'{$STAMP BS2SX}
''
'' Programmer:     Craig Stuart Sapp <craig@ccrma.stanford.edu>
'' Creation Date:  Mon Oct 16 15:52:44 PDT 2000
'' Last Modified:  Mon Oct 16 16:13:52 PDT 2000
'' Filename:       midi8.bsx
'' Based On:       midi1270.bsx, max1270.bsx, cout.bsx
'' Syntax:         Basic Stamp IIsx
''
'' Description:    This program is a variation on midi1270. Data from all
''   8 channels of the Maxim 1270 are sampled and sent via MIDI using the
''   command 0xA0. The first parameter MIDI byte specifies the channel number
''   (0-7) and the second parameter byte gives the sampled data variable.
''

sleeptime    con   10     ' time in milliseconds to wait between sensor samples

' Data Variables:
channel  var     byte     ' for holding first MIDI parameter byte (sensor chan.)
bytea    var     byte     ' for holding first 7 MSBs of 12-bit sample
byteb    var     byte     ' for holding 5 LSBs of 12-bit sample (ignored)

' MIDI output variables
midicommand  con   $A0    ' use MIDI aftertouch command to send sensor data
midioutpin   con     7    ' output pin on which to send MIDI data
midirate     con    60    ' baude mode for serout: (2500000/31250)-20 msec
                          ' note that this value should be 12 for BS2.
                          ' Serial rate for MIDI is 31,250 data bits/sec.
outpause     con     0    ' pause time in units of 0.4 millisec between bytes.
                          ' On the BS2, units are 1.0 millisec.  A value of
			  ' zero means do not pause between successive MIDI
                          ' bytes when sending arrays of MIDI data.

' Maxim 1270 chip variables
clockpin     con    11    ' synchronous clock pin to control MAXIM 1270 chip
cspin        con    10    ' chip select pin for MAXIM 1270 (only needed if more
                          ' than one chip)
outputpin    con     9    ' for sending the controlbyte to the MAX1270 chip
inputpin     con     8    ' for reading data from MAXIM 1270 chip
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:
basiccontrol  con   %10000001 
controlbyte   var   byte         ' variable for adding channel to basiccontrol


' 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:

   for channel = 0 to 7
      gosub ReadSensorData      ' take a sensor reading on specified channel
      gosub SendSensorData      ' send reading out via MIDI
   next

   ' wait a while before taking another sample
   pause       sleeptime

goto top



''''''''''''''''''''''''''''''
''
'' ReadSensorData -- sends a command to the A/D converter chip
''     requesting data.  Then reads the returning data and stores
''     the 7 most significant bits in bytea variable and the 5 
''     least significant bits in the byteb variable.
''

ReadSensorData:
   ' create the control byte with the specified channel to sample
   controlbyte = basiccontrol ^ (channel << 4)

   ' clear the storage bytes for sensor data
   bytea = 0
   byteb = 0

   ' first tell the MAX1270 that you want a sample 
   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 \ 7]

   ' finish reading in the data (12-bit sample)
   shiftin     inputpin, clockpin, behindclock, [byteb \ 5]

'  debug dec ? bytea
'  debug dec ? byteb
'  debug cr

return



''''''''''''''''''''''''''''''
''
'' SendSensorData -- send sensor data via a MIDI command through 
''     a TTL (5 volt) serial line at 31.25 kBit speed.  
''

SendSensorData:
   serout midioutpin, midirate, outpause, [midicommand, channel, bytea]

return