# GP-IB library wrapper for National Instruments gpib-32.dll
# written in 2003
# bug fix at 2010.8.15

require "Win32API"

class Gpib

  class Error < StandardError
  end

  def initialize
    @dev,@pad,@sad,@tmo = -1,-1,-1,-1
    @pad0,@sad0,@tmo0 = @pad,@sad,@tmo	#previous setting
  end

attr_accessor :pad
attr_accessor :sad
attr_accessor :tmo

  def open(bd=0,pad=@pad,sad=@sad,tmo=@tmo,eot=1,eos=0)
    @dev = ibdev(bd,pad,sad,tmo,eot,eos)
    @pad,@sad,@tmo=pad,sad,tmo
    @pad0,@sad0,@tmo0=pad,sad,tmo
    raise Gpib::Error, err_str(thrediberr) if @dev < 0
    @dev
  end

  def write(str)
    setpara
    stat,cnt = ibwrt(str)
    raise Gpib::Error, err_str(stat) if (stat & Stat.assoc("ERR")[1]) > 0
    cnt
  end

  def wait_rqs
    setpara
    mask=(Stat.assoc("TIMO")[1] | Stat.assoc("RQS")[1])
    stat=ibwait(mask)
    raise Gpib::Error, err_str(stat) if (stat & Stat.assoc("ERR")[1]) > 0
  end

  def read(cnt=1024)
    setpara
    buf = ""
    loop do
      stat,b = ibrd(cnt)
      raise Gpib::Error, err_str(stat) if (stat & Stat.assoc("ERR")[1]) > 0
      buf << b
      break if (stat & Stat.assoc("END")[1]) > 0
    end
    return buf
  end

  def rsp
    setpara
    stat, rspr = ibrsp
    raise Gpib::Error, err_str(stat) if (stat & Stat.assoc("ERR")[1]) > 0
    return rspr
  end

  def setpara
    ibpad(@pad) unless @pad==@pad0
    ibsad(@sad) unless @sad==@sad0
    ibtmo(@tmo) unless @tmo==@tmo0
    @pad0,@sad0,@tmo0=@pad,@sad,@tmo
  end
#
#
#constants
#Timeout values and meanings
TNONE   = 0   # Infinite timeout (disabled)
T10us   = 1   # Timeout of 10 us (ideal)
T30us   = 2   # Timeout of 30 us (ideal)
T100us  = 3   # Timeout of 100 us (ideal)
T300us  = 4   # Timeout of 300 us (ideal)
T1ms    = 5   # Timeout of 1 ms (ideal)
T3ms    = 6   # Timeout of 3 ms (ideal)
T10ms   = 7   # Timeout of 10 ms (ideal)
T30ms   = 8   # Timeout of 30 ms (ideal)
T100ms  = 9   # Timeout of 100 ms (ideal)
T300ms  =10   # Timeout of 300 ms (ideal)
T1s     =11   # Timeout of 1 s (ideal)
T3s     =12   # Timeout of 3 s (ideal)
T10s    =13   # Timeout of 10 s (ideal)
T30s    =14   # Timeout of 30 s (ideal)
T100s   =15   # Timeout of 100 s (ideal)
T300s   =16   # Timeout of 300 s (ideal)
T1000s  =17   # Timeout of 1000 s (ideal)

# GPIB status bit vector :
#       global variable ibsta and wait mask
Stat=[
["ERR",1<<15],  # Error detected
["TIMO",1<<14], # Timeout
["END",1<<13],  # EOI or EOS detected
["SRQI",1<<12], # SRQ detected by CIC
["RQS",1<<11],  # Device needs service
["SPOLL",1<<10],
["EVENT",1<<9],
["CMPL",1<<8],  # I/O completed
["LOK",1<<7],   # Local lockout state
["REM",1<<6],   # Remote state
["CIC",1<<5],   # Controller-in-Charge
["ATN",1<<4],   # Attention asserted
["TACS",1<<3],  # Talker active
["LACS",1<<2],  # Listener active
["DTAS",1<<1],  # Device trigger state
["DCAS",1<<0],  # Device clear state
]

# Win32API
Ibdev=Win32API.new("gpib-32","ibdev",["L","L","L","L","L","L"],"L")
Ibfind=Win32API.new("gpib-32","ibfind",["P"],"L")
Ibwait=Win32API.new("gpib-32","ibwait",["L","L"],"L")
Ibwrt=Win32API.new("gpib-32","ibwrt",["L","P","L"],"L")
Ibrd=Win32API.new("gpib-32","ibrd",["L","P","L"],"L")
Thredibcntl=Win32API.new("gpib-32","ThreadIbcntl",[],"L")
Thrediberr=Win32API.new("gpib-32","ThreadIberr",[],"L")
Ibrsp=Win32API.new("gpib-32","ibrsp",["L","P"],"L")
Ibclr=Win32API.new("gpib-32","ibclr",["L"],"L")
Ibpad=Win32API.new("gpib-32","ibpad",["L","L"],"L")
Ibsad=Win32API.new("gpib-32","ibsad",["L","L"],"L")
Ibtmo=Win32API.new("gpib-32","ibtmo",["L","L"],"L")

  def err_str(stat)
    r = []
    for i in 0..15
      r << Stat[i][0] if (stat & Stat[i][1])!=0
    end
    "<" + r.join(",") + ">"
  end

# basic commands
  def ibdev(bd=0,pad=0,sad=0,tmo=T1s,eot=1,eos=0)
    ud = Ibdev.call(bd,pad,sad,tmo,eot,eos)
  end
  def ibfind(name = "dev1")
    @dev = Ibfind.call(name)
  end
  def ibwait(mask)
    Ibwait.call(@dev,mask)
  end
  def ibwrt(str)
    stat = Ibwrt.call(@dev,str,str.size)
    cnt = thredibcntl
    [stat,cnt]
  end
  def ibrd(size = 1024)
    buf = "\000" * size
    stat = Ibrd.call(@dev,buf,size)
    cnt = thredibcntl
    [stat,buf[0,cnt]]
  end
  def thredibcntl
    Thredibcntl.call
  end
  def thrediberr
    Thrediberr.call
  end
  def ibrsp
    rsp = "\0"
    stat = Ibrsp.call(@dev,rsp)
    [stat, rsp.unpack("c")[0]]
  end
  def ibclr
    Ibclr.call(@dev)
  end
  def ibpad(pad)
    Ibpad.call(@dev,pad)
  end
  def ibsad(sad)
    Ibsad.call(@dev,sad)
  end
  def ibtmo(tmo)
    Ibtmo.call(@dev,tmo)
  end

end