core/adc/adc.c

   1 /**************************************************************************/
   2 /*!
   3     @file     adc.c
   4     @author   K. Townsend (microBuilder.eu)
   5     @date     22 March 2010
   6     @version  0.10
   7
   8     @section Description
   9
  10     SW-based single-channel A/D conversion.  If you wish to convert
  11     multiple ADC channels simultaneously, this code will need to be
  12     modified to work in BURST mode.
  13
  14     @section Example
  15
  16     @code
  17     #include "core/cpu/cpu.h"
  18     #include "core/adc/adc.h"
  19
  20     void main (void)
  21     {
  22       cpuInit();
  23       adcInit();
  24
  25       uint32_t results = 0;
  26       while(1)
  27       {
  28         // Get A/D conversion results from A/D channel 0
  29         results = adcRead(0);
  30       }
  31     }
  32     @endcode
  33
  34     @section LICENSE
  35
  36     Software License Agreement (BSD License)
  37
  38     Copyright (c) 2010, microBuilder SARL
  39     All rights reserved.
  40
  41     Redistribution and use in source and binary forms, with or without
  42     modification, are permitted provided that the following conditions are met:
  43     1. Redistributions of source code must retain the above copyright
  44     notice, this list of conditions and the following disclaimer.
  45     2. Redistributions in binary form must reproduce the above copyright
  46     notice, this list of conditions and the following disclaimer in the
  47     documentation and/or other materials provided with the distribution.
  48     3. Neither the name of the copyright holders nor the
  49     names of its contributors may be used to endorse or promote products
  50     derived from this software without specific prior written permission.
  51
  52     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  53     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  54     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  55     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  56     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  57     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  58     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  59     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  60     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  61     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  62
  63  */
  64 /**************************************************************************/
  65
  66 #include "adc.h"
  67
  68 static bool _adcInitialised = false;
  69 static uint8_t _adcLastChannel = 0;
  70
  71 /**************************************************************************/
  72 /*!
  73     @brief Returns the conversion results on the specified ADC channel.
  74
  75     This function will manually start an A/D conversion on a single
  76     channel and return the results.
  77
  78     @param[in]  channelNum
  79                 The A/D channel [0..7] that will be used during the A/D
  80                 conversion.  (Note that only A/D channel's 0..3 are
  81                 configured by default in adcInit.)
  82
  83     @return     0 if an overrun error occured, otherwise a 10-bit value
  84                 containing the A/D conversion results.
  85     @warning    Only AD channels 0..3 are configured for A/D in adcInit.
  86                 If you wish to use A/D pins 4..7 they will also need to
  87                 be added to the adcInit function.
  88 */
  89 /**************************************************************************/
  90 uint32_t adcReadSingle (uint8_t channelNum)
  91 {
  92   if (!_adcInitialised) adcInit();
  93
  94   uint32_t regVal, adcData;
  95
  96   /* make sure that channel number is 0..7 */
  97   if ( channelNum >= 8 )
  98   {
  99     // ToDo: Change this to throw an exception back
 100     channelNum = 0;
 101   }
 102
 103   /* Deselect all channels */
 104   ADC_AD0CR &= ~ADC_AD0CR_SEL_MASK;
 105
 106   /* Start converting now on the appropriate channel */
 107   ADC_AD0CR |= ADC_AD0CR_START_STARTNOW | (1 << channelNum);
 108
 109   /* wait until end of A/D convert */
 110   while ( 1 )
 111   {
 112     // Get data register results for the requested channel
 113     switch (channelNum)
 114     {
 115       case 0:
 116         regVal = (*(pREG32(ADC_AD0DR0)));
 117         break;
 118       case 1:
 119         regVal = (*(pREG32(ADC_AD0DR1)));
 120         break;
 121       case 2:
 122         regVal = (*(pREG32(ADC_AD0DR2)));
 123         break;
 124       case 3:
 125         regVal = (*(pREG32(ADC_AD0DR3)));
 126         break;
 127       case 4:
 128         regVal = (*(pREG32(ADC_AD0DR4)));
 129         break;
 130       case 5:
 131         regVal = (*(pREG32(ADC_AD0DR5)));
 132         break;
 133       case 6:
 134         regVal = (*(pREG32(ADC_AD0DR6)));
 135         break;
 136       case 7:
 137         regVal = (*(pREG32(ADC_AD0DR7)));
 138         break;
 139       default:
 140         regVal = (*(pREG32(ADC_AD0DR0)));
 141         break;
 142     }
 143
 144     /* read result of A/D conversion */
 145     if (regVal & ADC_DR_DONE)
 146     {
 147       break;
 148     }
 149   }
 150
 151   /* stop ADC */
 152   ADC_AD0CR &= ~ADC_AD0CR_START_MASK;
 153
 154   /* return 0 if an overrun occurred */
 155   if ( regVal & ADC_DR_OVERRUN )
 156   {
 157     return (0);
 158   }
 159
 160   /* return conversion results */
 161   adcData = (regVal >> 6) & 0x3FF;
 162   return (adcData);
 163 }
 164
 165 /**************************************************************************/
 166 /*!
 167     @brief Returns the conversion results on the specified ADC channel.
 168
 169     This function will manually start an A/D conversion on a single
 170     channel and return the results.  If ADC Averaging is enabled
 171     (via ADC_AVERAGING_ENABLE) the specified number of values will be
 172     samples from the ADC and the average value will be returned.
 173
 174     @param[in]  channelNum
 175                 The A/D channel [0..7] that will be used during the A/D
 176                 conversion.  (Note that only A/D channel's 0..3 are
 177                 configured by default in adcInit.)
 178
 179     @return     0 if an overrun error occured, otherwise a 10-bit value
 180                 containing the A/D conversion results.
 181
 182     @warning    Only AD channels 0..3 are configured for A/D in adcInit.
 183                 If you wish to use A/D pins 4..7 they will also need to
 184                 be added to the adcInit function.
 185 */
 186 /**************************************************************************/
 187 uint32_t adcRead (uint8_t channelNum)
 188 {
 189   if (!_adcInitialised) adcInit();
 190
 191   #if ADC_AVERAGING_ENABLE
 192     uint32_t adcTotal, i;
 193     adcTotal = 0;
 194     for (i=0; i<ADC_AVERAGING_SAMPLES;i++)
 195     {
 196       adcTotal += adcReadSingle(channelNum);
 197     }
 198     return adcTotal/ADC_AVERAGING_SAMPLES;
 199   #else
 200     return adcReadSingle(channelNum);
 201   #endif
 202 }
 203
 204 /**************************************************************************/
 205 /*!
 206     @brief      Initialises the A/D converter and configures channels 0..3
 207                 for 10-bit, SW-controlled A/D conversion.
 208
 209     @return     Nothing
 210 */
 211 /**************************************************************************/
 212 void adcInit (void)
 213 {
 214   /* Disable Power down bit to the ADC block. */
 215   SCB_PDRUNCFG &= ~(SCB_PDRUNCFG_ADC);
 216
 217   /* Enable AHB clock to the ADC. */
 218   SCB_SYSAHBCLKCTRL |= (SCB_SYSAHBCLKCTRL_ADC);
 219
 220   /* Digital pins need to have the 'analog' bit set in addition
 221      to changing their pin function */
 222
 223   /* Set AD0 to analog input */
 224   IOCON_JTAG_TDI_PIO0_11 &= ~(IOCON_JTAG_TDI_PIO0_11_ADMODE_MASK |
 225                               IOCON_JTAG_TDI_PIO0_11_FUNC_MASK |
 226                               IOCON_JTAG_TDI_PIO0_11_MODE_MASK);
 227   IOCON_JTAG_TDI_PIO0_11 |=  (IOCON_JTAG_TDI_PIO0_11_FUNC_AD0 &
 228                               IOCON_JTAG_TDI_PIO0_11_ADMODE_ANALOG);
 229
 230   /* Set AD1 to analog input */
 231   IOCON_JTAG_TMS_PIO1_0 &=  ~(IOCON_JTAG_TMS_PIO1_0_ADMODE_MASK |
 232                               IOCON_JTAG_TMS_PIO1_0_FUNC_MASK |
 233                               IOCON_JTAG_TMS_PIO1_0_MODE_MASK);
 234   IOCON_JTAG_TMS_PIO1_0 |=   (IOCON_JTAG_TMS_PIO1_0_FUNC_AD1 &
 235                               IOCON_JTAG_TMS_PIO1_0_ADMODE_ANALOG);
 236
 237   /* Set AD2 to analog input */
 238   IOCON_JTAG_TDO_PIO1_1 &=  ~(IOCON_JTAG_TDO_PIO1_1_ADMODE_MASK |
 239                               IOCON_JTAG_TDO_PIO1_1_FUNC_MASK |
 240                               IOCON_JTAG_TDO_PIO1_1_MODE_MASK);
 241   IOCON_JTAG_TDO_PIO1_1 |=   (IOCON_JTAG_TDO_PIO1_1_FUNC_AD2 &
 242                               IOCON_JTAG_TDO_PIO1_1_ADMODE_ANALOG);
 243
 244   /* Set AD3 to analog input */
 245   IOCON_JTAG_nTRST_PIO1_2 &= ~(IOCON_JTAG_nTRST_PIO1_2_ADMODE_MASK |
 246                                IOCON_JTAG_nTRST_PIO1_2_FUNC_MASK |
 247                                IOCON_JTAG_nTRST_PIO1_2_MODE_MASK);
 248   IOCON_JTAG_nTRST_PIO1_2 |=  (IOCON_JTAG_nTRST_PIO1_2_FUNC_AD3 &
 249                                IOCON_JTAG_nTRST_PIO1_2_ADMODE_ANALOG);
 250
 251   /* Note that in SW mode only one channel can be selected at a time (AD0 in this case)
 252      To select multiple channels, ADC_AD0CR_BURST_HWSCANMODE must be used */
 253   ADC_AD0CR = (ADC_AD0CR_SEL_AD0 |                     /* SEL=1,select channel 0 on ADC0 */
 254               (((CFG_CPU_CCLK / SCB_SYSAHBCLKDIV) / 1000000 - 1 ) << 8) |   /* CLKDIV = Fpclk / 1000000 - 1 */
 255               ADC_AD0CR_BURST_SWMODE |                 /* BURST = 0, no BURST, software controlled */
 256               ADC_AD0CR_CLKS_10BITS |                  /* CLKS = 0, 11 clocks/10 bits */
 257               ADC_AD0CR_START_NOSTART |                /* START = 0 A/D conversion stops */
 258               ADC_AD0CR_EDGE_RISING);                  /* EDGE = 0 (CAP/MAT signal falling, trigger A/D conversion) */
 259
 260   /* Set initialisation flag */
 261   _adcInitialised = true;
 262
 263   /* Set last channel flag to 0 (initialised above) */
 264   _adcLastChannel = 0;
 265
 266   return;
 267 }