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Wrong number of pins reported when the direction is "io" #397

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jeanthom opened this issue Jun 3, 2020 · 3 comments
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Wrong number of pins reported when the direction is "io" #397

jeanthom opened this issue Jun 3, 2020 · 3 comments
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@jeanthom
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jeanthom commented Jun 3, 2020

Hi,

I just came across a bug that causes nMigen to report the wrong number of pins when the direction of the pins is set to bidirectional.

Test code:

from nmigen import *
from nmigen_boards.arty_a7 import ArtyA7Platform

platform = ArtyA7Platform()
ram = platform.request("ddr3", 0)

print("Number of DQ signals:", len(ram.dq)) # DQ is "io"
print("Number of A signals:", len(ram.a)) # A is output only

Result:

Number of DQ signals: 33
Number of A signals: 14

What I was expecting:

Number of DQ signals: 16
Number of A signals: 14
@whitequark
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You should never use attributes of the object returned by platform.request directly. Instead, use ram.x.i for inputs or inouts, ram.x.o for outputs or inouts, and ram.x.oe for inouts.

@jeanthom
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jeanthom commented Jun 3, 2020

Ok, I will use .i/.o/.oe instead.

@jeanthom jeanthom closed this as completed Jun 3, 2020
@whitequark
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FWIW, this is a footgun I'm aware of and I have plans to fix it.

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@whitequark @jeanthom