Hi, I'm using STM32F373 for a biosignal measurement project, and I need some help writing firmware to automatically update the SDADC channel gain during execution.
For example, I'm sampling at 100Hz, and after every 100 samples, i want to change the gain based on the minimum and the maximum values during that period.
---------------------
So, my code to determine the maximum and minimum values is:
uint16_t ECG = 0;
uint16_t ECG_channel_max = 0;
uint16_t ECG_channel_min = 0xFFFF;
if (ECG > ECG_channel_max)
{
ECG_channel_max = ECG;
}
if (ECG < ECG_channel_min)
{
ECG_channel_min = ECG;
}
---------------------
The SDADC_Init code to setup the SDADC gain looks something like this:
ConfParamStruct.InputMode = SDADC_INPUT_MODE_SE_ZERO_REFERENCE;
ConfParamStruct.Gain = SDADC_GAIN_4;
ConfParamStruct.CommonMode = SDADC_COMMON_MODE_VSSA;
ConfParamStruct.Offset = 0;
if (HAL_SDADC_PrepareChannelConfig(&hsdadc1, SDADC_CONF_INDEX_0, &ConfParamStruct) != HAL_OK)
{
Error_Handler();
}
if (HAL_SDADC_AssociateChannelConfig(&hsdadc1, SDADC_CHANNEL_6, SDADC_CONF_INDEX_0) != HAL_OK)
{
Error_Handler();
}
---------------------
Then, I'm trying to use a custom function after every 100 samples as followed;
static void updateGain(void)
{
SDADC_ConfParamTypeDef ConfParamStruct = {0};
if (ECG_channel_max < 0xFFFF)
{
if (ECG_channel_max-ECG_channel_min < 0x4FFF) // about 1/3 of full scale
{
ConfParamStruct.Gain += 1;
}
}
if (ECG_channel_max >= 0xF000)
{
ConfParamStruct.Gain -= 1;
}
if (ECG_channel_max-ECG_channel_min >= 0xA000) // about 2/3 of full scale
{
ConfParamStruct.Gain -= 1;
}
if (HAL_SDADC_PrepareChannelConfig(&hsdadc1, SDADC_CONF_INDEX_0, &ConfParamStruct) != HAL_OK)
{
Error_Handler();
}
if (HAL_SDADC_AssociateChannelConfig(&hsdadc1, SDADC_CHANNEL_6, SDADC_CONF_INDEX_0) != HAL_OK)
{
Error_Handler();
}
// reset the min and max values
ECG_channel_max = 0;
ECG_channel_min = 0xFFFF;
}
The thing is, I want to use something like this, but 'ConfParamStruct.Gain' cannot be incremented as seen above. I could use alot of if-statements to change the gain (say from SDADC_GAIN_4 to SDADC_GAIN_8), but I wanted a more elegant solution.
Does anyone have a good idea on how to accomplish this? Thank you in advance!
