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diff --git a/source/adc.rst b/source/adc.rst index 18c54ab..2cf9018 100644 --- a/source/adc.rst +++ b/source/adc.rst @@ -4,33 +4,59 @@ 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. +Analog to digital conversion is the process of reading a physical +voltage as a number. Maple can convert voltages between 0 and 3.3V to +numbers between 0 and 4095. .. contents:: Contents :local: +ADC On Maple +------------ + +Doing analog-to-digital conversion on the Maple is simple. +:ref:`Maple IDE <ide>` contains a basic example. To see it, choose +Analog > AnalogInSerial from the :ref:`examples menu <ide-examples>`. + +In order to set up your board for conversion, first connect the wire +(potentiometer, etc.) with the voltage you want to measure to a +:ref:`pin <gpio>` which can perform ADC. Each pin which can do ADC +has "AIN" (or "ain") written next to the the pin number. Then, as in +the example program, set the chosen pin's :ref:`pin mode +<lang-pinmode>` to ``INPUT_ANALOG`` by calling ``pinMode(<your_pin>, +INPUT_ANALOG)``. You will usually do this in your :ref:`lang-setup` +function. Now you can use :ref:`lang-analogread` to perform an ADC +reading. + +.. _adc-function-reference: + +Function Reference +------------------ + +* :ref:`lang-analogread` +* :ref:`lang-pinmode` + .. _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. +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. In theory, this means that a change in +voltage of about 1 millivolt should change the numeric voltage reading +by 1. In reality, however, a number of issues introduce noise and +bias into this reading, and a number of techniques must be used to get +good precision and accuracy. + +In order to allow for good readings, LeafLabs has tried to isolate at +least some of each board's ADC pins and traces from strong noise +sources. However, there are always trade-offs between noise, +additional functionality, cost, and package size. More information on +these isolated pins is available in each board's hardware +documentation: -More information on these isolated pins is available in each board's -hardware documentation: +.. FIXME [0.0.12, Maple Native] * :ref:`Maple <maple-adc-bank>` * :ref:`Maple RET6 Edition <maple-ret6-adc-bank>` @@ -63,14 +89,6 @@ are `resistor dividers <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 |