USB-LED-Fader/firmware/pwm_channels.c

/**
 * \file pwm_channels.c
 * \brief Manages the values of the displayed channels.
 * \author Thomas Stegemann
 * \version $Id: pwm_channels.c,v 1.2 2006/09/29 22:30:03 rschaten Exp $
 *
 * License: See documentation.
 */

#include <stdlib.h>

#include "pwm_channels.h"
#include "pwm_timer.h"
#include "config_pwm_timer_impl.h"
#include "message_queue.h"

/** Structure to contain the state of one channel */
typedef struct S_pwm_Channels_ChannelBrightness {
    pwm_Channels_Bitfield field; /**< Bitfield resembling one channel */
    pwm_Timer_Cycles      cycle; /**< Number of on-cycles */
} pwm_Channels_ChannelBrightness;

/**
 * Initialize channels. Basically, only the PWM-timer is started.
 */
void pwm_Channels_init(void) {
    pwm_Timer_init();
}

/**
 * Clean up channels. Basically, the PWM-timer gets cleaned.
 */
void pwm_Channels_cleanup(void) {
    pwm_Timer_cleanup();
}

/**
 * Calculate the Channels_Message. Requires the channel-list to be sorted by
 * cycles.
 * \param channels Array of the channels.
 * \return Current message.
 */
static pwm_Channels_Message pwm_Channels_Message_get(pwm_Channels_ChannelBrightness channels[CHANNELS]) {
    int j; /* index of the current channel */
    pwm_Channels_StepCounter i= 0; /* index of the current step */
    pwm_Channels_Message message;
    /* first step: switch on all channels at cycle 0 */
    message.step[i].field = 0;
    for (j = 0; j < CHANNELS; j++) {
        message.step[i].field |= channels[j].field;
    }
    message.step[i].cycle= 0;

    for (j = 0; j < CHANNELS; j++) {
        if(channels[j].cycle == message.step[i].cycle) {
            /* if cycle for this channel is reached
               switch off channel in current step */
            message.step[i].field&= ~channels[j].field;
        } else {
            /* need another step for this channel:
               set end of the current step
               use copy of current step for next step
               and switch off this channel
            */
            message.step[i].cycle= channels[j].cycle;
            i++;
            message.step[i]= message.step[i-1];
            message.step[i].field&= ~channels[j].field;
        }
    }
    /* last step ends at pwm_Timer_Cycles_Max */
    message.step[i].cycle= pwm_Timer_Cycles_Max;
    return message;
}

/**
 * Calculate number of cycles from a brightness.
 * \param brightness The brightness.
 * \return The number of cycles.
 */
pwm_Timer_Cycles pwm_Channels_BrightnessToCycles(pwm_Channels_Brightness brightness) {
    return brightness * brightness;
}

/**
 * Compare the number of cycles in two channels. This is needed for the
 * qsort-call in pwm_Channels_show().
 * \param cmp1 First channel.
 * \param cmp2 Second channel.
 * \return A value <0 if cmp1 is smaller than cmp2, 0 if they are of the same
 * length and a value >0 if cmp1 is larger than cmp2.
 */
int pwm_Channels_CompareChannels(const void * cmp1, const void * cmp2) {
    return ((const pwm_Channels_ChannelBrightness*)cmp1)->cycle - ((const pwm_Channels_ChannelBrightness*)cmp2)->cycle;
}

/**
 * Writes the current pattern to the message-queue. The pattern is built from
 * the state of all channels.
 * \param channels Array with the channel-states.
 */
void pwm_Channels_show(pwm_Channels channels) {
    int i;
    pwm_Channels_Message message;
    pwm_Channels_ChannelBrightness channel_brightness[CHANNELS];
    for (i = 0; i < CHANNELS; i++) {
        channel_brightness[i].field = 1 << i; // 1 << i equals 2^i: the channel i, uses the bit i
        channel_brightness[i].cycle = pwm_Channels_BrightnessToCycles(channels.channel[i]);
    }

    qsort(channel_brightness, CHANNELS, sizeof(pwm_Channels_ChannelBrightness), pwm_Channels_CompareChannels);
    message= pwm_Channels_Message_get(channel_brightness);
    while(!messageQueue_write(message)) {
        pwm_Timer_idle();
    }
}