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diff --git a/watch-library/hal/documentation/adc_sync.rst b/watch-library/hal/documentation/adc_sync.rst new file mode 100644 index 00000000..d189565a --- /dev/null +++ b/watch-library/hal/documentation/adc_sync.rst @@ -0,0 +1,74 @@ +====================== +ADC Synchronous driver +====================== + +An ADC (Analog-to-Digital Converter) converts analog signals to digital values. +A reference signal with a known voltage level is quantified into equally +sized chunks, each representing a digital value from 0 to the highest number +possible with the bit resolution supported by the ADC. The input voltage +measured by the ADC is compared against these chunks and the chunk with the +closest voltage level defines the digital value that can be used to represent +the analog input voltage level. + +Usually an ADC can operate in either differential or single-ended mode. +In differential mode two signals (V+ and V-) are compared against each other +and the resulting digital value represents the relative voltage level between +V+ and V-. This means that if the input voltage level on V+ is lower than on +V- the digital value is negative, which also means that in differential +mode one bit is lost to the sign. In single-ended mode only V+ is compared +against the reference voltage, and the resulting digital value can only be +positive, but the full bit-range of the ADC can be used. + +Usually multiple resolutions are supported by the ADC, lower resolution can +reduce the conversion time, but lose accuracy. + +Some ADCs has a gain stage on the input lines which can be used to increase the +dynamic range. The default gain value is usually x1, which means that the +conversion range is from 0V to the reference voltage. +Applications can change the gain stage, to increase or reduce the conversion +range. + +The window mode allows the conversion result to be compared to a set of +predefined threshold values. Applications can use callback function to monitor +if the conversion result exceeds predefined threshold value. + +Usually multiple reference voltages are supported by the ADC, both internal and +external with difference voltage levels. The reference voltage have an impact +on the accuracy, and should be selected to cover the full range of the analog +input signal and never less than the expected maximum input voltage. + +There are two conversion modes supported by ADC, single shot and free running. +In single shot mode the ADC only make one conversion when triggered by the +application, in free running mode it continues to make conversion from it +is triggered until it is stopped by the application. When window monitoring, +the ADC should be set to free running mode. + +Features +-------- +* Initialization and de-initialization +* Support multiple Conversion Mode, Single or Free run +* Start ADC Conversion +* Read Conversion Result + +Applications +------------ +* Measurement of internal sensor. E.g., MCU internal temperature sensor value. +* Measurement of external sensor. E.g., Temperature, humidity sensor value. +* Sampling and measurement of a signal. E.g., sinusoidal wave, square wave. + +Dependencies +------------ +* ADC hardware + +Concurrency +----------- +N/A + +Limitations +----------- +N/A + +Knows issues and workarounds +---------------------------- +N/A + |