CC2640 ADC 外部基准电压如何连接

请教CC2640的ADC是否可以连接外部的基准电压？该连接到哪个引脚？

Loops：

用户手册有说明，只能用内部的。

Rex Kung：

回复 Loops:

 参考下面代码：

/*!*@briefSpecifies whether the internal reference of the ADC is sourced from the battery voltage or a fixed internal source.**- In practice, using the internal fixed voltage reference sets the upper range of the ADC to a fixed value. That value is 4.3V with*input scaling enabled and ~1.4785V with input scaling disabled. In this mode, the output is a function of the input voltage multiplied*by the resolution in alternatives (not bits) divided by the upper voltage range of the ADC. Output = Input (V) * 2^12 / (ADC range (V))**- Using VDDS as a reference scales the upper range of the ADC with the battery voltage. As the battery depletes and its voltage drops, so does*the range of the ADC. This is helpful when measuring signals that are generated relative to the battery voltage. In this mode, the output is*a function of the input voltage multiplied by the resolution in alternatives (not bits) divided by VDDS multiplied by a scaling factor derived*from the input scaling. Output = Input (V) * 2^12 / (VDDS (V) * Scaling factor), where the scaling factor is ~1.4785/4.3 for input scaling*disabled and 1 for input scaling enabled.**@noteThe actual reference values are slightly different for each device and are higher than the values specified above. This gain is saved in*the FCFG. The function ::ADC_convertRawToMicroVolts() must be used to derive actual voltage values. Do not attempt to compare raw values*between devices or derive a voltage from them yourself. The results of doing so will only be approximately correct.**@warningEven though the upper voltage range of the ADC is 4.3 volts in fixed mode with input scaling enabled, the input should never exceed*VDDS as per the data sheet.*/
typedef enum ADCCC26XX_Reference_Source {ADCCC26XX_FIXED_REFERENCE= AUXADC_REF_FIXED,ADCCC26XX_VDDS_REFERENCE= AUXADC_REF_VDDS_REL
} ADCCC26XX_Reference_Source;