'{$STAMP BS2SX}
''
'' Programmer:     Craig Stuart Sapp <craig@ccrma.stanford.edu>
'' Programmer:     Florian Vogt <fvogt@ccrma.stanford.edu>
'' Creation Date:  Sat 10-23-1999
'' Last Modified:  Sat 10-23-1999
'' Filename:       max1270.bsx
'' Syntax:         Basic Stamp IIsx
''
'' Description:    This program reads in samples from the
''                 Maxim 1270 (a 12-bit, 8 channels A/D chip).
''                 The sampled value is then printed on the computer screen.
''

clockpin    con     7    ' synchronous clock pin to control MAXIM 1270 chip
inputpin    con     8    ' for reading data from MAXIM 1270 chip
outputpin   con     9    ' for sending the controlbyte to the MAX1270 chip
sleeptime   con   250    ' time in milliseconds to wait between samples
msb         con     1    ' mode for shiftout functions: msb
behindclock con     2    ' mode for shiftin: msb post clock

' the MAX1270 control byte below is composed of several fields
'  listed here from MSB to LSB bits:
'  bit7:     defines the beginning of the control byte
'  bits4-6:  selects the A/D channel (0-7).
'  bit3:     choose the A/D voltage range, 0=5v, 1=10v
'  bit2:     choose polar/bipolar range, 0=positive, 1=positive/negative
'  bit0:     choose clock mode: 0=internal, 1=external
'  bits0-1:  10=standby, 11=power-down (clock mode unaffected)
'
' the control byte 1,000,00,01 means: channel 0, 0 to +5v, external clock:
controlbyte    con   %10000001


' Variables:

bytea    var     byte         ' for holding first 8 MSBs of 12-bit sample
byteb    var     byte         ' for holding 4 LSBs of 12-bit sample


' According to BASIC Stamp Programming Manual v1.9, page 208:
' "Unused pins that are not connected to circuitry should be set to output" 
' to minimize power consumption, which is done here:
DIRS = %1111111101111111
' Don't set pins connected to input circuitry to be output, or you can
' damage the Basic Stamp.


' Commands used below:
'
' SHIFTOUT     outputpin, clockpin, mode, [data \ bits]
'   outputpin = pin to send synchronous data on
'   clockpin  = pin to send synchronous clock signal
'   mode      = 0=LSB, 1=MSB
'   data      = data to send
'   bits      = number of bits in data field to send (default = 8);
'
' SHIFTIN     inputpin, clockpin, mode, [variable \ bits]
'   inputin   = pin to receive synchronous data on
'   clockpin  = pin to send synchronous clock signal
'   mode      = 0=LSB, 1=MSB
'   variable  = location to store the bits
'   bits      = number of bits to input (default = 8);
'

top:

   ' first tell the MAX1270 that you want a sample from channel 0
   shiftout    outputpin, clockpin, msb, [controlbyte \ 8]

   ' wait 4 clock cycles until the sample is ready to be returned
   shiftout    outputpin, clockpin, msb, [0 \ 4]

   ' read in the returned sample from the MAX1270 chip
   shiftin     inputpin, clockpin, behindclock, [bytea \ 8]

   ' finish reading in the data (12-bit sample)
   shiftin     inputpin, clockpin, behindclock, [byteb \ 4]

   debug dec ? bytea
   debug dec ? byteb
   debug cr

   ' now wait a while before taking another sample
   pause       sleeptime

goto top: