main.cpp

00001 #include "mbed.h"
00002 // Use SPI port to control MAX110/111 Analog to digital converter
00003 // MAX110 is split-supply device, MAX111 single supply.
00004 // Devices require 5v for full performance, may be testable at 3.3v
00005 // 
00006 //
00007 // Conversion is SLOW. 
00008 //
00009 // Data is clocked in on rising edges so SPI 0,0 or SPI 1,1. 
00010 
00011 Serial pc(USBTX, USBRX); // tx, rx
00012 
00013 SPI spi(p5, p6, p7); // mosi, miso, sclk
00014 DigitalOut max_cs(p22);
00015 DigitalIn  max_busy(p23);
00016 
00017 //module libmax110
00018 //
00019 //const
00020 #define      max_12bit 0x9200
00021 #define      max_13bit 0x8600
00022 #define      max_14bit 0x8c00
00023 #define      max_div4  0x0100
00024 #define      max_div2  0x0080
00025 #define      max_chan1 0x0000
00026 #define      max_chan2 0x0010
00027 #define      max_full  0x000c
00028 //#define      max_gain  0b0000000000001000
00029 #define      max_ofs   0x0004
00030 //
00031 //   procedure max_init(dim mode as word, dim byref port as //byte, dim cs,bf as byte)
00032 //
00033 //   mode must be one of max_12bit, max_13bit, max_14bit
00034 //   mode may be modified by "or-ing" with max_div2 or max_div4 to set clock divider
00035 //   mode may be modified by "or-ing" with max_chan1 or //max_chan2 to set input channel
00036 //   mode may be modified by "or-ing" with a calibration type //max_full,max_ofs
00037 //
00038 //   port is the port the busy and cs pins are connected to (doesn't have to be PORTC)
00039 //   cs is the bit number for the chip select pin
00040 //   bf is the bit number for the busy flag pin
00041 //
00042 //   function max_read(dim byref data as integer) as boolean
00043 //
00044 // notes returns true if a value was read, immediately restarts converter
00045 // otherwise returns false
00046 //
00047 // result is integer, valid results are from -16384 through 16383.
00048 // values beyond this are overrange
00049 //
00050 //
00051 // MAX110/111 Control register bits
00052 // 15         !NOOP   Set to 1 for action, 0 for pass-through
00053 // 14         NU, set to 0
00054 // 13         NU, set to 0
00055 //                             CONV 4,3,2,1
00056 // 12         CONV4                 1 0 0 1  20ms
00057 // 11         CONV3                 0 0 1 1  40ms
00058 // 10         CONV2                 0 1 1 0  160ms
00059 //  9         CONV1                 0 0 0 0  200ms SPECIAL
00060 //                    SPECIAL = NO INTERNAL GAIN CALIBRATION, FIX IN SOFTWARE
00061 //  8         DV4           1=DIVIDE XCLK BY 4
00062 //  7         DV2           1=DIVIDE XCLK BY 2
00063 //
00064 //  6         NU, set to 0
00065 //  5         NU, set to 0
00066 
00067 //  4         CHS               0:CHANNEL 1   1:CHANNEL2
00068 //
00069 //                                    CAL NUL FUNCTION
00070 //                                     1   1   INTERNAL ZERO (PERFORM FIRST)
00071 //  3         GAIN CAL                 1   0   INTERNAL GAIN (NEXT)
00072 //  2         OFFSET NUL               0   1   INPUT NUL (LAST)
00073 //                                     0   0   NORMAL CONVERT
00074 //  1         PDX POWER DOWN OSC
00075 //  0         PD POWER DOWN ADC
00076 //
00077 //
00078 unsigned int max_mode; 
00079 //
00080 void max_setup(unsigned int mmode)
00081 {
00082   max_mode=mmode;
00083   max_cs=0;
00084       spi.write(0);
00085       spi.write(0);
00086   max_cs=1;
00087   // not sure why the above step helps but it seems to improve restarts after random
00088   // reset
00089   max_cs=0;
00090       spi.write((max_mode & 0xff00) >> 8);
00091       spi.write(max_mode & 0xff);
00092   max_cs=1;
00093 }
00094 
00095 
00096 int max_read(int *data)
00097 {
00098   if (max_busy)
00099   {
00100     if (max_mode & 0x0c)
00101     {
00102       max_mode = max_mode - 0x04;
00103       
00104       max_cs=0;
00105       spi.write((max_mode & 0xff00) >> 8);
00106       spi.write(max_mode & 0xff);
00107       max_cs=1;
00108       wait(0.1);
00109       return(false);
00110     }
00111     else
00112     {
00113       short t;
00114       max_cs=0;
00115       t    =spi.write((max_mode & 0xff00) >> 8);
00116       t    =spi.write(max_mode & 0xff) | (t<<8);
00117       *data= (int) t;
00118       max_cs=1;
00119       return(true);
00120     }
00121   }
00122   else
00123   {
00124     return(false);
00125   }
00126 }
00127 
00128 
00129 int main() {
00130     spi.format(8,0);
00131     spi.frequency(100000);
00132     max_cs=1;
00133 //    pc.printf("Start converter\r\n");
00134     max_setup(max_14bit | max_full);
00135     while(1) {
00136       int val;
00137       val=0;
00138       if (max_read(&val))
00139       {
00140         pc.printf("Readout: %d \r\n",val);
00141 // optional: force a recalibrate
00142 //       max_setup(max_14bit | max_full);
00143       }
00144     }
00145 }