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diff --git a/docs/source/adc.rst b/docs/source/adc.rst deleted file mode 100644 index 18c54ab..0000000 --- a/docs/source/adc.rst +++ /dev/null @@ -1,88 +0,0 @@ -.. _adc: - -===== - ADC -===== - -Analog-Digital Conversion is the process of reading a physical voltage -as a number. The Maple has a large number of pins which are capable of -taking 12-bit ADC measurements, which means that voltages from 0 to -3.3V are read as numbers from 0 to 4095. This corresponds to a -theoretical sensitivity of just under 1 millivolt. In reality, a -number of factors introduce noise and bias into this reading, and a -number of techniques must be used to get good precision and accuracy. - -.. contents:: Contents - :local: - -.. _adc-noise-bias: - -Noise and Bias --------------- - -.. FIXME [0.0.12, Maple Native] - -The biggest issues with analog to digital conversion are noise and -bias. With the Maple line, we have tried to isolate the ADC pins and -traces from strong noise sources, but there are always trade-offs -between noise, additional functionality, cost, and package size. -We've tried to enable good analog performance by isolating as many ADC -pins as possible from digital noise on each board. - -More information on these isolated pins is available in each board's -hardware documentation: - -* :ref:`Maple <maple-adc-bank>` -* :ref:`Maple RET6 Edition <maple-ret6-adc-bank>` -* :ref:`Maple Mini <maple-mini-adc-bank>` - -.. :ref:`Maple Native <maple-native-adc-bank>` - -That said, there are a number of more general things you can do to try -to get good readings. If your input voltage changes relatively -slowly, a number of samples can be taken in succession and averaged -together, or the same voltage can even be sampled by multiple ADC pins -at the same time. - -Another important factor when taking a voltage reading is the -reference voltages that the sample is being compared against. For -Maple, the high reference is |vdda| and the low reference is ground. -This means that noise or fluctuations on either |vdda| or ground will -affect the measurement. It also means that the voltage you are trying -to sample must be between ground and 3.3 V. - -.. _adc-range: - -In the case of a variable reading, it is best if the voltage varies -over the entire range of 0 through 3.3 V; otherwise, only a fraction -of the sensitivity is being used. Some basic tools to accomplish this -are `resistor dividers -<http://en.wikipedia.org/wiki/Voltage_divider>`_ and `Zener diodes -<http://en.wikipedia.org/wiki/Voltage_source#Zener_voltage_source>`_\ -. However, `operational amplifiers -<http://en.wikipedia.org/wiki/Operational_amplifier>`_ and other -powered components can also be used if greater precision is required. - -.. _adc-function-reference: - -Function Reference ------------------- - -* :ref:`lang-analogread` -* :ref:`lang-pinmode` - -.. _adc-recommended-reading: - -Recommended Reading -------------------- - -* `Wikipedia: Analog-to-Digital Converter - <http://en.wikipedia.org/wiki/Analog-to-digital_converter>`_ -* `Arduino Analog Input Tutorial - <http://arduino.cc/en/Tutorial/AnalogInputPins>`_ -* ST documentation: - - * `Application Note on ADC Modes - <http://www.st.com/stonline/products/literature/an/16840.pdf>`_ (PDF) - * `Application Note on ADC Oversampling - <http://www.st.com/stonline/products/literature/an/14183.pdf>`_ (PDF) |