;pro fit_offset

;restore, 'offset_data.sav'
; loads val, which is [frame, col, row] with 
; frame = 0-4, row and col are both 0 - 31
; Stored data are the digitized Vout.

; Convert val to Voltage
range = 10.d
nsteps = 4095.d
res = range / nsteps



;volts = pixeldc * res
volts = 3.* (pixeldc / ( 2.0^12.))

; volts[0, *, *] is Vout with Vin set to 0 V
; volts[1, *, *] is Vout with Vin set to 2 V
; volts[2, *, *] is Preamp Output Volt (should be uniform and ~ 0.1 V)
; volts[3, *, *] is leakage (should be uniform and ~ 1.6 V)
; volts[4, *, *] is DC level at shaper (?)

; First thing is to generate a Vout -> Vin
; map, assuming linearity:
; Vin = m * Vout + offset
; 2 = m[*, *] * (volts[1, *, *] - volts[0, *, *])
; m[*, *] = 2 / (volts[1, *, *] - volts[0, *, *])
; offset = - m[*, *] * volts[0, *, *]

slope = 2.d / (reform(volts[1, *, *]) - reform(volts[0, *, *]))
offset = -slope * reform(volts[0, *, *])

for i = 2, 4 do volts[i, *, *] = volts[i, *, *] * slope + offset

zerolevel = reform(volts[0, *, *])
raillevel = reform(volts[1, *, *])
preAmp = reform(volts[2, *, *])
leakage = reform(volts[3, *, *])
dclevel = reform(volts[4, *, *])

end