Problem with ADC-Channel 16 (internal temperature) on STM32F207

[SRond]

Hi guys,

I have a problem with the internal temperature ADC-channel. I am trying to read a few analog values with ADC1. The ones I read from pins are perfectly fine but when I change the input voltage on PC13 (channel 13) this changes the value read on the internal temperature sensor (channel 16). The problem is not a wrong calculation of the temperature but just odd readings.

for Example:

2.5 Voltage on PC13 return 990 ADC-Registervalue and a temperature on the other channel of 20 to 100 degrees (wild movement)

5V ~ 1950            45 degrees

7,5V ~ 2911            54 degrees

10V ~ 3870            64  degrees          

2V ~ 800             211 degrees

1,75V ~ 705            200 degrees

The voltages are, of course, before the voltage divider and not at the respective pin but as you can see, the ADC-values behave accordingly to the change of voltage and the temperature value calculated from the ADC channel16 just behaves odd in my opinion. And I have no idea why.

Can anyone tell me if there is a connection between channel 16 and channel 13 or any other ADC-channel? I could not find anything on first look in the errata or the reference manual to ths STM32F207 but i may have overlooked it.

Init-Code: (pretty much the default code from cube ide)

/* USER CODE BEGIN ADC1_Init 0 */
 
  /* USER CODE END ADC1_Init 0 */
 
  LL_ADC_InitTypeDef ADC_InitStruct = {0};
  LL_ADC_REG_InitTypeDef ADC_REG_InitStruct = {0};
  LL_ADC_CommonInitTypeDef ADC_CommonInitStruct = {0};
 
  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};
 
  /* Peripheral clock enable */
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_ADC1);
  
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_GPIOC);
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_GPIOA);
  /**ADC1 GPIO Configuration  
  PC3   ------> ADC1_IN13
  PA3   ------> ADC1_IN3
  PA5   ------> ADC1_IN5
  PA6   ------> ADC1_IN6 
  */
  GPIO_InitStruct.Pin = ANALOG_IN_Pin;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ANALOG;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  LL_GPIO_Init(ANALOG_IN_GPIO_Port, &GPIO_InitStruct);
 
  GPIO_InitStruct.Pin = U_12V_Pin;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ANALOG;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  LL_GPIO_Init(U_12V_GPIO_Port, &GPIO_InitStruct);
 
  GPIO_InitStruct.Pin = U_5V_Pin;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ANALOG;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  LL_GPIO_Init(U_5V_GPIO_Port, &GPIO_InitStruct);
 
  GPIO_InitStruct.Pin = U_3V3_Pin;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ANALOG;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  LL_GPIO_Init(U_3V3_GPIO_Port, &GPIO_InitStruct);
 
  /* ADC1 DMA Init */
  
  /* ADC1 Init */
  LL_DMA_SetChannelSelection(DMA2, LL_DMA_STREAM_0, LL_DMA_CHANNEL_0);
 
  LL_DMA_SetDataTransferDirection(DMA2, LL_DMA_STREAM_0, LL_DMA_DIRECTION_PERIPH_TO_MEMORY);
 
  LL_DMA_SetStreamPriorityLevel(DMA2, LL_DMA_STREAM_0, LL_DMA_PRIORITY_HIGH);
 
  LL_DMA_SetMode(DMA2, LL_DMA_STREAM_0, LL_DMA_MODE_CIRCULAR);
 
  LL_DMA_SetPeriphIncMode(DMA2, LL_DMA_STREAM_0, LL_DMA_PERIPH_NOINCREMENT);
 
  LL_DMA_SetMemoryIncMode(DMA2, LL_DMA_STREAM_0, LL_DMA_MEMORY_INCREMENT);
 
  LL_DMA_SetPeriphSize(DMA2, LL_DMA_STREAM_0, LL_DMA_PDATAALIGN_HALFWORD);
 
  LL_DMA_SetMemorySize(DMA2, LL_DMA_STREAM_0, LL_DMA_MDATAALIGN_HALFWORD);
 
  LL_DMA_DisableFifoMode(DMA2, LL_DMA_STREAM_0);
 
  /* USER CODE BEGIN ADC1_Init 1 */
 
  /* USER CODE END ADC1_Init 1 */
  /** Common config 
  */
  ADC_InitStruct.Resolution = LL_ADC_RESOLUTION_12B;
  ADC_InitStruct.DataAlignment = LL_ADC_DATA_ALIGN_RIGHT;
  ADC_InitStruct.SequencersScanMode = LL_ADC_SEQ_SCAN_ENABLE;
  LL_ADC_Init(ADC1, &ADC_InitStruct);
  ADC_REG_InitStruct.TriggerSource = LL_ADC_REG_TRIG_SOFTWARE;
  ADC_REG_InitStruct.SequencerLength = LL_ADC_REG_SEQ_SCAN_ENABLE_12RANKS;
  ADC_REG_InitStruct.SequencerDiscont = LL_ADC_REG_SEQ_DISCONT_DISABLE;
  ADC_REG_InitStruct.ContinuousMode = LL_ADC_REG_CONV_CONTINUOUS;
  ADC_REG_InitStruct.DMATransfer = LL_ADC_REG_DMA_TRANSFER_UNLIMITED;
  LL_ADC_REG_Init(ADC1, &ADC_REG_InitStruct);
  LL_ADC_REG_SetFlagEndOfConversion(ADC1, LL_ADC_REG_FLAG_EOC_UNITARY_CONV);
  LL_ADC_DisableIT_EOCS(ADC1);
  ADC_CommonInitStruct.CommonClock = LL_ADC_CLOCK_SYNC_PCLK_DIV2;
  ADC_CommonInitStruct.Multimode = LL_ADC_MULTI_INDEPENDENT;
  LL_ADC_CommonInit(__LL_ADC_COMMON_INSTANCE(ADC1), &ADC_CommonInitStruct);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_1, LL_ADC_CHANNEL_3);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_3, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_2, LL_ADC_CHANNEL_3);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_3, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_3, LL_ADC_CHANNEL_5);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_5, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_4, LL_ADC_CHANNEL_5);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_5, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_5, LL_ADC_CHANNEL_6);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_6, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_6, LL_ADC_CHANNEL_6);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_6, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_7, LL_ADC_CHANNEL_13);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_13, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_8, LL_ADC_CHANNEL_13);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_13, LL_ADC_SAMPLINGTIME_3CYCLES);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_9, LL_ADC_CHANNEL_TEMPSENSOR);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_TEMPSENSOR, LL_ADC_SAMPLINGTIME_3CYCLES);
  LL_ADC_SetCommonPathInternalCh(__LL_ADC_COMMON_INSTANCE(ADC1), LL_ADC_PATH_INTERNAL_TEMPSENSOR);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_10, LL_ADC_CHANNEL_TEMPSENSOR);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_TEMPSENSOR, LL_ADC_SAMPLINGTIME_3CYCLES);
  LL_ADC_SetCommonPathInternalCh(__LL_ADC_COMMON_INSTANCE(ADC1), LL_ADC_PATH_INTERNAL_TEMPSENSOR);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_11, LL_ADC_CHANNEL_VREFINT);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_VREFINT, LL_ADC_SAMPLINGTIME_3CYCLES);
  LL_ADC_SetCommonPathInternalCh(__LL_ADC_COMMON_INSTANCE(ADC1), LL_ADC_PATH_INTERNAL_VREFINT);
  /** Configure Regular Channel 
  */
  LL_ADC_REG_SetSequencerRanks(ADC1, LL_ADC_REG_RANK_12, LL_ADC_CHANNEL_VREFINT);
  LL_ADC_SetChannelSamplingTime(ADC1, LL_ADC_CHANNEL_VREFINT, LL_ADC_SAMPLINGTIME_3CYCLES);
  LL_ADC_SetCommonPathInternalCh(__LL_ADC_COMMON_INSTANCE(ADC1), LL_ADC_PATH_INTERNAL_VREFINT);
  /* USER CODE BEGIN ADC1_Init 2 */
 
  ADC->CCR |= (0b11 << 20);//TSVREFE;

start code:

ADC_TypeDef *ADCx;
	DMA_TypeDef *DMAx;
	uint32_t CHx;
 
 
	// ADC1 uses DMA2 with channel 0
	// ADC1 samples 3 input Channels: internal temperature, VREF and IN8 channel
	ADCx = ADC1;
	DMAx = DMA2;
	CHx  = LL_DMA_STREAM_0;
 
	LL_ADC_Disable( ADCx );
	LL_ADC_DisableIT_EOCS( ADCx );
	LL_DMA_DisableStream( DMAx, CHx );
	LL_DMA_DisableIT_HT(DMAx, CHx);
	LL_DMA_DisableIT_TC(DMAx, CHx);
	LL_DMA_ConfigAddresses(DMAx, CHx, (uint32_t)&ADCx->DR, (uint32_t)&hwADC1_RawVal, LL_DMA_DIRECTION_PERIPH_TO_MEMORY );
	LL_DMA_SetDataLength(DMAx, CHx, (uint32_t)(sizeof(hwADC1_RawVal)/ sizeof(uint16_t) )  );
	LL_DMA_EnableStream( DMAx, CHx );
 
	LL_ADC_Enable( ADCx );
	LL_ADC_REG_StartConversionSWStart( ADCx );

Thanks in advance for any help or sugestions for a solution.

[TDK]

There's a 10us minimum sampling time for the temperature sensor per the datasheet. I doubt 3 cycles is enough unless your system clock is abnormally low.

I would guess the correlation with CH13 is simply because you're converting CH13 before the temperature sensor channel.

[SRond]

Thanks for the quick answer. I am going to try if the behavior changes with longer sample times for the temperature channel and a different sequence of converting