jens
a22ffe8384
git-svn-id: http://moon:8086/svn/projects/HendiControl@29 fda53097-d464-4ada-af97-ba876c37ca34
90 lines
1.3 KiB
Python
90 lines
1.3 KiB
Python
#!/usr/bin/python
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import spidev
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import time
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import os
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# Open SPI bus
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spi = spidev.SpiDev()
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spi.open(0,0)
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spi.max_speed_hz=100000
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spi.mode = 0b01
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def read_reg(addr):
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reg = spi.xfer([addr, 0xFF]);
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return reg[1]
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def write_reg(addr, data):
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spi.xfer([addr+0x80, data]);
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def read_digits():
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msb = read_reg(0x01)
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lsb = read_reg(0x02)
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digits = float(256*msb + lsb)/2
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return digits
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def calc_R(Rref, digits):
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k = digits / 8192 / 4
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R = k*Rref
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return R
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def vanDusenLut (R0, Tmin, Tmax, dT):
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a = +3.90830e-03;
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b = -5.77500e-07;
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c = -4.18301e-12;
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Rv = []
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Tv = []
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T = Tmin
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while T <= Tmax:
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R = R0*(1 + a*T + b*T**2)
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if T < 0.0:
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R += R0*c*(T - 100)*T**3;
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Rv.append(R)
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Tv.append(T)
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T += dT
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return Rv, Tv
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def vanDusen_temp(Rmeas):
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RLut, TLut = vanDusenLut(100, -150, +500, 1.0)
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# Find candidate
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i = 0
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for R in RLut:
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if R > Rmeas:
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break
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i += 1
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# Linear interpolation
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R0 = RLut[i-1]
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R1 = RLut[i]
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T0 = TLut[i-1]
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T1 = TLut[i]
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dR = R1 - R0
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dT = T1 - T0
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k = (Rmeas-R0)/dR
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T = T0 + dT*k
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return T
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# Main
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write_reg(0x00, 0xA3)
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digits = read_digits()
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R = calc_R(430, digits)
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T = vanDusen_temp(R)
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print("R={:.3f} Ohm, T={:.2f} degC".format(R, T))
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for i in range (0, 8):
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print("Reg[0x{}]: 0x{:02X}".format(i, read_reg(i)))
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print("End of program")
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