text: /****************************************************************************
   *
   *   Copyright (c) 2012 PX4 Development Team. 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 PX4 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 COPYRIGHT HOLDERS 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
   * COPYRIGHT OWNER 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.
   *
   ****************************************************************************/
  
  /**
   * @file adc.c
   *
   * Simple ADC support for PX4IO on STM32.
   */
  #include <px4_platform_common/px4_config.h>
  #include <stdint.h>
  
  #include <nuttx/arch.h>
  #include <arch/stm32/chip.h>
  #include <stm32.h>
  
  #include <drivers/drv_hrt.h>
  #include <perf/perf_counter.h>
  
  #define DEBUG
  #include "px4io.h"
  
  /*
   * Register accessors.
   * For now, no reason not to just use ADC1.
   */
  #define REG(_reg)	(*(volatile uint32_t *)(STM32_ADC1_BASE + _reg))
  
  #define rSR		REG(STM32_ADC_SR_OFFSET)
  #define rCR1		REG(STM32_ADC_CR1_OFFSET)
  #define rCR2		REG(STM32_ADC_CR2_OFFSET)
  #define rSMPR1		REG(STM32_ADC_SMPR1_OFFSET)
  #define rSMPR2		REG(STM32_ADC_SMPR2_OFFSET)
  #define rJOFR1		REG(STM32_ADC_JOFR1_OFFSET)
  #define rJOFR2		REG(STM32_ADC_JOFR2_OFFSET)
  #define rJOFR3		REG(STM32_ADC_JOFR3_OFFSET)
  #define rJOFR4		REG(STM32_ADC_JOFR4_OFFSET)
  #define rHTR		REG(STM32_ADC_HTR_OFFSET)
  #define rLTR		REG(STM32_ADC_LTR_OFFSET)
  #define rSQR1		REG(STM32_ADC_SQR1_OFFSET)
  #define rSQR2		REG(STM32_ADC_SQR2_OFFSET)
  #define rSQR3		REG(STM32_ADC_SQR3_OFFSET)
  #define rJSQR		REG(STM32_ADC_JSQR_OFFSET)
  #define rJDR1		REG(STM32_ADC_JDR1_OFFSET)
  #define rJDR2		REG(STM32_ADC_JDR2_OFFSET)
  #define rJDR3		REG(STM32_ADC_JDR3_OFFSET)
  #define rJDR4		REG(STM32_ADC_JDR4_OFFSET)
  #define rDR		REG(STM32_ADC_DR_OFFSET)
  
  perf_counter_t		adc_perf;
  
  int
  adc_init(void)
  {
  	adc_perf = perf_alloc(PC_ELAPSED, "adc");
  
  	/* put the ADC into power-down mode */
  	rCR2 &= ~ADC_CR2_ADON;
  	up_udelay(10);
  
  	/* bring the ADC out of power-down mode */
  	rCR2 |= ADC_CR2_ADON;
  	up_udelay(10);
  
  	/* do calibration if supported */
  #ifdef ADC_CR2_CAL
  	rCR2 |= ADC_CR2_RSTCAL;
  	up_udelay(1);
  
  	if (rCR2 & ADC_CR2_RSTCAL) {
  		return -1;
  	}
  
  	rCR2 |= ADC_CR2_CAL;
  	up_udelay(100);
  
  	if (rCR2 & ADC_CR2_CAL) {
  		return -1;
  	}
  
  #endif
  
  	/*
  	 * Configure sampling time.
  	 *
  	 * For electrical protection reasons, we want to be able to have
  	 * 10K in series with ADC inputs that leave the board. At 12MHz this
  	 * means we need 28.5 cycles of sampling time (per table 43 in the
  	 * datasheet).
  	 */
  	rSMPR1 = 0b00000000011011011011011011011011;
  	rSMPR2 = 0b00011011011011011011011011011011;
  
  	rCR2 |=	ADC_CR2_TSVREFE;		/* enable the temperature sensor / Vrefint channel */
  
  	/* configure for a single-channel sequence */
  	rSQR1 = 0;
  	rSQR2 = 0;
  	rSQR3 = 0;	/* will be updated with the channel at conversion time */
  
  	return 0;
  }
  
  /*
    return one measurement, or 0xffff on error
   */
  uint16_t
  adc_measure(unsigned channel)
  {
  
  	perf_begin(adc_perf);
  
  	/* clear any previous EOC */
  	rSR = 0;
  	(void)rDR;
  
  	/* run a single conversion right now - should take about 60 cycles (a few microseconds) max */
  	rSQR3 = channel;
  	rCR2 |= ADC_CR2_ADON;
  
  	/* wait for the conversion to complete */
  	hrt_abstime now = hrt_absolute_time();
  
  	while (!(rSR & ADC_SR_EOC)) {
  
  		/* never spin forever - this will give a bogus result though */
  		if (hrt_elapsed_time(&now) > 100) {
  			perf_end(adc_perf);
  			return 0xffff;
  		}
  	}
  
  	/* read the result and clear EOC */
  	uint16_t result = rDR;
  	rSR = 0;
  
  	perf_end(adc_perf);
  	return result;
  }
  