feat: use nextpnr viaduct instead of python chipdb

examples/blinky/blinky.pcf

@@ -0,0 +1,6 @@
+# Pin constraints for blinky on Aegis
+# Format: set_io <signal> <bel_name>
+# IO BELs are named X<x>/Y<y>/IO<z> on the grid edges
+set_io clk   X0/Y1/IO0
+set_io reset X0/Y2/IO0
+set_io led   X0/Y3/IO0

examples/blinky/default.nix

@@ -21,7 +21,11 @@ stdenvNoCC.mkDerivation {
 
   src = lib.fileset.toSource {
     root = ./.;
-    fileset = ./blinky.v;
+    fileset = lib.fileset.unions [
+      ./blinky.v
+      ./blinky.pcf
+      ./place_io.py
+    ];
   };
 
   nativeBuildInputs = [
@@ -45,8 +49,9 @@ stdenvNoCC.mkDerivation {
     yosys -c synth.tcl > yosys.log 2>&1 || { cat yosys.log; exit 1; }
 
     echo "=== Place and route ==="
-    nextpnr-aegis-${deviceName} \
+    PCF_FILE=blinky.pcf nextpnr-aegis-${deviceName} \
       --json blinky_pnr.json \
+      --pre-place place_io.py \
       --write blinky_routed.json \
       > nextpnr.log 2>&1 || { cat nextpnr.log; echo "nextpnr finished (may have warnings)"; }
 

examples/blinky/place_io.py

@@ -0,0 +1,19 @@
+# Apply PCF-style IO constraints for Aegis
+# Reads blinky.pcf and constrains IO cells to specific BELs
+
+import os
+
+pcf_file = os.environ.get("PCF_FILE", "blinky.pcf")
+
+with open(pcf_file) as f:
+    for line in f:
+        line = line.strip()
+        if not line or line.startswith("#"):
+            continue
+        parts = line.split()
+        if len(parts) == 3 and parts[0] == "set_io":
+            signal, bel = parts[1], parts[2]
+            for cname, cell in ctx.cells:
+                if cname == signal:
+                    cell.setAttr("BEL", bel)
+                    break

flake.nix

@@ -61,6 +61,7 @@
 
           treefmt.programs = {
             black.enable = true;
+            clang-format.enable = true;
             dart-format.enable = true;
             jsonfmt.enable = true;
             nixfmt.enable = true;
@@ -73,6 +74,17 @@
             flakever = flakeverConfig;
             aegis-ip-tools = pkgs.callPackage ./pkgs/aegis-ip-tools { };
             aegis-pack = pkgs.callPackage ./pkgs/aegis-pack { inherit craneLib; };
+            nextpnr-aegis = pkgs.nextpnr.overrideAttrs (old: {
+              pname = "nextpnr-aegis";
+              postPatch = (old.postPatch or "") + ''
+                # Add Aegis viaduct uarch
+                mkdir -p generic/viaduct/aegis
+                cp ${./nextpnr-aegis/aegis.cc} generic/viaduct/aegis/aegis.cc
+
+                # Register in CMakeLists.txt
+                sed -i '/viaduct\/example\/example.cc/a\    viaduct/aegis/aegis.cc' generic/CMakeLists.txt
+              '';
+            });
             gf180mcu-pdk = pkgs.callPackage ./pkgs/gf180mcu-pdk { };
             sky130-pdk = pkgs.callPackage ./pkgs/sky130-pdk { };
           };

ip/bin/aegis_genip.dart

@@ -202,23 +202,6 @@ Future<void> main(List<String> arguments) async {
       File('$outputDir/${fpga.name}_bram.rules').writeAsStringSync(bramRules);
     }
 
-    final chipdbEmitter = ChipdbEmitter(
-      deviceName: fpga.name,
-      width: width,
-      height: height,
-      tracks: tracks,
-      serdesCount: serdesCount,
-      clockTileCount: clockTiles,
-      bramColumnInterval: bramInterval,
-      dspColumnInterval: dspInterval,
-    );
-    File(
-      '$outputDir/${fpga.name}-chipdb.py',
-    ).writeAsStringSync(chipdbEmitter.generate());
-    File(
-      '$outputDir/${fpga.name}-packer.py',
-    ).writeAsStringSync(chipdbEmitter.generatePacker());
-
     final openroadEmitter = OpenroadTclEmitter(
       moduleName: 'AegisFPGA',
       width: width,
@@ -240,7 +223,6 @@ Future<void> main(List<String> arguments) async {
     print('  $outputDir/${fpga.name}_cells.v');
     print('  $outputDir/${fpga.name}_techmap.v');
     print('  $outputDir/${fpga.name}-synth-aegis.tcl');
-    print('  $outputDir/${fpga.name}-chipdb.py');
     print('  $outputDir/${fpga.name}-openroad.tcl');
   } on FormatException catch (e) {
     print(e.message);

ip/lib/aegis_ip.dart

@@ -1,6 +1,5 @@
 export 'src/components.dart';
 export 'src/config.dart';
-export 'src/nextpnr.dart';
 export 'src/openroad.dart';
 export 'src/pdk.dart';
 export 'src/sim.dart';