STM32H743 ADC Regular and injected conversions oversampling problems

[MSard]

Hello,

in my project I connected 6 channels to ADC3; then i set up:

• A single mode regular sequence to read 5 of them using DMA; start of sequence is given by software inside a periodic task
• An injected sequence for the 6th channel to trigger a conversion when needed

I want to use oversampling for both regular and injected conversions (the RM states that this is possible).

Setup of ADC 3 is the following:

static ADC_InitTypeDef initADC3 =    		//Monitoring ADC
{ 
ADC_CLOCK_ASYNC_DIV4,  //ClockPrescaler
ADC_RESOLUTION_16B,	//Resolution
ADC_SCAN_ENABLE, 	 	//Configure the sequencer of ADC groups regular and injected.
ADC_EOC_SEQ_CONV,	//Specify which EOC (End Of Conversion) 
DISABLE, 				//Low power Auto Delay
DISABLE,			       //Conversion is performed in single mode (one conversion)
5, 						//Number of ranks converted within the regular group sequencer.
DISABLE, 				//Complete-sequence/Discontinuous-sequence
1, 	 					//Specifies the number of discontinuous - Discarded here
ADC_SOFTWARE_START,	//Event source used to trigger ADC group regular conversion start.
ADC_EXTERNALTRIGCONVEDGE_NONE,
ADC_CONVERSIONDATA_DMA_CIRCULAR, 	
ADC_OVR_DATA_OVERWRITTEN,//Select the behavior in case of overrun
ADC_LEFTBITSHIFT_NONE,
ENABLE,    			      // oversampling feature is enabled
{ //Oversampling parameters
3,                                           //Ratio
ADC_RIGHTBITSHIFT_2,    // Right-shift 2 bit (/4) -> Sum of 4 val, then /4 -> Average
ADC_TRIGGEREDMODE_SINGLE_TRIGGER,	
ADC_REGOVERSAMPLING_RESUMED_MODE	
}							 
};

Setup of regular channels is the following:

static ADC_ChannelConfTypeDef ADC3_ChannelConf[] =
{ 
//Sens 12V_PWR
	{ ADC_CHANNEL_7, ADC_REGULAR_RANK_1, ADC_SAMPLETIME_8CYCLES_5, ADC_SINGLE_ENDED, ADC_OFFSET_NONE, 0, DISABLE, DISABLE },  
//Sens_3v3A							 
	{ ADC_CHANNEL_8, ADC_REGULAR_RANK_2, ADC_SAMPLETIME_8CYCLES_5, ADC_SINGLE_ENDED, ADC_OFFSET_NONE, 0, DISABLE, DISABLE },
//Sens_15V
	{ ADC_CHANNEL_10, ADC_REGULAR_RANK_3, ADC_SAMPLETIME_8CYCLES_5, ADC_SINGLE_ENDED, ADC_OFFSET_NONE, 0, DISABLE, DISABLE },  
//Sens_n15V
	{ ADC_CHANNEL_11, ADC_REGULAR_RANK_4, ADC_SAMPLETIME_8CYCLES_5, ADC_SINGLE_ENDED, ADC_OFFSET_NONE, 0, DISABLE, DISABLE },
//Sens 5Va
	{ ADC_CHANNEL_12, ADC_REGULAR_RANK_5, ADC_SAMPLETIME_8CYCLES_5, ADC_SINGLE_ENDED, ADC_OFFSET_NONE, 0, DISABLE, DISABLE },  
};

And of the injected channel:

static ADC_InjectionConfTypeDef ADC3_JChannelConf[] = 
{ 
{
ADC_CHANNEL_2,			// Specifies the channel to configure into ADC group injected.
ADC_INJECTED_RANK_1,		// Specifies the rank in the ADC group injected sequencer.
ADC_SAMPLETIME_8CYCLES_5,	// Sampling time value to be set for the selected channel.
ADC_SINGLE_ENDED,			// Selection of single-ended or differential input.
ADC_OFFSET_NONE,			// Selects the offset number.
0,							// Offset to be subtracted from the raw converted data.
DISABLE,					// Specifies whether the 1 bit Right-shift feature is used or not.
DISABLE,					// Signed saturation feature not used		ADC_LEFTBITSHIFT_NONE,	// Configures the left shifting applied to the final result
1,							// Number of ranks that will be converted within the ADC group injected sequencer.
DISABLE,					// Complete-sequence/Discontinuous-sequence
DISABLE,					// Disables injected automatic conversion after regular one
DISABLE,					// Specifies whether the context queue feature is enabled.
ADC_INJECTED_SOFTWARE_START, // Trigger the conversion start of injected group.
ADC_EXTERNALTRIGINJECCONV_EDGE_NONE, 
ENABLE,					// oversampling feature is enabled
{ //Oversampling parameters
3, 						// Ratio
ADC_RIGHTBITSHIFT_2	// Right-shift 2 bit (/4) -> Sum of 4 val, then /4 -> Average
}
}		
};

At this stage of debugging I never call the ADC_PerformInjectedConversion() function, so I am sure that only regular sequences are performed.

The problem is :

• If overasample is enabled for both regular channels and injected channel (as shown above), conversion of regular channels is wrong
• If oversample is enabled just for regualr channels and disabled for injected channel, conversion of regular channel is OK
• if oversample is enabled only for injected channel and disabled for regular channels, conversion of regular channel is wrong

May it be just a configuration problem ?

Any suggestions ?

Thank you