ADC sampling problem of STM32F103

yunanxiang

ADC sampling problem of STM32F103 [Copy link]

How can I sample continuously?

My current method is: ADC12 samples the voltage and current of phase AB, ADC3 samples the voltage and current of phase C, CC2 and CC3 of TIM1 are used as triggers, DMA transmits the sampled data, calculates once after half of the transmission is completed, performs the next sampling during the calculation, and resamples the data to DMA after the full transmission is completed.

The problem is: the voltage of each phase will crosstalk into the current channel, that is, if only voltage is added without current, the current can be sampled!

The following is the ADC configuration program:

/* ADC1 configuration ---------------------------------------------------------*/
ADC_InitStructure.ADC_Mode = ADC_Mode_RegSimult;
ADC_InitStructure.ADC_ScanConvMode = ENABLE;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC2;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
ADC_InitStructure.ADC_NbrOfChannel = 2;
ADC_Init(ADC1, &ADC_InitStructure);


ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
ADC_Init(ADC2, &ADC_InitStructure);

ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T1_CC3;
ADC_Init(ADC3, &ADC_InitStructure);

/* ADC3 regular channel3 configuration, measure current in C*/
ADC_RegularChannelConfig(ADC3, ADC_Channel_1, 1, ADC_SampleTime_7Cycles5);
/* ADC3 regular channel10 Configuration, measure voltage in C*/
ADC_RegularChannelConfig(ADC3, ADC_Channel_10, 2, ADC_SampleTime_7Cycles5);

/* ADC2 regular channel6 configuration, measure current in B*/
ADC_RegularChannelConfig(ADC2, ADC_Channel_0, 1, ADC_SampleTime_7Cycles5);
/* ADC2 regular channel11 Configuration, measure voltage in B*/
ADC_RegularChannelConfig(ADC2, ADC_Channel_11, 2, ADC_SampleTime_7Cycles5);

/* ADC1 regular channel7 configuration, measure current in A*/
ADC_RegularChannelConfig(ADC1, ADC_Channel_13, 1, ADC_SampleTime_7Cycles5);
/* ADC1 regular channel12 Configuration, measure voltage in A*/
ADC_RegularChannelConfig(ADC1, ADC_Channel_12, 2, ADC_SampleTime_7Cycles5);

xgs_ht0033

                                 What does it mean to “sample current without adding current, only adding voltage”?

leafky

The ADC input is the output of the op amp. A 1K resistor was originally connected in series, but later it was replaced with 0ohm, but the result was the same.
The only difference between uninterrupted sampling and ordinary sampling is that data processing and other calculations are required while sampling.

keye200

                                 Using an oscilloscope, there is no crosstalk between the pins. The problem should be inside the chip.

aweyfan

That's right. If no voltage value is added, the buffer value after voltage sampling is around 2048. After adding current signal, there will be data in the voltage buffer that obviously deviates from the value of 2048. It is equivalent to having voltage. And this value increases with the increase of current.
If you only start ADC sampling and DMA transmission without doing anything else, this situation will not occur.

luoxinmjun520

" If you only start ADC sampling and DMA transfer and do nothing else, this situation will not occur. "

What does "do nothing else" mean? Did your "other things" change the contents of the DMA buffer, causing your wrong judgment?

123amy

                                 No current, only voltage?

NetCom

This is not a problem with the ADC, but a problem with the front-end analog channel. In addition, the results obtained by directly measuring crosstalk are generally very confusing. It depends on your measurement method. It is recommended to test the analog signal, that is, do not connect the actual signal, use an ideal signal source to simulate the input. If the result is normal, then your signal processing circuit is not done well. Signal conversion, isolation, reference potential, all of these need to be checked one by one.

ADC is actually a delicate thing.