ADC low level implementation for avr.

git-svn-id: https://src.develer.com/svnoss/bertos/trunk@1206 38d2e660-2303-0410-9eaa-f027e97ec537

diff --git a/app/triface/hw/hw_adc.c b/app/triface/hw/hw_adc.c
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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2003, 2004, 2006 Develer S.r.l. (http://www.develer.com/)
+ * Copyright 2000 Bernardo Innocenti <bernie@codewiz.org>
+ *
+ * -->
+ *
+ * \brief ADC: Analogic to Digital Converter
+ *
+ *
+ * \version $Id$
+ *
+ * \author Andrea Grandi <andrea@develer.com>
+ */
+
+#include "hw_adc.h"
+
+
+#include <cfg/macros.h>
+
+#include <drv/timer.h>
+
+#include <avr/io.h>
+
+/** Set the active AI channel */
+void adc_set_active_ain(int ai)
+{
+       /* If number of channels is <= 4 we use the first two MUX bits */
+       STATIC_ASSERT(ADC_CHANNEL_NUM <= 4);
+
+       ai &= BV(0) | BV(1);
+       ADMUX &= ~BV(MUX0);
+       ADMUX &= ~BV(MUX1);
+       ADMUX |= ai;
+}
+
+/** Initialize the ADC */
+void adc_init(void)
+{
+       /* Set analog IN as input */
+       DDRF &= ~(BV(PF0) | BV(PF1) | BV(PF2) | BV(PF3));
+
+       /* Disable pull-up */
+       PORTF &= ~(BV(PF0) | BV(PF1) | BV(PF2) | BV(PF3));
+
+       ENABLE_ADC;
+       adc_set_vref_avcc();
+       SET_AI_ADLAR;
+
+       /* Set the Division Factor to 128 */
+       ADCSRA |= (BV(ADPS0) | BV(ADPS1) | BV(ADPS2));
+}
+
+/** Set the initial reference */
+void adc_set_vref_avcc(void)
+{
+       ADMUX &= ~BV(REFS1);
+       ADMUX |= BV(REFS0);
+}
+
+/** Read the specified AI channel */
+int adc_read_ai_channel(int channel)
+{
+       adc_set_active_ain(channel);
+       timer_udelay(STABILIZING_AI_CHANNEL_TIME);
+       START_CONVERTION;
+
+       while(ADCSRA & BV(ADSC))
+       {
+               /*
+                * Intentionally empty loop.
+                * It waits the convertion to be completed by ADC
+                */
+       }
+
+       ADCSRA |= BV(ADIF);
+
+       uint16_t val;
+       val = ADCL;
+       val |= (uint16_t)ADCH << 8;
+
+       return val;
+}