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Diffstat (limited to 'source/lang/api/analogread.rst')
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diff --git a/source/lang/api/analogread.rst b/source/lang/api/analogread.rst index c614aca..35c6fbc 100644 --- a/source/lang/api/analogread.rst +++ b/source/lang/api/analogread.rst @@ -32,11 +32,6 @@ 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`\ ). -It takes about 0.8 microseconds (.0000008 seconds) to read an analog -input, so the maximum sample rate using this function is approximately -1.3 million samples per second\ [#fsamp]_. - - Parameter Discussion -------------------- @@ -115,40 +110,10 @@ Some basic tools to accomplish this are `resistor dividers . However, opamps and other powered components can also be used if greater precision is required. -Finally, On the Arduino, it takes significantly longer to read analog -input: about 100 microseconds (0.0001 s), so the maximum reading rate -is 10,000 times a second. - - See also -------- - :ref:`ADC note <adc>` - `(Arduino) Tutorial: Analog Input Pins <http://arduino.cc/en/Tutorial/AnalogInputPins>`_ - -.. rubric:: Footnotes - -.. [#fsamp] This is based on the current configuration of a 55.5 cycle - sample time, at 72 MHz. However, the minimum sample time *possible* - is 1.5 cycles, leading to a theoretical maximum of approximately 48 - million samples per second (of course, doing anything with the - readings also consumes cycles, so this maximum can't be reached in - practice). - - See the `STM32 Reference Manual <full-manual>`_, ยงยง11.12.4--5 - (pp. 225--226), for more information on the low-level bit twiddling - currently necessary to change the sample time. For examples of how - the ADCs are configured in libmaple, see `adc.h - <http://github.com/leaflabs/libmaple/blob/master/libmaple/adc.h>`_ - and `adc.c - <http://github.com/leaflabs/libmaple/blob/master/libmaple/adc.c>`_\ - . Be aware that changing the sample time has important - consequences related to the impedance of the device connected to - the input pin. If you want to make changes, as a minimum, you - should first read ST's application notes on `ADC modes - <stm32-adc-modes>`_ and `ADC oversampling - <stm32-adc-oversampling>`_. - - .. include:: cc-attribution.txt |