I am using a Nucleo-32 board to sample 2 ADC channels. I am using the Cube MX and Cube L4 libraries. I am sampling CH1 for a fixed number of samples using DMA. I am using the callback HAL_ADC_ConvCpltCallback to change the ADC configuration to sample CH2. Here is the code:
void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
//void ADC_DMAConvCplt(ADC_HandleTypeDef* hadc)
{
static uint16_t i;
static float * aInd;
static float * aRes;
static uint32_t bChg;
//reconfigure to read ADC CH2
//Begin with Ch 1 (Reference). Note: Callback will switch to Ch 2
HAL_ADC_Stop_DMA(&hadc1);
HAL_ADC_ConfigChannel(&hadc1, &SenConfig);
HAL_ADC_Start_DMA(&hadc1,(uint32_t *)aADCxConvertedData, ADC_PERIOD_SAMPLE_CNT);
...
}
The desired configuration is preset in SenConfig so it is not computed here and thus increases the speed. I basically need to change the ADC channel number, all other parameters are the same. I don't know if there is a better way that I could configure DMA to reconfigure the ADC? If you have any idea then I would be interested.
I need to compare CH1 and 2 data to a known sine wave. The number of samples is chosen so that the first sample of CH1 can be compared to the first sample of CH2. So I need to know if I miss a sample so that I can compensate for that in my comparison algorithm. The problem I am having is that I observe the very first sample of CH2 data is containing what looks like a continuation of sampling CH1. I'm guessing that using this callback may mean one or more ADC conversions + DMA transfers has occured before I can make this switch. After the first sample it looks like CH2 data. Also, from the data it looks like maybe there is a loss of one sample as well. Possibly stopping and starting the DMA?
If anyone has any thoughts to help me understand why my data looks like this I appreciate it. Also, if you have a better way to perform the switching to avoid the problems altogther that would be great. Thanks so much.
Note: I am using the STM32L432 processor which has only one ADC. So Dual Regular Simultaneous mode for the ADC is not possible with one ADC. I am not using the Multichannel (scan) mode as I am not really sure how far offset the CH2 scan would be from CH1 and how to compare that to my reference sine wave. So I am using Single Channel Discontinuous converstion mode triggered by DMA and attempting to switch ADC channels.
