From eb41e5e21089da6ae9d65ae75c030ed554509027 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mario=20H=C3=BCttel?= <mario.huettel@gmx.net>
Date: Sat, 16 Oct 2021 23:39:23 +0200
Subject: [PATCH] Implement option byte writing and set brown out level

---
 stm-firmware/main.c                    | 33 ++++++++++++++++++
 stm-firmware/stm-periph/option-bytes.c | 46 ++++++++++++++++++++++++--
 2 files changed, 77 insertions(+), 2 deletions(-)

diff --git a/stm-firmware/main.c b/stm-firmware/main.c
index 373c0b0..c3b51c9 100644
--- a/stm-firmware/main.c
+++ b/stm-firmware/main.c
@@ -49,6 +49,7 @@
 #include <reflow-controller/temp-profile/temp-profile-executer.h>
 #include <reflow-controller/settings/spi-eeprom.h>
 #include <reflow-controller/main-cycle-counter.h>
+#include <stm-periph/option-bytes.h>
 
 static void setup_nvic_priorities(void)
 {
@@ -211,6 +212,35 @@ static inline void handle_boot_status(void)
 	}
 }
 
+/**
+ * @brief Read out the option bytes of the STM32 and program them to the desired values.
+ *
+ * - This function currently forces the brown out level to Level 3.
+ */
+static void check_and_program_opt_bytes(void)
+{
+	struct option_bytes opts;
+	int err;
+
+	/** - Read option bytes */
+	stm_option_bytes_read(&opts);
+
+
+	if (opts.brown_out_level != 0) {
+		/* Set the brown out level to level 3 => highest brown out limit. */
+		opts.brown_out_level = 0;
+		/** - Program the option bytes if brown out level was not set correctly */
+		err = stm_option_bytes_program(&opts);
+
+		/** - If programming failes, enter panic mode */
+		if (err)
+			panic_mode();
+
+		/** - If programming is successful, reset the system to apply new settings */
+		NVIC_SystemReset();
+	}
+}
+
 /**
  * @brief Setup the system.
  *
@@ -220,6 +250,9 @@ static inline void setup_system(void)
 {
 	float tmp;
 
+	/** - Read the option bytes and if necessary program them to the desired values */
+	check_and_program_opt_bytes();
+
 	/** - Setup the NVIC priorities of the core peripherals using interrupts */
 	setup_nvic_priorities();
 
diff --git a/stm-firmware/stm-periph/option-bytes.c b/stm-firmware/stm-periph/option-bytes.c
index 9668de5..3425726 100644
--- a/stm-firmware/stm-periph/option-bytes.c
+++ b/stm-firmware/stm-periph/option-bytes.c
@@ -21,6 +21,16 @@
 #include <stm-periph/option-bytes.h>
 #include <stm32/stm32f4xx.h>
 
+/**
+ * @brief First key for unlocking hte option byte write access
+ */
+#define FLASH_OPTION_KEY1 (0x08192A3BUL)
+
+/**
+ * @brief Second key for unlocking hte option byte write access
+ */
+#define FLASH_OPTION_KEY2 (0x4C5D6E7FUL)
+
 void stm_option_bytes_read(struct option_bytes *opts)
 {
 	uint32_t opt_reg;
@@ -39,10 +49,42 @@ void stm_option_bytes_read(struct option_bytes *opts)
 
 int stm_option_bytes_program(const struct option_bytes *opts)
 {
-	FLASH->OPTKEYR = 0x08192A3BUL;
-	FLASH->OPTKEYR = 0x4C5D6E7FUL;
+	uint32_t reg;
 
+	FLASH->OPTKEYR = FLASH_OPTION_KEY1;
+	FLASH->OPTKEYR = FLASH_OPTION_KEY2;
+
+	__DSB();
+
+	if (FLASH->OPTCR & FLASH_OPTCR_OPTLOCK) {
+		/* Unlocking failed */
+		return -1;
+	}
+
+	reg = FLASH->OPTCR;
+	reg &= ~FLASH_OPTCR_BOR_LEV;
+	reg &= ~FLASH_OPTCR_nRST_STDBY;
+	reg &= ~FLASH_OPTCR_nRST_STOP;
+	reg &= ~FLASH_OPTCR_nWRP;
+	reg &= ~FLASH_OPTCR_RDP;
+	reg &= ~FLASH_OPTCR_WDG_SW;
+
+	reg |= (opts->brown_out_level << 2) & FLASH_OPTCR_BOR_LEV;
+	reg |= (opts->nrst_standby << 7) & FLASH_OPTCR_nRST_STDBY;
+	reg |= (opts->nrst_stop << 6) & FLASH_OPTCR_nRST_STOP;
+	reg |= (opts->nwrpi << 16) & FLASH_OPTCR_nWRP;
+	reg |= (opts->read_protection << 8) & FLASH_OPTCR_RDP;
+	reg |= (opts->wdg_sw << 5) & FLASH_OPTCR_WDG_SW;
+
+	while (FLASH->SR & FLASH_SR_BSY);
+
+	FLASH->OPTCR = reg;
+	FLASH->OPTCR |= FLASH_OPTCR_OPTSTRT;
+	__DSB();
+	while (FLASH->SR & FLASH_SR_BSY);
 
 	FLASH->OPTCR |= FLASH_OPTCR_OPTLOCK;
+
+	__DSB();
 	return 0;
 }