Several issues to note when using STM32 ADC

1. Vdda is not powered or is not powered normally. There are many STM32 series, and this parameter cannot be generalized. For details, please refer to the data manual of each chip.

2. The sampling resistor value is not appropriate and does not match the sampling time. It is often manifested as too large input resistance and short configured sampling time. In actual design, you can refer to the relevant circuits of the official STM32 series evaluation boards. In addition, you can refer to the official ST application note AN2834. For other application notes on ADC applications, you can go to WWW.STMCU.COM.CN and search for ADC.

3. It takes a while for the ADC to be stable after it is powered on, that is, Tstab. This parameter is introduced in the data sheet. Pay special attention to this time when using register operations. In addition, it should be noted that powering on the ADC peripheral, enabling the ADC function, starting the ADC conversion, and actual AD conversion are different actions and different time points.

4. The input signal amplitude exceeds the ADC reference voltage range, resulting in data errors in the conversion result.
5. The fluctuation of the chip power supply, especially the fluctuation of VREF and external interference will cause abnormal ADC conversion values.
6. When using injection trigger conversion, the time interval of the trigger event must be greater than the conversion time required for the injection conversion sequence. For example, if there are two injection channels with a conversion time of 28 ADCLK, then the interval of the trigger event must be greater than 28 ADCLK, such as 29, 30 ADCLK, etc.
7. Most STM32 ADC modules need to be calibrated before use. Calibration must be completed before starting AD conversion. In principle, it is enough to calibrate the ADC peripheral once after powering on, but when the reference voltage fluctuates greatly and the temperature changes drastically, it needs to be calibrated again.
8. It is recommended to enable the DMA function of the ADC after ADC calibration. In other words, do not enable the DMA function of the ADC before calibrating the ADC. Especially when it comes to multi-channel ADC DMA transmission, pay attention to this order.
9. If ADC DMA transmission is used, DMA must be configured and enabled when starting AD conversion.
10. When using the internal SENSOR ADC channels, please note that it takes time for these channels to be turned on and stabilized, just like turning on the ADC module; for the AD sampling time of these specific sensor channels, the manual often has relevant parameters clearly stated, please refer to it. For example, the sampling time of the internal temperature sensor channel is recommended to be 17us.
11. The modification of the ADC channel sequence should be performed in the ADC stop state.
12. In multi-channel ADC DMA transmission, abnormal conditions often occur due to inconsistency between buffer data type and source data type. This is mainly caused by inconsistent data width.
13. When an external signal is selected as the trigger signal for injection conversion, only its rising edge is valid.

The above are just reminders to start a new round of research. Pay more attention when designing applications, especially the 7th, 8th, 9th, and 12th four reminders. The ADC peripherals of STM32 are not exactly the same between different series, especially when it involves multiple ADC modules to cooperate with sampling conversion, it is still quite complicated. At any time, don't forget to check the STM32 English reference manual and data sheet.