[breaking-change] Add `_n` suffix to argument names of pins with fixed inverters.

Note: this change does NOT affect pin functionality or naming, and
does not require modifying your design. It does however affect some
board files, where keywords corresponding to active low pins will have
to be adjusted:
    SPIResource(0, cs="C1", ...) → SPIResource(0, cs_n="C1", ...)

The new naming scheme will make it easier to write and audit board
files by clearly marking inverted pins in resource factories, similarly to
how `PinsN` indicates the same in bare resources.

Fixes #129.

1 files changed, 3 insertions, 3 deletions

diff --git a/nmigen_boards/resources/interface.py b/nmigen_boards/resources/interface.py
index 8d5bd7e..0e0118a 100644
--- a/nmigen_boards/resources/interface.py
+++ b/nmigen_boards/resources/interface.py
@@ -56,21 +56,21 @@ def IrDAResource(number, *, rx, tx, en=None, sd=None,
     return Resource("irda", number, *io)
 
 
-def SPIResource(*args, cs, clk, copi, cipo, int=None, reset=None,
+def SPIResource(*args, cs_n, clk, copi, cipo, int=None, reset=None,
                 conn=None, attrs=None, role="controller"):
     assert role in ("controller", "peripheral")
     assert copi is not None or cipo is not None # support unidirectional SPI
 
     io = []
     if role == "controller":
-        io.append(Subsignal("cs", PinsN(cs, dir="o", conn=conn)))
+        io.append(Subsignal("cs", PinsN(cs_n, dir="o", conn=conn)))
         io.append(Subsignal("clk", Pins(clk, dir="o", conn=conn, assert_width=1)))
         if copi is not None:
             io.append(Subsignal("copi", Pins(copi, dir="o", conn=conn, assert_width=1)))
         if cipo is not None:
             io.append(Subsignal("cipo", Pins(cipo, dir="i", conn=conn, assert_width=1)))
     else:  # peripheral
-        io.append(Subsignal("cs", PinsN(cs, dir="i", conn=conn, assert_width=1)))
+        io.append(Subsignal("cs", PinsN(cs_n, dir="i", conn=conn, assert_width=1)))
         io.append(Subsignal("clk", Pins(clk, dir="i", conn=conn, assert_width=1)))
         if copi is not None:
             io.append(Subsignal("copi", Pins(copi, dir="i", conn=conn, assert_width=1)))