machxo2: Improve examples directory.

machxo2/examples/README.md

@@ -10,7 +10,20 @@ This contains a simple example of running `nextpnr-machxo2`:
   using the [`iverilog`](http://iverilog.icarus.com) compiler and `vvp`
   runtime. This is known as post-place-and-route simulation.
 
-As `nextpnr-machxo2` is developed the `nextpnr` invocation in `simple.sh` and
-`simtest.sh` is subject to change. Other command invocations, such as `yosys`,
-_should_ remain unchanged, even as files under the [synth](../synth) directory
-change.
+As `nextpnr-machxo2` is developed the contents `simple.sh` and `simtest.sh`
+are subject to change.
+
+## Environment Variables For `simple.sh` And `simtest.sh`
+
+* `YOSYS`- Set to the location of the `yosys` binary to test. Defaults to the
+  `yosys` on the path. You may want to set this to a `yosys` binary in your
+  source tree if doing development.
+* `NEXTPNR`- Set to the location of the `nextpnr-machxo2` binary to test.
+  Defaults to the `nextpnr-machxo2` binary at the root of the `nextpnr` source
+  tree. This should be set, for instance, if doing an out-of-tree build of
+  `nextpnr-machxo2`.
+* `CELLS_SIM`- Set to the location of `machxo2/cells_sim.v` simulation models.
+  Defaults to whatever `yosys-config` associated with the above `YOSYS` binary
+  returns. You may want to set this to `/path/to/yosys/src/share/machxo2/cells_sim.v`
+  if doing development; `yosys-config` cannot find these "before-installation"
+  simulation models.

machxo2/examples/blinky.v

@@ -1,4 +1,4 @@
-module top(input clk, rst, output reg [7:0] leds);
+module top(input clk, rst, output [7:0] leds);
 
 reg [7:0] ctr;
 always @(posedge clk)

machxo2/examples/simple.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
 set -ex
-yosys -p "tcl ../synth/synth_machxo2.tcl 4 blinky.json" blinky.v
+${YOSYS:yosys} -p "synth_machxo2 -json blinky.json" blinky.v
 ${NEXTPNR:-../../nextpnr-machxo2} --json blinky.json --write pnrblinky.json
-yosys -p "read_verilog -lib ../synth/prims.v; read_json pnrblinky.json; dump -o blinky.il; show -format png -prefix blinky"
+${YOSYS:yosys} -p "read_verilog -lib +/machxo2/cells_sim.v; read_json pnrblinky.json; dump -o blinky.il; show -format png -prefix blinky"

machxo2/examples/simtest.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 set -ex
-yosys -p "tcl ../synth/synth_machxo2.tcl 4 blinky.json" blinky.v
+${YOSYS:-yosys} -p "synth_machxo2 -json blinky.json" blinky.v
 ${NEXTPNR:-../../nextpnr-machxo2} --no-iobs --json blinky.json --write pnrblinky.json
-yosys -p "read_json pnrblinky.json; write_verilog -noattr -norename pnrblinky.v"
-iverilog -o blinky_simtest ../synth/prims.v blinky_tb.v pnrblinky.v
+${YOSYS:-yosys} -p "read_json blinky.json; write_verilog  -noattr -norename pnrblinky.v"
+iverilog -o blinky_simtest ${CELLS_SIM:-`${YOSYS:yosys}-config --datdir/machxo2/cells_sim.v`} blinky_tb.v pnrblinky.v
 vvp -N ./blinky_simtest