# GPIB interface for printer port wrapper

require "prnprtLX"
#require "prnprt95"

class Gpib

# cable connections
# D-sub 25pin to amphenol 24pin
# No.	printer		i/o	GPIB	No.	+/-
#  1	/STROBE		O	-DAV	6	-
#  2	DATA0		IO	DIO1	1	+
#  3	DATA1		IO	DIO2	2	+
#  4	DATA2		IO	DIO3	3	+
#  5	DATA3		IO	DIO4	4	+
#  6	DATA4		IO	DIO5	13	+
#  7	DATA5		IO	DIO6	14	+
#  8	DATA6		IO	DIO7	15	+
#  9	DATA7		IO	EOI	5	+
# 10	/ACK		I	SRQ	10	+
# 11	BUSY		I	NRFD	7	-
# 12	PE		I	NDAC	8	+
# 13	SLCT		I	DAV	6	+
# 14	/AUTOFXINIT	O	ATN	11	-
# 15	/ERROR		I			?
# 16	/INIT		O	-NRFD	7	+
# 17	/SLCTIN		O	-NDAC	8	-
# 18-25	GND		-	GND	18-24
#	NC			IFC	9
#	GND			REN	17
#	NC			DIO8	16
#				shield	12
# for DAV, NDAC, and NRFD, connect as follows
#	I ---C---signal
#	O ---B
#	GND--E
#		C,B,E are pins of NPN type transistor (for example C945)

class Error < StandardError
end

def initialize
	@dev,@pad,@sad,@tmo = -1,-1,-1,-1
	@p=PrnPort::new
	set
end

attr_accessor :pad
attr_accessor :sad
attr_accessor :tmo

#commands
GTL=0x01; SDC=0x04; PPC=0x05; GET=0x08; TCT=0x09
LLO=0x11; DCL=0x14; PPU=0x15; SPE=0x18; SPD=0x19
MLA=0x20; UNL=0x3f
MTA=0x40; UNT=0x5f

#Timeout values and meanings
TNONE   = 0   # Infinite timeout (disabled)
T10us   = 1; T30us   = 2; T100us  = 3; T300us  = 4   # 10-300 us (ideal)
T1ms    = 5; T3ms    = 6; T10ms   = 7; T30ms   = 8   # 1-30 ms (ideal)
T100ms  = 9; T300ms  =10; T1s     =11; T3s     =12   # 0.1-3 s (ideal)
T10s    =13; T30s    =14; T100s   =15; T300s   =16   # 10-300 s (ideal)
T1000s  =17   # 1000 s (ideal)

def set()
	dav(0); atn(0); nrfd(0); ndac(0); write_data(0)
end

# in
def srq(n=nil)
	@p.status()
	(@p.ack-1).abs
end
# out
def atn(n=nil)
	@p.autofxinit=n
	@p.command()
end

# in/out
def dav(n=nil)
	if n!=nil
		@p.strobe=(n-1).abs
		@p.command()
	else
		@p.status()
		(@p.slct-1).abs
	end
end
def nrfd(n=nil)
	if n!=nil
		@p.init=n
		@p.command()
	else
		@p.status()
		@p.busy
	end
end
def ndac(n=nil)
	if n!=nil
		@p.slctin=(n-1).abs
		@p.command()
	else
		@p.status()
		(@p.pe-1).abs
	end
end


# data
def write_data(d)
	@p.write(d^0xff)
end
def read_data()
	@p.read()^0xff
end

# handshake
def talk(d)
	dav(0)
	if nrfd()==0 and ndac()==0
		print "error\n"
	else
		write_data(d)
		until nrfd()==0 do end
		dav(1)
		until ndac()==0 do end
		dav(0)
	end
end
def listen()
	nrfd(1)
	ndac(1)
	nrfd(0)
	until dav()==1 do end
	nrfd(1)
	r=read_data()
	ndac(0)
	until dav()==0 do end
	ndac(1)
#	nrfd(0)
	return r
end

def command(a)
	atn(1)
	for d in a do talk(d) end
	atn(0)
end

# initialize
def interfaceClear()
end
def deviceClear()
	command([DCL])
end
def selectedDeviceClear(adrs=@pad)
	command([UNL,MLA+adrs,SDC])
end

# remote/local
def remoteEnable()
end
def goToLocal(adrs=@pad)
	command([UNL,MLA+adrs,GTL])
end
def localLockOut(adrs=@pad)
	command([LLO])
end

# trigger
def groupExecuteTrigger(adrs=@pad)
	command([UNL,MLA+adrs,GET])
end

# serial pole

# paralel pole

# functions
def open(bd=0,pad=@pad,sad=@sad,tmo=@tmo,eot=1,eos=0)
	@pad,@sad,@tmo=pad,sad,tmo
end
def write(data)
	set()
	command([UNL,MLA+@pad])
	a=data.unpack("C*")
	a.push(a.pop|0x80)
	for d in a do talk(d) end
	set()
end
def read(n=1024)
	set()
	@p.read()
	command([UNL,MTA+@pad])
	a=[]
	for i in 0...n
		a.push(listen())
		break if a.last&0x80!=0
	end
	a.push(a.pop&0x7f)
	set()
	return a.pack("C*")
end
def rsp()
	set()
	command([SPE,MTA+@pad])
	r=listen()
	command([SPD])
	return
end
def ibclr()
	interfaceClear()
end
end #class