I use two ADCs for data acquisition. No matter in independent mode or synchronous mode, PA0 (channel 0) will have burr-like signals, and PA1 (channel 1) will have a level of about 1.7V (half of the 3.3V power supply). Both pins are suspended, and the normal 0V is when the AD conversion is not started. And whether using ADC1 or ADC2, the situation is the same. Has any expert encountered this problem?
Correction: If PA0, PA1, and PA2 are all left floating, the situation is the same. When the ADC is started, the pin will have about 1/2 of the supply voltage. The previous situation of PA0 should be caused by the pull-down resistor. The situation is the same now. Is it a configuration problem? Has anyone encountered this?
To prevent any influence, I left those pins floating. As long as the ADC is working, there will be a voltage of about 1.7V. I tried the examples that come with the library, using channel 14, and the situation is the same. My device is STM32F103RBT6, and I don't know where the problem is.
I tested it again and it appears after the soft start conversion. It should appear during the conversion. If you choose the single conversion mode, it will return to 0V after the conversion. If you use an infinite loop to ADC_SoftwareStartConvCmd, it will always be at that level. Is there something wrong with the settings? The situation is the same when using the example program.
Haha, this is a newbie's question. My input is based on resistor voltage division. I checked the relevant information and suspected that the input impedance is too large.
I didn't really pay attention to this problem when using AVR AD before, but I found that using STM32 ADC is more troublesome. I tried to input the measurement signal directly without voltage division before, but it directly affected the amplitude of the measurement signal. Do I really need to add a voltage follower? I am still debugging to see if there are other solutions.
I have already used ADC_SampleTime_239Cycles5. According to the information I found, the input impedance can reach 350K ohms. It still has problems. It is really not easy to use.
There were many problems when I used it for the first time. I thought it was easy to use and there was no need to pay attention to many things. It seems that the analog input of STM32 has many requirements. Now I have made a large number of boards and it is almost unusable. Fortunately, AD acquisition is not the main function. Before, two 1K resistors were used to divide the voltage to measure the signal. Now it is changed to 51K, which has little effect on the original signal. (When it is 1K, the original 2V signal is increased to 1.3V when connected to STM32). It seems that I can only add a voltage follower next time.
Correction: If PA0, PA1, and PA2 are all left floating, the situation is the same. When the ADC is started, the pin will have about 1/2 of the supply voltage. The previous situation of PA0 should be caused by the pull-down resistor. The situation is the same now. Is it a configuration problem? Has anyone encountered this? ...
This is normal:
1) I actually saw a similar situation when using STM32 AD
2) ST seems to have explained this issue, and I remember that this situation is related to the structure of AD.
But then again, in actual use, AD input is generally not left floating.
There were many problems when I used it for the first time. I thought it was easy to use and there was no need to pay attention to many things. It seems that the analog input of STM32 has many requirements. Now I have made a large number of boards, and they are almost unusable. Fortunately, AD acquisition is not the main function. Before, two 1K resistors were used to divide the voltage to measure the signal, and now it has been changed to 51K, which has changed the original...
The AD of STM32 is actually not difficult to use. For example, one end of a 10k potentiometer is connected to the power supply voltage (the other end is grounded). In this case, using the AD of STM32 to measure the voltage divider output of the potentiometer is still very accurate.
The power supply is very accurate, which is mainly related to the impedance and output current of the measurement signal output by the front stage. I did not find any problems when debugging the development board, so I did not look closely at the internal structure. I compared the ADC structure of AVR and STM32. There is an amplifier inside AVR, because this makes it possible for AVR to have no problems when measuring the level signal in the same circuit voltage division, but STM32 has similar problems. So when using ADC in the future, you should pay more attention to impedance and other issues. The safer method is of course to add a voltage follower.
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