nes-proj/cpu/mc1322x/lib/adc.c

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2011-03-11 21:20:41 +00:00
/*
* Copyright (c) 2010, Mariano Alvira <mar@devl.org> and other contributors
* to the MC1322x project (http://mc1322x.devl.org)
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS 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 THE INSTITUTE OR 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.
*
* This file is part of libmc1322x: see http://mc1322x.devl.org
* for details.
*
*
*/
#include <stdint.h>
#include "crm.h"
#include "adc.h"
#include "gpio-util.h"
//#define ADC_CHANS_ENABLED 0x3F // channels 0-5 enabled
//#define ADC_CHANS_ENABLED 0x7E // channels 1-6 enabled
//#define ADC_CHANS_ENABLED (1 << 6) // only channel 6 enabled
#define ADC_CHANS_ENABLED 0x1FF // all channels, including battery reference voltage
//#define ADC_PRESCALE_VALUE 24 // divide by 24 for 1MHz.
#define ADC_SAMPLE_FREQ 400 // Hz (minimum of ~366.21 Hz)
#define ADC_PRESCALE_VALUE (REF_OSC / ADC_SAMPLE_FREQ)
#define ADC_USE_TIMER 0
#define ADC_USE_INTERRUPTS 0 // incomplete support
uint16_t adc_reading[NUM_ADC_CHAN];
void ADC_flush(void) {
while(ADC->FIFO_STATUSbits.EMPTY == 0) ADC->FIFO_READ;
}
uint16_t ADC_READ(void) {
while(ADC->FIFO_STATUSbits.EMPTY); // loop while empty
return ADC->FIFO_READ; // upper 4 bits are channel number
}
void adc_service(void) {
uint16_t value;
uint8_t channel;
while (ADC->FIFO_STATUSbits.EMPTY == 0) {
value = ADC->FIFO_READ;
channel = value >> 12;
if (channel < NUM_ADC_CHAN) adc_reading[channel] = value & 0xFFF;
}
}
void adc_init(void) {
uint8_t n;
ADC->CLOCK_DIVIDER = 80; // 300 KHz
ADC->PRESCALE = ADC_PRESCALE_VALUE - 1; // divide by 24 for 1MHz.
ADC->CONTROL = 1;
// The ON-TIME must always be 10µs or greater - typical On-Time value = 0x000A (10dec)
ADC->ON_TIME = 10;
/*
NOTE
The ADC analog block requires 6 ADC_Clocks per conversion, and the
ADC_Clock must 300kHz or less. With 6 clocks/conversion and a 33.33µs
clock period:
* The ADC convert time must always be 20µs or greater
* If the ADC_Clock is a frequency lower than 300kHz, the convert time
must always be 6 ADC_Clock periods or greater
* For override mode, extend convert time to 40µs minimum or greater
For the convert time:
* This delay is a function of the Prescale Clock (typically 1 MHz)
* The register must be initialized for proper operation
* For a 20µs convert time with 1MHz, value = 0x0014 (20dec)
* If convert time is insufficient, inaccurate sample data will result
*/
ADC->CONVERT_TIME = 1000000 / (115200 / 8) - 1;
ADC->MODE = 0; // Automatic
#if ADC_USE_INTERRUPTS
ADC->FIFO_CONTROL = 7;
#else
ADC->FIFO_CONTROL = 0;
#endif
#if ADC_USE_TIMER
ADC->SR_1_HIGH = 0x0000;
ADC->SR_1_LOW = (REF_OSC / ADC_PRESCALE_VALUE) / (115200 / 8) + 1;
#endif
ADC->SEQ_1 = 0
#if ADC_USE_TIMER
| (1 << 15) // sequence based on Timer 1.
#else
| (0 << 15) // sequence based on convert time.
#endif
| ADC_CHANS_ENABLED;
ADC->CONTROL = 0xF001
//#if ADC_USE_TIMER
| (1 << 1) // Timer 1 enable
//#endif
;
ADC->OVERRIDE = (1 << 8);
for (n=0; n<=8; n++) {
if ((ADC_CHANS_ENABLED >> n) & 1) {
gpio_select_function(30 + n, 1); // Function 1 = ADC
gpio_set_pad_dir(30 + n, PAD_DIR_INPUT);
}
}
}