Hello, I've reviewed AN5105 and UM1913 application notes and as per the polling based example given in AN5105, I've tried to explore and understand the sample code given for STM32F072B-Disco evaluation board. Though, I was able to modify the sample code and get the sensors to detect touch indicated by the LEDs, I have some confusion and questions as below which I am trying to understand. Your help in explaining this concept is much appreciated!!
1. Resolution and Calculation of Position in the range of 0...255:
How do I calculate the position of the touch on the slider given in this example / in general?
My understanding is that this should be equally divided in the range of 0...255. In this discovery board, as there are 3 sensors configured as Linear Half ended electrode, each position should be (approximately) divided in the range of 255 / 3, isn't it?
Please explain how would I calculate position of the touch on the sensor.
From the header file, these are some configurations that I have been tweaking to understand how to calculate finger position but I am getting all strange LED response of the touch..
#define TSLPRM_USE_3CH_LIN_H (0)
#define TSLPRM_LINROT_RESOLUTION (7)
I am using MyLinRots[0].p_Data->Position structure to compare the position value in the range of 0...255 but not able to understand the correlation of the value and touch. How does Resolution value 1..8 affect this calculation? What's the formula for such correlation? Why is the TSLPRM_LINROT_RESOLUTION configured to 7 with this example? If I change this to any other value in the range of 1..8, I can't get the slider to provide evenly distributed response with 3 Ch. in the position of 0...255.
I am trying to get 4 LEDs to be evenly distributed in the entire slider over the range of 0...255 with the following code:
if(MyLinRots[0].p_Data->StateId == TSL_STATEID_DETECT)
{
//TSLPRM_LINROT_RESOLUTION
if(MyLinRots[0].p_Data->Position >= 1 && MyLinRots[0].p_Data->Position < 60)
{
HAL_GPIO_WritePin(LD4_GPIO_Port, LD3_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD6_GPIO_Port, LD6_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);
}
if(MyLinRots[0].p_Data->Position >= 60 && MyLinRots[0].p_Data->Position < 120)
{
HAL_GPIO_WritePin(LD4_GPIO_Port, LD3_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD6_GPIO_Port, LD6_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);
}
if(MyLinRots[0].p_Data->Position >= 120 && MyLinRots[0].p_Data->Position < 180)
{
HAL_GPIO_WritePin(LD4_GPIO_Port, LD3_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD6_GPIO_Port, LD6_Pin, GPIO_PIN_SET);
}
if(MyLinRots[0].p_Data->Position >= 180 && MyLinRots[0].p_Data->Position < 255)
{
HAL_GPIO_WritePin(LD4_GPIO_Port, LD3_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_SET);
HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD6_GPIO_Port, LD6_Pin, GPIO_PIN_RESET);
}
}
else //if(MyLinRots[0].p_Data->StateId == TSL_STATEID_RELEASE)
{
HAL_GPIO_WritePin(LD4_GPIO_Port, LD3_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD4_GPIO_Port, LD4_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);
HAL_GPIO_WritePin(LD6_GPIO_Port, LD6_Pin, GPIO_PIN_RESET);
}
}
2. How does this calculation and response changes if I configure the same linear sensor available on the F072 Disco board as TSLPRM_USE_3CH_LIN_M1 / M2 / D type electrode design? How does it affect position calculation? How to modify this sensor to act as 4 individual touch keys?
3. How can I modify the code to be interrupt driven?
As I am new to touch library and trying to learn firmware development with touch sensor, please bear with me with the questions above and your time and support is much appreciated..
Thank you.
