generic/examples: Add FASM writer Python script

Signed-off-by: David Shah <dave@ds0.me>

generic/examples/.gitignore

@@ -1 +1,3 @@
-blinky.txt
+blinky.fasm
+__pycache__
+*.pyc

generic/examples/README.md

@@ -7,7 +7,8 @@ This contains a simple, artificial, example of the nextpnr generic API.
  
  - simple_timing.py annotates cells with timing data (this is a separate script that must be run after packing)
 
- - report.py stores design information after place-and-route to blinky.txt in place
-   of real bitstream generation
+ - write_fasm.py uses the nextpnr Python API to write a FASM file for a design
+
+ - bitstream.py uses write_fasm.py to create a FASM ("FPGA assembly") file for the place-and-routed design
 
  - Run simple.sh to build an example design on the FPGA above

generic/examples/bitstream.py

@@ -0,0 +1,17 @@
+from write_fasm import *
+from simple_config import K
+
+# Need to tell FASM generator how to write parameters
+# (celltype, parameter) -> ParameterConfig
+param_map = {
+	("GENERIC_SLICE", "K"): ParameterConfig(write=False),
+	("GENERIC_SLICE", "INIT"): ParameterConfig(write=True, numeric=True, width=2**K),
+	("GENERIC_SLICE", "FF_USED"): ParameterConfig(write=True, numeric=True, width=1),
+
+	("GENERIC_IOB", "INPUT_USED"): ParameterConfig(write=True, numeric=True, width=1),
+	("GENERIC_IOB", "OUTPUT_USED"): ParameterConfig(write=True, numeric=True, width=1),
+	("GENERIC_IOB", "ENABLE_USED"): ParameterConfig(write=True, numeric=True, width=1),
+}
+
+with open("blinky.fasm", "w") as f:
+	write_fasm(ctx, param_map, f)

generic/examples/report.py

@@ -1,13 +0,0 @@
-with open("blinky.txt", "w") as f:
-	for nname, net in ctx.nets:
-		print("# Net %s" % nname, file=f)
-		# FIXME: Pip ordering
-		for wire, pip in net.wires:
-			if pip.pip != "":
-				print("%s" % pip.pip, file=f)
-		print("", file=f)
-	for cname, cell in ctx.cells:
-		print("# Cell %s at %s" % (cname, cell.bel), file=f)
-		for param, val in cell.params:
-			print("%s.%s %s" % (cell.bel, param, val), file=f)
-		print("", file=f)

generic/examples/simple.py

@@ -1,22 +1,4 @@
-# Grid size including IOBs at edges
-X = 12
-Y = 12
-# SLICEs per tile
-N = 8
-# LUT input count
-K = 4
-# Number of local wires
-Wl = N*(K+1) + 8 
-# 1/Fc for bel input wire pips
-Si = 4
-# 1/Fc for Q to local wire pips
-Sq = 4
-# ~1/Fc local to neighbour local wire pips
-Sl = 8
-
-# Create graphic elements
-# Bels
-ctx.addDecalGraphic("bel", GraphicElement(type=TYPE_BOX, style=STYLE_INACTIVE, x1=0, y1=0, x2=0.2, y2=(1/(N+1))-0.02, z=0))
+from simple_config import *
 
 def is_io(x, y):
 	return x == 0 or x == X-1 or y == 0 or y == Y-1
@@ -41,7 +23,6 @@ for x in range(X):
 				ctx.addBelInput(bel="X%dY%d_IO%d" % (x, y, z), name="I", wire="X%dY%dZ%d_I0" % (x, y, z))
 				ctx.addBelInput(bel="X%dY%d_IO%d" % (x, y, z), name="EN", wire="X%dY%dZ%d_I1" % (x, y, z))
 				ctx.addBelOutput(bel="X%dY%d_IO%d" % (x, y, z), name="O", wire="X%dY%dZ%d_Q" % (x, y, z))
-				ctx.setBelDecal(bel="X%dY%d_IO%d" % (x, y, z), decalxy=ctx.DecalXY("bel", 0.6, z * (1/(N+1))))
 		else:
 			for z in range(N):
 				ctx.addBel(name="X%dY%d_SLICE%d" % (x, y, z), type="GENERIC_SLICE", loc=Loc(x, y, z), gb=False)
@@ -49,7 +30,6 @@ for x in range(X):
 				for k in range(K):
 					ctx.addBelInput(bel="X%dY%d_SLICE%d" % (x, y, z), name="I[%d]" % k, wire="X%dY%dZ%d_I%d" % (x, y, z, k))
 				ctx.addBelOutput(bel="X%dY%d_SLICE%d" % (x, y, z), name="Q", wire="X%dY%dZ%d_Q" % (x, y, z))
-				ctx.setBelDecal(bel="X%dY%d_SLICE%d" % (x, y, z), decalxy=ctx.DecalXY("bel", 0.6, z * (1/(N+1))))
 
 for x in range(X):
 	for y in range(Y):

generic/examples/simple.sh

@@ -1,4 +1,4 @@
 #!/usr/bin/bash
 set -ex
 yosys -p "tcl ../synth/synth_generic.tcl 4 blinky.json" blinky.v
-../../nextpnr-generic --pre-pack simple.py --pre-place simple_timing.py --json blinky.json --post-route report.py
+../../nextpnr-generic --pre-pack simple.py --pre-place simple_timing.py --json blinky.json --post-route bitstream.py

generic/examples/simple_config.py

@@ -0,0 +1,15 @@
+# Grid size including IOBs at edges
+X = 12
+Y = 12
+# SLICEs per tile
+N = 8
+# LUT input count
+K = 4
+# Number of local wires
+Wl = N*(K+1) + 8 
+# 1/Fc for bel input wire pips
+Si = 4
+# 1/Fc for Q to local wire pips
+Sq = 4
+# ~1/Fc local to neighbour local wire pips
+Sl = 8

generic/examples/write_fasm.py

@@ -0,0 +1,52 @@
+from collections import namedtuple
+
+"""
+	write:   set to True to enable writing this parameter to FASM
+
+	numeric: set to True to write this parameter as a bit array (width>1) or
+	         single bit (width==1) named after the parameter. Otherwise this
+	         parameter will be written as `name.value`
+
+	width:   width of numeric parameter (ignored for non-numeric parameters)
+	
+	alias:   an alternative name for this parameter (parameter name used if alias
+	         is None)
+"""
+ParameterConfig = namedtuple('ParameterConfig', 'write numeric width alias')
+
+# FIXME use defaults= once Python 3.7 is standard
+ParameterConfig.__new__.__defaults__ = (False, True, 1, None)
+
+
+"""
+Write a design as FASM
+
+    ctx:      nextpnr context
+    paramCfg: ParameterConfig describing how to write parameters
+    f:        output file
+"""
+def write_fasm(ctx, paramCfg, f):
+	for nname, net in sorted(ctx.nets, key=lambda x: str(x[1].name)):
+		print("# Net %s" % nname, file=f)
+		for wire, pip in sorted(net.wires, key=lambda x: str(x[1])):
+			if pip.pip != "":
+				print("%s" % pip.pip, file=f)
+		print("", file=f)
+	for cname, cell in sorted(ctx.cells, key=lambda x: str(x[1].name)):
+		print("# Cell %s at %s" % (cname, cell.bel), file=f)
+		for param, val in sorted(cell.params, key=lambda x: str(x)):
+			cfg = paramCfg[(cell.type, param)]
+			if not cfg.write:
+				continue
+			fasm_name = cfg.alias if cfg.alias is not None else param
+			if cfg.numeric:
+				if cfg.width == 1:
+					if int(val) != 0:
+						print("%s.%s" % (cell.bel, fasm_name), file=f)
+				else:
+					# Parameters with width >32 are direct binary, otherwise denary
+					binval = val if cfg.width > 32 else "{:0{}b}".format(int(val), cfg.width)
+					print("%s.%s[%d:0] = %d'b%s" % (cell.bel, fasm_name, cfg.width-1, cfg.width, binval), file=f)
+			else:
+				print("%s.%s.%s" % (cell.bel, fasm_name, val), file=f)
+		print("", file=f)