Software-Controlled Slew Rate

[electricalhog]

Not in issue yet because I popped another MCU and need to figure out how that has anything to do with anything, really.

The concept should be complete but the implementation is missing a separate folder and typedef during the prototyping stage. I was hoping that the same ISR could be reused with global static flags to adjust both the current and voltage DAC outputs.

PD_Charger/STM32CubeIDE/PD Charger/Core/Src/main.c

Lines 59 to 68 in 6ce36f3

	/* USER CODE BEGIN PV */
	static double volts;
	static double amps;
	static uint32_t DAC_volts;
	static uint32_t DAC_amps;
	const int slew_volts = 1; // multiples of 12mV/us
	const int slew_amps = 1; //multiples of 2.4mA/us
	static char voltage_set;
	static char current_set;
	/* USER CODE END PV */

Global or otherwise safe-namespace variables

PD_Charger/STM32CubeIDE/PD Charger/Core/Src/main.c

Lines 92 to 151 in e8d0009

	/* USER CODE BEGIN 0 */
	static setVoltage(double voltage){
	voltage_set = 0;
	volts = voltage; // save local value to global for safe-keeping
	DAC_volts = HAL_DAC_GetValue(&hdac3, DAC_CHANNEL_1); // save starting condition from DAC
	HAL_TIM_Base_Start_IT(&htim3);
	}
	static setCurrent(double current){
	current_set = 0;
	amps = current; // save local value to global for safe-keeping
	DAC_amps = HAL_DAC_GetValue(&hdac1, DAC_CHANNEL_1); // save starting condition from DAC
	HAL_TIM_Base_Start_IT(&htim3);
	}
	static int DAC_Voltage(double voltage){ // voltage to DAC scaling function
	int v = (int)(voltage-5.2733)/0.0119755;
	return (v>0) ? v : 0;
	}
	static int DAC_Current(double current){ // current to DAC scaling function
	int c = (int)((current*0.02*10)+0.25)*(4095/2);
	return (c>0) ? c : 0;
	}
	void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
	{
	if (htim->Instance == TIM3) // 1us ISR for soft-slewing
	{
	if(voltage_set != 1) // voltage soft-slew active
	{
	if (DAC_volts < DAC_Voltage(volts)) // has not reached set-point
	{
	DAC_volts += slew_volts; // increment by constant
	HAL_DAC_SetValue(&hdac3, DAC_CHANNEL_1, DAC_ALIGN_12B_R, DAC_volts); // write to DAC
	}
	else
	{
	voltage_set = 1;
	}
	}
	if(current_set != 1) // current soft-slew active
	{
	if (DAC_amps < DAC_Current(amps)) // has not reached set-point
	{
	DAC_amps += slew_amps; // increment by constant
	HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1, DAC_ALIGN_12B_R, DAC_amps); // write to DAC
	}
	else
	{
	current_set = 1;
	}
	}
	if (current_set && voltage_set) // soft-slew complete
	{
	HAL_TIM_Base_Stop_IT(&htim3); // turn of timer
	}
	}
	}
	/* USER CODE END 0 */

Scaling functions, setting functions, and timer ISR