Element14 and Freescale's XL-STAR- S08 Development Board.

/**************************************************************************
* MAIN.C  
* Top level routines for XL_STAR board accelerometer demo
*
* Copyright (c) 2011 Freescale Semiconductor
* All Rights Reserved
*
*************************************************************************** 
*
* THIS SOFTWARE IS PROVIDED BY FREESCALE "AS IS" AND ANY EXPRESSED OR 
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  
* IN NO EVENT SHALL FREESCALE OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 
* THE POSSIBILITY OF SUCH DAMAGE.
*
**************************************************************************
* Comments:
*       Developed by MicroAPL Ltd on behalf of Freescale Semiconductor
*
* Revision History
*       06/01/11 SDM           Initial version
*       14/01/11 SDM (1.0.0)   First release
*
* HOW TO USE THE DEMO PROGRAM
* ---------------------------
* This program is designed to run on Freescale's XL_STAR board, and
* shows how to use the MMA8451Q accelerometer.
*
* When first powered on, the board will go into an 'orientation' demo mode.
* Try picking the board up and tipping it in different directions. You should
* see that the orange LEDs illuminate to indicate the direction of the tip
* and its magnitude.
*
* You can select between five different demos by repeatedly pressing button SW3,
* labelled 'Chan'. The current demo mode will be indicated by the green LEDs
* D6-D10. The available demo modes are:
*
*     Orient    - Try tipping the board and watch the orange LEDs indicate
*                 the direction and magnitude of tip
*
*     Shake     - Try flicking the board in a direction, either up or down,
*                 left or right, or forward or back, like striking a ball in
*                 a game of table tennis. The orange LEDs will point in 
*                 the direction of the initial flick, re-setting after a 
*                 couple of seconds.
*
*     Tap       - Hold the board loosely and tap it once with your finger;
*                 the LEDs will show a 'pulse' pattern.
*                 Tap twice in quick succession (double tap) to get a
*                 different animated pattern.
*
*     Freefall  - Drop the board from the height of a few centimetres or more. 
*                 The freefall event will be detected and displayed on the LEDs
*                 for a couple of seconds.
*
*     Transient - The orange LEDs will all illuminate if the board is moving,
*                 (strictly, if it is accelerating or decelerating) and turn  
*                 off after a short while if you stand still. 
*
* The accelerometer sensitivity can be changed by pressing button SW1, labelled 
* 'G sel'. This selects which multiple of normal gravity corresponds to a
* full-scale accelerometer reading. The options are 2g, 4g and 8g as indicated
* by the green LEDs D3-D5.
*
* The accelerometer can return 8-bit or 14-bit data to the main CPU. Applications 
* requiring more accuracy can use 14-bit data; otherwise it's faster to read 8-bit 
* data. You can select between the two options by pressing the SW2 button, labelled
* 'DataW'. The current selection is shown on the green LEDs D1-D2.
*
* Note that changing the sensitivity only affects the 'Orient' demo, because
* the other accelerometer functions used here don't depend on the sensitivity setting.
*
* Changing between 8-bit and 14-bit data also only affects the 'Orient' demo, but
* although the data width setting is honoured you probably won't notice the
* difference.
*
* When the accelerometer doesn't detect any interesting events for around 20 seconds,
* software will put the board into a power-saving mode. So that you can see this  
* happening, an 'X' pattern is displayed briefly before almost all the LEDs turn off.
*
* To wake the board up, just pick it. A '+' pattern is displayed briefly to indicate 
* that the board is awake again, and the current demo mode is then resumed.
*
*
* SOME NOTES ON PROGRAM STRUCTURE
* -------------------------------
* The following notes might be helpful for getting an understanding of the demo code.
*
* (1) On power-on reset, execution starts at label '_Startup' in Start08.c. This file
*     is common to many CodeWarrior HCS08 programs. Its main purpose is to set up the
*     runtime environment of the C program (stack, initialised data, etc). 
*
* (2) Control then transfers to our 'main' routine below. This sets up the hardware
*     and then enters an endless loop.
*
*     Within the loop, everything is interrupt driven. The microprocessor executes
*     the WAIT instruction in order to sleep when there's no new information from 
*     the accelerometer. It is woken from sleep by an interrupt, either from the
*     accelerometer or caused by a button press. The interrupt service routines
*     are 'accelerometer_isr' and 'button_press_isr.'
*
* (3) The accelerometer is configured differently each time a new demo mode is
*     selected. It would be possible to detect multiple events at once - e.g. single 
*     and double taps, orientation changes *and* freefall - by careful configuration.
*     To make it easier to understand the code, each demo mode only configures one
*     type of event.
*
* (4) After some seconds of inactivity the accelerometer will transition from
*     Wake to Sleep mode, and this will be indicated by an interrupt. The software
*     transfers control to the routine 'wait_for_movement' which reconfigures the
*     accelerometer to detect any movement and then puts both the accelerometer and
*     the board into low power modes.
* 
* (5) There are a number of routines with names like 'leds_circle' which are used
*     to display different patterns on the orange LEDs. These are all straightforward
*     except 'leds_show_tilt'. For added interest this uses the fact that the GPIO
*     pins driving the LEDs can also be reconfigured as outputs of the Timer/Pulse 
*     Width Modulator modules (TPMs). By driving the pins with a pulse-width modulated 
*     signal the brightness of the LEDs can be controlled.
*
* (6) This demo program is unusual in that it makes use of the ANSI C 'double' floating  
*     point data type, which is not typically the case for embedded software.
*     Floating point code is needed here to calculate tilt angles in the 'Orient' 
*     demo, and requires the use of a version of the ANSI library which includes maths
*     routines like 'cos' and 'atan2'. 
*
*     The library which includes floating point support is called 'ansifs.lib'. 
*     For most embedded applications you can make use of 'ansiis.lib', a simpler library 
*     which leads to slightly smaller code sizes. See the compiler documentation for 
*     more details.
* 
*/

#include           
#include "derivative.h"     
#include