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diff --git a/source/faq.rst b/source/faq.rst deleted file mode 100644 index bd155ae..0000000 --- a/source/faq.rst +++ /dev/null @@ -1,115 +0,0 @@ -.. highlight:: cpp - -.. _faq: - -================================== - Frequently Asked Questions (FAQ) -================================== - -.. contents:: Contents - :local: - -.. _faq-atoi: - -Can I use ``atoi()``, ``strol()``, etc.? ----------------------------------------- - -Just ``#include <stdlib.h>``. See :ref:`arm-gcc-libc` for more -information. - -.. _faq-dynamic-memory: - -Can I use ``malloc()``/``new``? -------------------------------- - -For ``malloc()``, just ``#include <stdlib.h>``, and everything should -work fine. Be careful, though! This isn't like C programming on a -PC. You're on the bare metal, and probably shouldn't be using dynamic -memory unless you know what you're doing. - -``new`` should work out of the box (the warning about knowing what -you're doing applies here as well). If you find that ``new`` (or -``new[]``, ``delete``, etc.) is broken in some way, that's a bug; -please let us know in the `forum`_. - -Some information on the heap: on boards with an external SRAM chip -(like Maple Native), the heap is located on external SRAM by default. -For other boards, the heap is located immediately after ``.bss``, and -grows towards the stack. (In all cases, statically allocated -variables and the stack are located on internal SRAM, for performance -reasons). - -.. _faq-flash-tables: - -How do I replace ``PROGMEM``/put data into Flash? -------------------------------------------------- - -See :ref:`this note <arm-gcc-attribute-flash>`. - -How do I write to a pin at high speed? --------------------------------------- - -Sometimes, :ref:`lang-digitalwrite` just isn't fast enough. If that's -your situation, you should first try using fast GPIO writes using the -low-level :ref:`libmaple-gpio` interface. This FAQ entry explains -how. - -You'll need to look up the :ref:`GPIO port and bit <gpio-ports>` which -correspond to the pin you want to write to. If you don't know what -that means, don't worry. We'll go through an example here. - -Let's say you want to write to pin 4 on the Maple. In order to find -out the port and bit number, take look at the Maple's :ref:`master pin -map <maple-pin-map-master>` next to "D4". You'll see that in the -"GPIO" column, there's "PB5". That's short for "**P**\ ort **B**, bit -**5**". So the GPIO port is "B", and the bit is "5". (If you're not -on the Maple, you can find your board's pin map :ref:`from here -<gpio-pin-maps>`). - -That's all you need to know. Now you can use the function -``gpio_write_bit()`` to quickly write to the pin. The way you call it -is by writing ``gpio_write_bit(GPIO<port>, <bit>, HIGH/LOW)``, where -``<port>`` is the GPIO port, ``<bit>`` is the bit, and ``HIGH`` or -``LOW`` is the level you want to write to the pin. Here's an example -program which writes pin 4 (GPIOB, bit 5) ``HIGH`` and then ``LOW`` -several times in a row each time it :ref:`lang-loop`\ s:: - - /* - Fast pin writing example, for Maple. - - This example works for pin 4 (PB5 on Maple). If you want to - use another pin (or are on another board), just change PIN, - PIN_PORT, and PIN_BIT as described above. - */ - - #define PIN 4 - #define PIN_PORT GPIOB - #define PIN_BIT 5 - - void setup() { - pinMode(PIN, OUTPUT); - } - - void loop() { - gpio_write_bit(PIN_PORT, PIN_BIT, HIGH); - gpio_write_bit(PIN_PORT, PIN_BIT, LOW); - gpio_write_bit(PIN_PORT, PIN_BIT, HIGH); - gpio_write_bit(PIN_PORT, PIN_BIT, LOW); - } - -Now, if you've already tried this and you still can't get enough -speed, there are some threads on the `forum`_ which might help you -squeeze a little extra out of your board. First, a `general summary -<http://forums.leaflabs.com/topic.php?id=860>`_ of other things to -try, with measurements of the speed you'll get. Next, a thread -featuring a `detailed discussion on pin capability -<http://forums.leaflabs.com/topic.php?id=774>`_, with a focus on -writes. And finally, `another thread -<http://forums.leaflabs.com/topic.php?id=895>`_ on the subject which -summarizes a variety of other threads on doing I/O quickly. - -Can I use Maple without Maple IDE? ----------------------------------- - -Yes. See :ref:`unix-toolchain` for the details. - |