Posted on June 21, 2018 at 19:24
I followed some examples to create a CubeMX code to configure TIM1 on my STM32F103C8T6 as an Encoder. My encoder is a cheap 20 PPR one that comes with a breakout board. I've hardware debounced it using a 10K and 0.1uF RC filter. Apart from this the A and B pins are pulled high using 10K resistors.The encoder is set to count from 0 to 19 and based on whether its counting up or down I determine whether the encoder being turned clockwise or counter clockwise. This status is then displayed on a 20x4 HD44780 LCD.
For the most part, this code works but every once in a while I see that the count slips back even when the encoder is being turned so that it counts up. Why is this? Is this an encoder hardware fault? Or is this something to do with software? How do I resolve this?
This is the main while loop that reads the encoder direction and displays the status on the LCD:
while (1)
{
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
if (GetEncoderDirection() == 1) HD44780_Puts(0, 0, 'Clockwise ');
if (GetEncoderDirection() == 0) HD44780_Puts(0, 0, 'Counter clockwise');
//if (GetEncoderDirection() == 2) HD44780_Puts(0, 0, 'Glitch ');
if (GetEncoderButtonState() == 1) HD44780_Puts(0, 3, 'Button pressed!');
else HD44780_Puts(0, 3, g_line1);
}�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
This is the function that gets the encoder direction. A direction value of 1 means the encoder is being turned CW
uint8_t GetEncoderDirection(void) {
uint8_t l_curr_count = htim1.Instance->CNT;
sprintf(buffer, '%d', l_curr_count);
HD44780_Puts(0, 1, ' ');
HD44780_Puts(0, 1, buffer);
if (l_curr_count == 0 && g_last_value == ENCODER_PPR) g_encoder_direction = 1; // moving CW
else if (l_curr_count == ENCODER_PPR && g_last_value == 0) g_encoder_direction = 0; // moving CCW
else if (l_curr_count - g_last_value > 0) g_encoder_direction = 1; // moving CW
else if (l_curr_count - g_last_value < 0) g_encoder_direction = 0; // moving CCW
//else if (l_curr_count - g_last_value == 0) g_encoder_direction = 2; // encoder glitch
g_last_value = l_curr_count;
sprintf(buffer, '%d', g_last_value);
HD44780_Puts(0, 2, ' ');
HD44780_Puts(0, 2, buffer);
return g_encoder_direction;
}
�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
This is the CubeMX generated TIM1 code:
#define ENCODER_PRESCLAER 4 // If this is not set, then the counts are in multiples of 4
#define ENCODER_PPR 19 // (0-19 = 20 PPR)
#define ENCODER_FILTER 15
void MX_TIM1_Init(void)
{
TIM_Encoder_InitTypeDef sConfig;
TIM_MasterConfigTypeDef sMasterConfig;
htim1.Instance = TIM1;
htim1.Init.Prescaler = ENCODER_PRESCLAER;
htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
htim1.Init.Period = ENCODER_PPR;
htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim1.Init.RepetitionCounter = 0;
htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
sConfig.EncoderMode = TIM_ENCODERMODE_TI12;
sConfig.IC1Polarity = TIM_ICPOLARITY_RISING;
sConfig.IC1Selection = TIM_ICSELECTION_DIRECTTI;
sConfig.IC1Prescaler = TIM_ICPSC_DIV1;
sConfig.IC1Filter = ENCODER_FILTER;
sConfig.IC2Polarity = TIM_ICPOLARITY_RISING;
sConfig.IC2Selection = TIM_ICSELECTION_DIRECTTI;
sConfig.IC2Prescaler = TIM_ICPSC_DIV1;
sConfig.IC2Filter = ENCODER_FILTER;
if (HAL_TIM_Encoder_Init(&htim1, &sConfig) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}
}
�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?�?
#stm32-encoder #stm32f103-tim1 #tim1-timer
