Thanks for pointing out the confusing resistor placement.
The point was to light only one LED at a time because I wanted to achieve some form of individual LED brightness control. The brightness of each LED can be adjusted in 10 % increments.
I found I could improve the display smoothness by adjusting the clock settings. With following settings the flicker is minimal:
- AHB Prescaler: /4
- HCLK (MHz): 16
- APB1 Prescaler: /2
- APB1 Peripheral clocks (MHz): 8
- APB1 Timer clocks (MHz): 16
Below is the user code I wrote in STMCubeIDE:
/* USER CODE BEGIN PFP */
void led_task(void);
void drive_anode(int32_t num);
void drive_cathode(int32_t num);
void clear_cathodes(void);
void clear_anodes(void);
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* 0: led off, 1: led on */
uint8_t led_state[32+1] = { 0,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1
};
/* led brightness level from 0 to 10 */
uint8_t led_brightness[32+1] = { 0,
1, 2, 3, 4, 5, 6, 7, 8,
9, 10, 9, 8, 7, 6, 5, 4,
3, 2, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 9, 8, 7, 6
};
GPIO_TypeDef * leda_port[4+1] = { 0,
LEDA0_GPIO_Port, LEDA1_GPIO_Port,
LEDA2_GPIO_Port, LEDA3_GPIO_Port
};
uint16_t leda_pin[4+1] = { 0,
LEDA0_Pin, LEDA1_Pin,
LEDA2_Pin, LEDA3_Pin
};
GPIO_TypeDef * ledc_port[8+1] = { 0,
LEDC0_GPIO_Port, LEDC1_GPIO_Port, LEDC2_GPIO_Port, LEDC3_GPIO_Port,
LEDC4_GPIO_Port, LEDC5_GPIO_Port, LEDC6_GPIO_Port, LEDC7_GPIO_Port
};
uint16_t ledc_pin[8+1] = { 0,
LEDC0_Pin, LEDC1_Pin, LEDC2_Pin, LEDC3_Pin,
LEDC4_Pin, LEDC5_Pin, LEDC6_Pin, LEDC7_Pin
};
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* Configure the system clock */
SystemClock_Config();
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_TIM6_Init();
/* USER CODE BEGIN 2 */
int32_t count = 0;
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE BEGIN 3 */
if (tim6_tick == 1)
{
tim6_tick = 0;
led_task();
++count;
}
if (count >= 4000)
{
count = 0;
uint8_t tmp = led_brightness[32];
for (int32_t i = 32; i >= 1; i--)
{
led_brightness[i] = led_brightness[i - 1];
}
led_brightness[1] = tmp;
}
}
/* USER CODE END 3 */
}
/* USER CODE BEGIN 4 */
void led_task(void)
{
static int32_t n_cathode = 1;
static int32_t n_anode = 1;
static int32_t n_cycles = 0;
const int8_t max_cycles = 10;
int8_t duty;
int32_t num_led;
/* which led */
num_led = (n_anode - 1) * 8 + n_cathode;
/* duty cycle */
duty = led_brightness[num_led];
if ( (led_state[num_led] > 0) && (n_cycles < duty) ) {
drive_anode(n_anode);
drive_cathode(n_cathode);
}
else
{
clear_anodes();
// clear_cathodes();
}
++n_cycles;
if (n_cycles >= max_cycles)
{
n_cycles = 0;
clear_anodes();
clear_cathodes();
++n_cathode;
if (n_cathode > 8)
{
n_cathode = 1;
++n_anode;
if (n_anode > 4)
{
n_anode = 1;
}
}
}
}
void drive_anode(int32_t num)
{
HAL_GPIO_WritePin(leda_port[num], leda_pin[num], GPIO_PIN_RESET);
}
void clear_anodes(void)
{
for (int32_t i = 1; i <= 4; i++)
{
HAL_GPIO_WritePin(leda_port[i], leda_pin[i], GPIO_PIN_SET);
}
}
void drive_cathode(int32_t num)
{
HAL_GPIO_WritePin(ledc_port[num], ledc_pin[num], GPIO_PIN_SET);
}
void clear_cathodes(void)
{
for (int32_t i = 1; i <= 8; i++)
{
HAL_GPIO_WritePin(ledc_port[i], ledc_pin[i], GPIO_PIN_RESET);
}
}
/* USER CODE END 4 */
