diff options
Diffstat (limited to 'source/lang/api')
| -rw-r--r-- | source/lang/api/constants.rst | 8 | ||||
| -rw-r--r-- | source/lang/api/shiftout.rst | 99 |
2 files changed, 99 insertions, 8 deletions
diff --git a/source/lang/api/constants.rst b/source/lang/api/constants.rst index 72738b8..2e968e7 100644 --- a/source/lang/api/constants.rst +++ b/source/lang/api/constants.rst @@ -61,14 +61,6 @@ pin is configured as an ``INPUT`` (using :ref:`pinMode() <lang-digitalread>`, the microcontroller will report ``HIGH`` if a voltage of 3 volts or more is present at the pin. -.. TODO? Following seems false; check it out sometime, leave out for now: - -.. A pin may also be configured as an ``INPUT`` with ``pinMode()``, and -.. subsequently made ``HIGH`` with :ref:`digitalWrite() -.. <lang-digitalwrite>`, this will set the internal pullup resistors, -.. which will *steer* the input pin to a HIGH reading unless it is pulled -.. LOW by external circuitry. - When a pin is configured to ``OUTPUT`` with pinMode, and set to ``HIGH`` with :ref:`digitalWrite() <lang-digitalwrite>`, the pin is at 3.3 volts. In this state it can *source* current, e.g. light an LED diff --git a/source/lang/api/shiftout.rst b/source/lang/api/shiftout.rst new file mode 100644 index 0000000..1d9ba12 --- /dev/null +++ b/source/lang/api/shiftout.rst @@ -0,0 +1,99 @@ +.. highlight:: cpp + +.. _lang-shiftout: + +shiftOut() +========== + +Shift out a byte of data, one bit at a time. + +.. contents:: Contents + :local: + +Library Documentation +--------------------- + +.. doxygenfunction:: shiftOut + +Discussion +---------- + +This is a software implementation. There is also a hardware :ref:`SPI +<spi>` library available which will be faster and consume less CPU +cycles than this function. + +Note that the ``dataPin`` and ``clockPin`` must already be configured +to :ref:`OUTPUT <lang-constants-output>` mode by a call to +:ref:`pinMode() <lang-pinmode>`. + +Also note that since shiftOut() outputs 1 byte (8 bits) at a time, it +requires multiple steps to output values larger than 255. + +Examples +-------- + +To use these examples, replace ``dataPin`` and ``clockPin`` with the +numbers of the pins you want to use:: + + /* MSBFIRST example */ + + uint16 data = 500; + // shift out high byte + shiftOut(dataPin, clockPin, MSBFIRST, (data >> 8)); + // shift out low byte + shiftOut(dataPin, clockPin, MSBFIRST, data); + + /* LSBFIRST serial */ + + data = 500; + // shift out low byte + shiftOut(dataPin, clockPin, LSBFIRST, data); + // shift out high byte + shiftOut(dataPin, clockPin, LSBFIRST, (data >> 8)); + +Arduino Tutorial Example +------------------------ + +This Arduino example runs unmodified on the Maple. For accompanying +circuit, see the `tutorial on controlling a 74HC595 shift register +<http://arduino.cc/en/Tutorial/ShiftOut>`_. + +:: + + //**************************************************************// + // Name : shiftOutCode, Hello World // + // Author : Carlyn Maw, Tom Igoe // + // Date : 25 Oct, 2006 // + // Version : 1.0 // + // Notes : Code for using a 74HC595 Shift Register // + // : to count from 0 to 255 // + //**************************************************************// + + // Pin connected to ST_CP of 74HC595 + int latchPin = 8; + // Pin connected to SH_CP of 74HC595 + int clockPin = 12; + // Pin connected to DS of 74HC595 + int dataPin = 11; + + void setup() { + // Set pins to output because they are addressed in the main loop + pinMode(latchPin, OUTPUT); + pinMode(clockPin, OUTPUT); + pinMode(dataPin, OUTPUT); + } + + void loop() { + // Count up routine + for (int j = 0; j < 256; j++) { + // Ground latchPin and hold low for as long as you are transmitting + digitalWrite(latchPin, LOW); + shiftOut(dataPin, clockPin, LSBFIRST, j); + // Return the latch pin high to signal chip that it + // no longer needs to listen for information + digitalWrite(latchPin, HIGH); + delay(1000); + } + } + +.. include:: /lang/cc-attribution.txt |