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authorMarti Bolivar <mbolivar@leaflabs.com>2011-05-09 16:43:27 -0400
committerMarti Bolivar <mbolivar@leaflabs.com>2011-05-09 16:49:08 -0400
commit19ea6ba4ea3f1ecb9830cf4d3e1366513f4f96e3 (patch)
treea43f7e0fb3650ca54f245b750a078a0e8c356504 /docs/source/lang/api/analogread.rst
parent868fb1c273e562a1140abfa948022c9d4f55bccf (diff)
parent1e2e177f6dae62e040c674b617744c73be187062 (diff)
downloadlibrambutan-19ea6ba4ea3f1ecb9830cf4d3e1366513f4f96e3.tar.gz
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Merge branch 'refactor'
This merges the libmaple refactor work into master. The contents of libmaple proper (/libmaple/) are almost completely incompatible with previous APIs in master. See /docs/source/libmaple/overview.rst for more information on the new design. Wirish incompatibilities are limited to the HardwareTimer class; however, there are several new deprecations, most likely to be removed in 0.1.0.
Diffstat (limited to 'docs/source/lang/api/analogread.rst')
-rw-r--r--docs/source/lang/api/analogread.rst78
1 files changed, 39 insertions, 39 deletions
diff --git a/docs/source/lang/api/analogread.rst b/docs/source/lang/api/analogread.rst
index 35c6fbc..6665a94 100644
--- a/docs/source/lang/api/analogread.rst
+++ b/docs/source/lang/api/analogread.rst
@@ -20,53 +20,56 @@ Library Documentation
Discussion
----------
-Reads the value from the specified analog pin. The Maple board
-contains a 16-channel, 12-bit analog to digital converter. This means
-that it will map input voltages between 0 and 3.3 volts into integer
-values between 0 and 4095. This yields a resolution between readings
-of 3.3V / 4096 units, or 0.8 millivolts. However, a number of factors
+Reads the value from the specified analog pin. The Maple boards
+contain 16-channel, 12-bit analog to digital converters. This means
+that a converter will map input voltages between 0 and 3.3 volts into
+integer values between 0 and 4095. However, a number of factors
interfere with getting full accuracy and precision. For more
information, see :ref:`adc`.
Before calling analogRead() on a pin, that pin must first be
-configured for analog input, using :ref:`lang-pinMode` (you only
-have to do this once, so it's usually done in :ref:`lang-setup`\ ).
+configured for analog input, using :ref:`lang-pinMode`. You only have
+to do this once, so it's usually done in :ref:`lang-setup`\ .
Parameter Discussion
--------------------
The pin parameter is the number of the analog input pin to read from.
-Header pins on the Maple with ADC functionality (marked as "AIN" on
-the silkscreen) are:
-
- 0, 1, 2, 3, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 27, 28
-
-Note that pins 3, 27, and 28 are not marked AIN on the silkscreen
-for Maple revisions through Rev 5, however, they **do work** as
-analog input pins.
+The pins which support analog to digital conversion have ``AIN``
+listed underneath their number on your board's silkscreen. These pin
+numbers are available to your program in the :ref:`boardADCPins
+<lang-board-values-adc-pins>` board-specific array. The number of
+pins which are capable of analog to digital conversion on your board
+is given by the ``BOARD_NR_ADC_PINS`` constant. These values are
+documented for each board in the :ref:`Board Hardware Documentation
+<index-boards>` pages.
+
+.. note:: Pin 3 is not marked ``AIN`` on the silkscreen for Maple
+ revisions through Rev 5; however **it does work** as an analog
+ input pin.
Note
----
If the analog input pin is not connected to anything, the value
-returned by analogRead() will fluctuate based on a number of factors
-(e.g. the values of the other analog inputs, how close your hand is to
-the board, etc.) in a seemingly random way.
-
+returned by ``analogRead()`` will fluctuate due to a number of reasons
+(like the values of the other analog inputs, how close your hand is to
+the board, etc.) in a "random" way.
Example
-------
- ::
+::
+ int analogPin = 3; // Potentiometer wiper (middle terminal) connected
+ // to analog pin 3. outside leads to ground and +3.3V.
+ // You may have to change this value if your board
+ // cannot perform ADC conversion on pin 3.
- int analogPin = 3; // potentiometer wiper (middle terminal) connected
- // to analog pin 3. outside leads to ground and +3.3V
int val = 0; // variable to store the value read
void setup() {
pinMode(analogPin, INPUT_ANALOG); // set up pin for analog input
- SerialUSB.begin(); // set up usb virtual COM port
}
void loop() {
@@ -75,7 +78,6 @@ Example
// a serial monitor
}
-
Arduino Compatibility
---------------------
@@ -97,23 +99,21 @@ shift <lang-bitshift>` the value of a Maple readout by 2, like so::
// be aware that you're losing a lot of precision if you do this
int adc_reading = analogRead(pin) >> 2;
+.. FIXME [0.1.0] Mention that Native can do analogReference()
+
On the Arduino, the input range and resolution can be changed using
-their implementation of `analogReference()
-<http://arduino.cc/en/Reference/AnalogReference>`_\ . Because of the
-way its hardware (as of Rev 5) was designed, it's not possible to
-implement analogReference on the Maple, so this function doesn't
-exist. If your inputs lie in a different voltage range than 0V--3.3V,
-you'll need to bring them into that range before using analogRead.
-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, opamps and other powered components can also be used if
-greater precision is required.
-
-See also
+the `analogReference()
+<http://arduino.cc/en/Reference/AnalogReference>`_ function. Because
+of hardware restrictions, this function is not available on the Maple
+and Maple RET6 Edition. If your inputs lie in a different voltage
+range than 0V--3.3V, you'll need to bring them into that range before
+using ``analogRead()``. See the :ref:`ADC reference <adc-range>` for
+more information.
+
+See Also
--------
-- :ref:`ADC note <adc>`
+- :ref:`ADC tutorial <adc>`
- `(Arduino) Tutorial: Analog Input Pins <http://arduino.cc/en/Tutorial/AnalogInputPins>`_
-.. include:: cc-attribution.txt
+.. include:: /arduino-cc-attribution.txt