diff options
| -rw-r--r-- | firmware/main.c | 64 |
1 files changed, 58 insertions, 6 deletions
diff --git a/firmware/main.c b/firmware/main.c index 264d3f5..df35205 100644 --- a/firmware/main.c +++ b/firmware/main.c @@ -2,6 +2,8 @@ /* + ------------------------------------------------------------------------------ + ledcontrol firmware Copyright (C) 2021 xengineering @@ -19,6 +21,19 @@ along with this program. If not, see <https://www.gnu.org/licenses/>. Contact: me@xengineering.eu + + ------------------------------------------------------------------------------ + + This firmware currently has these functions: + - blink the onboard LED C13 + - let an external LED at PB0 fade + + Future features should be: + - adjust the brightness of the external LED by an incremental encoder + - enable / disable the light by pressing a push button (included in encoder) + - offer this functionality via WiFi with an external WiFi-capable board + +------------------------------------------------------------------------------ */ @@ -36,6 +51,12 @@ static void timer_init(void); void tim2_isr(void); +/* main function + +This should give you a brief overview of the control flow. Read the +corresponding function definitions for details about configuration and +implementation. +*/ int main(void) { clock_init(); @@ -47,9 +68,18 @@ int main(void) } +/* Clock initialization + +This function configures the system clock of the microcontroller (sysclk). The +dynamic configuration allows to execute the program faster (high clock speed) +or to save energy (low clock speed). + +Important to notice: On STM32 microcontrollers it is mandatory to enable the +clocks for peripherals and timer / counter units explicitly! +*/ static void clock_init(void) { - // set sysclk to 72 MHz via external 8 MHz crystal + // set system clock to 72 MHz via external 8 MHz crystal and a PLL rcc_clock_setup_pll(&rcc_hse_configs[RCC_CLOCK_HSE8_72MHZ]); // enable clocks for GPIO ports B and C @@ -61,12 +91,10 @@ static void clock_init(void) // enable clock for timer 3 (PWM) rcc_periph_clock_enable(RCC_TIM3); - - // enable clock for alternate functions - rcc_periph_clock_enable(RCC_AFIO); // TODO is this necessary? } +/* Initialization of general purpose inputs and outputs (GPIOs) */ static void gpio_init(void) { // init PC13 onboard LED for blinking @@ -76,7 +104,9 @@ static void gpio_init(void) GPIO_CNF_OUTPUT_PUSHPULL, GPIO13 ); - gpio_clear(GPIOC, GPIO13); // set initial value to 'on' + + // set initial value to 'on' + gpio_clear(GPIOC, GPIO13); // setup PB0 (connected to TIM3_CH3) for PWM gpio_set_mode( @@ -88,6 +118,11 @@ static void gpio_init(void) } +/* Nested Vectored Interrupt Controller (NVIC) setup + +This function configures NVIC. This way the interrupt triggered by +timer / counter units is enabled explicitly. +*/ static void nvic_init(void) { // enable timer 2 interrupt and set priority @@ -96,6 +131,12 @@ static void nvic_init(void) } +/* Timer / counter setup + +This function configures two timer / counter units (TIM2 and TIM3). TIM2 +controls the blinking and fading animation and TIM3 is for the +pulse-width-modulation (PWM) of the external LED. +*/ static void timer_init(void) { // setup timer 2 for blinking @@ -109,6 +150,7 @@ static void timer_init(void) /* enable timer / counter 3 + // TODO: clean the rest of this function ... it is a mess */ /* Clock division and mode */ @@ -139,10 +181,20 @@ static void timer_init(void) } +/* Timer / counter 2 interrupt service routine + +This function is called by the interrupt of timer / counter 2. The function is +not called explicitly in this file but hard-coded in the libopencm3 library. + +The purpose of TIM2 is to blink the onboard LED and to decrement the PWM value +resulting in a increment of brightness. Thus this function defines the logic of +the 'animation' shown by the LEDs. +*/ void tim2_isr(void) { // PWM handling - static uint32_t pwm_value; + static uint32_t pwm_value = 0; // static variable to remember value on next + // function call if (pwm_value == 0) { pwm_value = 65535; } |