ~0x3;
+	tmp |= RCC_CFGR_SW_1;
+	RCC->CFGR = tmp;
+}
 
 void __system_init(void)
 {
 
- __init_default_clocks();
- 
+	__init_default_clocks();
+	__setup_clocks(); 
 }
diff --git a/firmware/sk6812.S b/firmware/sk6812.S
new file mode 100644
index 0000000..9dd764d
--- /dev/null
+++ b/firmware/sk6812.S
@@ -0,0 +1,47 @@
+.global sk6812_send_led
+
+.equ BSRR_REGISTER, 0x48000018
+.equ PINNUM, 3
+.syntax unified
+
+sk6812_send_led:
+	push {lr}
+	push {r4, r5, r6}
+	ldr r1, =BSRR_REGISTER
+	ldr r2, =(1<<PINNUM)
+	ldr r3, =(1<<(PINNUM+16))
+	ldr r4, =32
+	ldr r5, =0x80000000
+_bitloop:
+	tst r0, r5
+	beq sk6812_send_zero	
+	bne sk6812_send_one
+_bitloop_ret:
+	lsls r0, r0, #1
+	subs r4, r4, #1
+	bne _bitloop
+	pop {r4, r5, r6}
+	pop {pc}
+	
+sk6812_send_one:
+	str r2, [r1]
+	ldr r6, =0x5
+	bl wait_r6
+	str r3, [r1]
+	ldr r6, =0x2
+	bl wait_r6
+	b _bitloop_ret
+
+sk6812_send_zero:
+	str r2, [r1]
+	ldr r6, =0x1
+	bl wait_r6
+	str r3, [r1]
+	ldr r6, =0x5
+	bl wait_r6
+	b _bitloop_ret
+	
+wait_r6:
+	subs r6, r6, #1
+	bne wait_r6
+	bx lr