Touch Sensing Library (STM32Cube_FW_L0_V1.12.1) uses delay which depends on fixed system clock!
In STM32Cube_FW_L0_V1.12.1\Middlewares\ST\STM32_TouchSensing_Library\src\tsl.c, the value TSL_Globals.DelayDischarge is initialized in TSL_Init() as:
TSL_Globals.DelayDischarge = (uint32_t)((TSLPRM_DELAY_DISCHARGE_ALL * (uint32_t)(SystemCoreClock /1000000)) / 72); It is noticeable that :
- 72 is used as magicNumber
- DelayDischarge also changes when the SystemClock is changed, i.e. when the main clock of the STM32 is changed, the behavior of the touch evaluation could change unexpectedly.
- What is with IAR Compiler?
TSL_Globals.DelayDischarge is only used for the SoftDelay() function tsl_acq_tsc.c
/**
* @brief Software delay (private routine)
* @param val Wait delay
* @retval None
* @note Measurements done with HCLK=72MHz and Keil/MDK-ARM compiler
* val = 500: ~ 63us
* val = 1000: ~126us
* val = 2000: ~251us
*/
void SoftDelay(uint32_t val)
{
volatile uint32_t idx;
for (idx = val; idx > 0; idx--)
{}
}This is therefore only a software delay. The commentary shows that the approximate values were measured with a main clock of HCLK=72MHz. This is presumably where the magicNumber 72 above comes from. So if the value of DelayDischarge should not depend on the SystemClock, the assignment in TSL_Init() would probably have to be changed.
The question is whether other delay functions are available for SoftDelay(), which delay a microsecond duration independently of the system clock so that the touch parameters (especially TSLPRM_DELAY_DISCHARGE_ALL) do not depend on the system clock.