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suservo: use addition for offset

This commit is contained in:
Robert Jördens 2018-05-13 11:16:31 +00:00
parent 27f975e7bb
commit d71e4e60a9
2 changed files with 6 additions and 6 deletions
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10
artiq/gateware/suservo/iir.py
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@ -61,7 +61,7 @@ class DSP(Module):
If(self.offset_load,
d.eq(self.offset)
),
ad.eq(d - a),
ad.eq(d + a),
b.eq(self.coeff),
m.eq(ad*b),
p.eq(p + m),
@ -184,7 +184,7 @@ class IIR(Module):
X0 = ADC * 2^(25 - 1 - 16)
X1 = X0 delayed by one cycle
A0 = 2^11
A0*Y0 = A1*Y1 - B0*(X0 - OFFSET) - B1*(X1 - OFFSET)
A0*Y0 = A1*Y1 + B0*(X0 + OFFSET) + B1*(X1 + OFFSET)
Y1 = Y0 delayed by one cycle
ASF = Y0 / 2^(25 - 14 - 1)
@ -196,7 +196,7 @@ class IIR(Module):
B0 --/- A0: 2^11
18 | |
ADC -/-[<<]-/-(-)-/---(x)-(+)-/-[>>]-/-[_/^]-/---[>>]-/- ASF
ADC -/-[<<]-/-(+)-/---(x)-(+)-/-[>>]-/-[_/^]-/---[>>]-/- ASF
16 8 24 | 25 | | 48 11 37 25 | 10 15
OFFSET --/- [z^-1] ^ [z^-1]
24 | | |
@ -632,8 +632,8 @@ class IIR(Module):
logger.debug("state y1[%d,%d]=%#x x0[%d]=%#x x1[%d]=%#x",
i, j, y1, k_j, x0, k_j, x1)
p = (0*(1 << w.shift - 1) + a1*(0 - y1) +
b0*(offset - x0) + b1*(offset - x1))
p = (0*(1 << w.shift - 1) + a1*(y1 + 0) +
b0*(x0 + offset) + b1*(x1 + offset))
out = p >> w.shift
y0 = min(max(0, out), (1 << w.state - 1) - 1)
logger.debug("dsp[%d,%d] p=%#x out=%#x y0=%#x",

2
artiq/gateware/test/suservo/test_servo.py
View File

@ -65,7 +65,7 @@ class ServoSim(servo.Servo):
a1, b0, b1 = coeff["a1"], coeff["b0"], coeff["b1"]
out = (
0*(1 << w.shift - 1) + # rounding
a1*(0 - y1) + b0*(offset - x0) + b1*(offset - x1)
a1*(y1 + 0) + b0*(x0 + offset) + b1*(x1 + offset)
) >> w.shift
y1 = min(max(0, out), (1 << w.state - 1) - 1)