In this paper, STM32F429IGT6 microcontroller as an example. STM32F429IGT6 ADC has three, each ADC has 12, 10, 8 and 6 Alternatively, each ADC has 16 external channels. There are two additional sources internal ADC channels and hanging on the V BAT ADC1. ADC has an independent mode, dual mode, and a triple mode, the AD conversion requirements for different modes are available almost all suitable. ADC is very powerful, we analyze the specific function of each part in the function block diagram.
Single ADC functional diagram is shown below:
Mastered the functional block diagram of the ADC, you can have an overall grasp of the ADC, when programming can be done as clear understanding of the chest, not little understood. Uses a block diagram to explain the way from left to right, with the ADC data acquisition, data conversion is probably the same direction, transmission of data.
Input voltage range
ADC input range: V REF- ≤ V IN ≤ V REF +. A V REF-, V REF +, V DDA, V SSA, four external pins determined.
We generally ground V SSA and V REF-, V REF + and the V DDA when connection 3V3 schematic design, to give the ADC input voltage range: 0 ~ 3.3V.
If we want the input voltage range is widened, to go to a higher voltage or a negative test positive voltage, we can add a voltage conditioning circuitry external to the converted voltage required to lift or down 0 ~ 3.3V, so ADC can be measured.
If the measured voltage exceeds 0 ~ 3.3V, a simple approach to: process the input voltage range (-10V ~ 10V)
Input channel
我们确定好 ADC输入电压之后，那么电压怎么输入到 ADC？这里我们引入通道的概念，STM32 的 ADC多达 19个通道，其中外部的 16个通道就是框图中的 ADCx_IN0、ADCx_IN1...ADCx_IN5。这 16 个通道对应着不同的 IO 口，具体是哪一个 IO 口可以从手册查询到。其中 ADC1/2/3 还有内部通道： ADC1的通道 ADC1_IN16 连接到内部的 VSS，通道 ADC1_IN17 连接到了内部参考电压 V REFINT 连接，通道 ADC1_IN18 连接到了芯片内部的温度传感器或者备用电源 V BAT 。ADC2 和 ADC3 的通道 16、17、18 全部连接到了内部的 VSS。
