diff --git a/docs/index.html b/docs/index.html
index 7e718e7..35fd2ec 100644
--- a/docs/index.html
+++ b/docs/index.html
@@ -75,37 +75,37 @@
 </p>
 
 <table class="ctab">
-<tr><th>Part</th><th>Package</th><th>Pin Spacing</th><th>I/Os</th><th>arachne-pnr opts</th><th>icetime opts</th></tr>
-<tr><td>iCE40-LP1K-SWG16TR</td><td>16-ball WLCSP (1.40 x 1.48 mm)</td><td>0.35 mm</td><td>10</td><td>-d 1k -P swg16tr</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-UP3K-UWG30</td><td>30-ball WLCSP (2.15 x 2.55 mm)</td><td>0.40 mm</td><td>21</td><td>-d 5k -P uwg30</td><td>-d up5k</td></tr>
-<tr><td>iCE40-UP5K-UWG30</td><td>30-ball WLCSP (2.15 x 2.55 mm)</td><td>0.40 mm</td><td>21</td><td>-d 5k -P uwg30</td><td>-d up5k</td></tr>
-<tr><td>iCE40-LP384-CM36</td><td>36-ball ucBGA (2.5 x 2.5 mm)</td><td>0.40 mm</td><td>25</td><td>-d 384 -P cm36</td><td>-d lp384</td></tr>
-<tr><td>iCE40-LP1K-CM36</td><td>36-ball ucBGA (2.5 x 2.5 mm)</td><td>0.40 mm</td><td>25</td><td>-d 1k -P cm36</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP384-CM49</td><td>49-ball ucBGA (3 x 3 mm)</td><td>0.40 mm</td><td>37</td><td>-d 384 -P cm49</td><td>-d lp384</td></tr>
-<tr><td>iCE40-LP1K-CM49</td><td>49-ball ucBGA (3 x 3 mm)</td><td>0.40 mm</td><td>35</td><td>-d 1k -P cm49</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP1K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>-d 1k -P cm81</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP4K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>-d 8k -P cm81:4k</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-LP8K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>-d 8k -P cm81</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-LP1K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>95</td><td>-d 1k -P cm121</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP4K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>93</td><td>-d 8k -P cm121:4k</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-LP8K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>93</td><td>-d 8k -P cm121</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-LP4K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>167</td><td>-d 8k -P cm225:4k</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-LP8K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>178</td><td>-d 8k -P cm225</td><td>-d lp8k</td></tr>
-<tr><td>iCE40-HX8K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>178</td><td>-d 8k -P cm225</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-LP384-QN32</td><td>32-pin QFN (5 x 5 mm)</td><td>0.50 mm</td><td>21</td><td>-d 384 -P qn32</td><td>-d lp384</td></tr>
-<tr><td>iCE40-UP5K-SG48</td><td>48-pin QFN (7 x 7 mm)</td><td>0.50 mm</td><td>39</td><td>-d 5k -P sg48</td><td>-d up5k</td></tr>
-<tr><td>iCE40-LP1K-QN84</td><td>84-pin QFNS (7 x 7 mm)</td><td>0.50 mm</td><td>67</td><td>-d 1k -P qn84</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP1K-CB81</td><td>81-ball csBGA (5 x 5 mm)</td><td>0.50 mm</td><td>62</td><td>-d 1k -P cb81</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-LP1K-CB121</td><td>121-ball csBGA (6 x 6 mm)</td><td>0.50 mm</td><td>92</td><td>-d 1k -P cb121</td><td>-d lp1k</td></tr>
-<tr><td>iCE40-HX1K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>-d 1k -P cb132</td><td>-d hx1k</td></tr>
-<tr><td>iCE40-HX4K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>-d 8k -P cb132:4k</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-HX8K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>-d 8k -P cb132</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-HX1K-VQ100</td><td>100-pin VQFP (14 x 14 mm)</td><td>0.50 mm</td><td>72</td><td>-d 1k -P vq100</td><td>-d hx1k</td></tr>
-<tr><td>iCE40-HX1K-TQ144</td><td>144-pin TQFP (20 x 20 mm)</td><td>0.50 mm</td><td>96</td><td>-d 1k -P tq144</td><td>-d hx1k</td></tr>
-<tr><td>iCE40-HX4K-TQ144</td><td>144-pin TQFP (20 x 20 mm)</td><td>0.50 mm</td><td>107</td><td>-d 8k -P tq144:4k</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-HX4K-BG121</td><td>121-ball caBGA (9 x 9 mm)</td><td>0.80 mm</td><td>93</td><td>-d 8k -P bg121:4k</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-HX8K-BG121</td><td>121-ball caBGA (9 x 9 mm)</td><td>0.80 mm</td><td>93</td><td>-d 8k -P bg121</td><td>-d hx8k</td></tr>
-<tr><td>iCE40-HX8K-CT256</td><td>256-ball caBGA (14 x 14 mm)</td><td>0.80 mm</td><td>206</td><td>-d 8k -P ct256</td><td>-d hx8k</td></tr>
+<tr><th>Part</th><th>Package</th><th>Pin Spacing</th><th>I/Os</th><th>nextpnr opts</th><th>arachne-pnr opts</th><th>icetime opts</th></tr>
+<tr><td>iCE40-LP1K-SWG16TR</td><td>16-ball WLCSP (1.40 x 1.48 mm)</td><td>0.35 mm</td><td>10</td><td>--lp1k --package swg16tr</td><td>-d 1k -P swg16tr</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-UP3K-UWG30</td><td>30-ball WLCSP (2.15 x 2.55 mm)</td><td>0.40 mm</td><td>21</td><td>--up5k --package uwg30</td><td>-d 5k -P uwg30</td><td>-d up5k</td></tr>
+<tr><td>iCE40-UP5K-UWG30</td><td>30-ball WLCSP (2.15 x 2.55 mm)</td><td>0.40 mm</td><td>21</td><td>--up5k --package uwg30</td><td>-d 5k -P uwg30</td><td>-d up5k</td></tr>
+<tr><td>iCE40-LP384-CM36</td><td>36-ball ucBGA (2.5 x 2.5 mm)</td><td>0.40 mm</td><td>25</td><td>--lp384 --package cm36</td><td>-d 384 -P cm36</td><td>-d lp384</td></tr>
+<tr><td>iCE40-LP1K-CM36</td><td>36-ball ucBGA (2.5 x 2.5 mm)</td><td>0.40 mm</td><td>25</td><td>--lp1k --package cm36</td><td>-d 1k -P cm36</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP384-CM49</td><td>49-ball ucBGA (3 x 3 mm)</td><td>0.40 mm</td><td>37</td><td>--lp384 --package cm49</td><td>-d 384 -P cm49</td><td>-d lp384</td></tr>
+<tr><td>iCE40-LP1K-CM49</td><td>49-ball ucBGA (3 x 3 mm)</td><td>0.40 mm</td><td>35</td><td>--lp1k --package cm49</td><td>-d 1k -P cm49</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP1K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>--lp1k --package cm81</td><td>-d 1k -P cm81</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP4K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>--lp8k --package cm81:4k</td><td>-d 8k -P cm81:4k</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-LP8K-CM81</td><td>81-ball ucBGA (4 x 4 mm)</td><td>0.40 mm</td><td>63</td><td>--lp9k --package cm81</td><td>-d 8k -P cm81</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-LP1K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>95</td><td>--lp1k --package cm121</td><td>-d 1k -P cm121</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP4K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>93</td><td>--lp8k --package cm121:4k</td><td>-d 8k -P cm121:4k</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-LP8K-CM121</td><td>121-ball ucBGA (5 x 5 mm)</td><td>0.40 mm</td><td>93</td><td>--lp8k --package cm121</td><td>-d 8k -P cm121</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-LP4K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>167</td><td>--lp8k --package cm225:4k</td><td>-d 8k -P cm225:4k</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-LP8K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>178</td><td>--lp8k --package cm225</td><td>-d 8k -P cm225</td><td>-d lp8k</td></tr>
+<tr><td>iCE40-HX8K-CM225</td><td>225-ball ucBGA (7 x 7 mm)</td><td>0.40 mm</td><td>178</td><td>--hx8k --package cm225</td><td>-d 8k -P cm225</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-LP384-QN32</td><td>32-pin QFN (5 x 5 mm)</td><td>0.50 mm</td><td>21</td><td>--lp384 --package qn32</td><td>-d 384 -P qn32</td><td>-d lp384</td></tr>
+<tr><td>iCE40-UP5K-SG48</td><td>48-pin QFN (7 x 7 mm)</td><td>0.50 mm</td><td>39</td><td>--up5k --package sg48</td><td>-d 5k -P sg48</td><td>-d up5k</td></tr>
+<tr><td>iCE40-LP1K-QN84</td><td>84-pin QFNS (7 x 7 mm)</td><td>0.50 mm</td><td>67</td><td>--lp1k --package qn84</td><td>-d 1k -P qn84</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP1K-CB81</td><td>81-ball csBGA (5 x 5 mm)</td><td>0.50 mm</td><td>62</td><td>--lp1k --package cb81</td><td>-d 1k -P cb81</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-LP1K-CB121</td><td>121-ball csBGA (6 x 6 mm)</td><td>0.50 mm</td><td>92</td><td>--lp1k --package cb121</td><td>-d 1k -P cb121</td><td>-d lp1k</td></tr>
+<tr><td>iCE40-HX1K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>--hx1k --package cb132</td><td>-d 1k -P cb132</td><td>-d hx1k</td></tr>
+<tr><td>iCE40-HX4K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>--hx8k --package cb132:4k</td><td>-d 8k -P cb132:4k</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-HX8K-CB132</td><td>132-ball csBGA (8 x 8 mm)</td><td>0.50 mm</td><td>95</td><td>--hx8k --package cb132</td><td>-d 8k -P cb132</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-HX1K-VQ100</td><td>100-pin VQFP (14 x 14 mm)</td><td>0.50 mm</td><td>72</td><td>--hx1k --package vq100</td><td>-d 1k -P vq100</td><td>-d hx1k</td></tr>
+<tr><td>iCE40-HX1K-TQ144</td><td>144-pin TQFP (20 x 20 mm)</td><td>0.50 mm</td><td>96</td><td>--hx1k --package tq144</td><td>-d 1k -P tq144</td><td>-d hx1k</td></tr>
+<tr><td>iCE40-HX4K-TQ144</td><td>144-pin TQFP (20 x 20 mm)</td><td>0.50 mm</td><td>107</td><td>--hx8k --package tq144:4k</td><td>-d 8k -P tq144:4k</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-HX4K-BG121</td><td>121-ball caBGA (9 x 9 mm)</td><td>0.80 mm</td><td>93</td><td>--hx8k --package bg121:4k</td><td>-d 8k -P bg121:4k</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-HX8K-BG121</td><td>121-ball caBGA (9 x 9 mm)</td><td>0.80 mm</td><td>93</td><td>--hx8k --package bg121</td><td>-d 8k -P bg121</td><td>-d hx8k</td></tr>
+<tr><td>iCE40-HX8K-CT256</td><td>256-ball caBGA (14 x 14 mm)</td><td>0.80 mm</td><td>206</td><td>--hx8k --package ct256</td><td>-d 8k -P ct256</td><td>-d hx8k</td></tr>
 </table>
 
 <p>
@@ -143,7 +143,7 @@
 sudo apt-get install build-essential clang bison flex libreadline-dev \
                      gawk tcl-dev libffi-dev git mercurial graphviz   \
                      xdot pkg-config python python3 libftdi-dev \
-                     qt5-default python3-dev libboost-dev
+                     qt5-default python3-dev libboost-all-dev cmake
 </pre>
 
 <p>
diff --git a/examples/icestick/Makefile b/examples/icestick/Makefile
index 8b8e741..58f26b9 100644
--- a/examples/icestick/Makefile
+++ b/examples/icestick/Makefile
@@ -34,6 +34,10 @@
 %_syntb.vcd: %_syntb
 	vvp -N $< +vcd=$@
 
+sim: $(PROJ)_tb.vcd
+
+postsim: $(PROJ)_syntb.vcd
+
 prog: $(PROJ).bin
 	iceprog $<
 
diff --git a/examples/icestick/rs232demo.v b/examples/icestick/rs232demo.v
index 40347e8..9f66f97 100644
--- a/examples/icestick/rs232demo.v
+++ b/examples/icestick/rs232demo.v
@@ -1,17 +1,59 @@
+// A simple design demonstrating receiving and sending of RS232 signals
+//
+// With this design loaded, connect with a serial terminal to the USB serial
+// port of the icestick (with 9600 BAUD) and use the number keys 1..5 to toggle
+// the LEDs.
+
 module top (
 	input  clk,
 	input  RX,
 	output TX,
+	output LED1,
+	output LED2,
+	output LED3,
+	output LED4,
+	output LED5
+);
+	parameter integer BAUD_RATE = 9600;
+	parameter integer CLOCK_FREQ_HZ = 12000000;
+	localparam integer PERIOD = CLOCK_FREQ_HZ / BAUD_RATE;
+
+	rs232_recv #(
+		.HALF_PERIOD(PERIOD / 2)
+	) recv (
+		.clk  (clk ),
+		.RX   (RX  ),
+		.LED1 (LED1),
+		.LED2 (LED2),
+		.LED3 (LED3),
+		.LED4 (LED4),
+		.LED5 (LED5)
+	);
+
+	rs232_send #(
+		.PERIOD(PERIOD)
+	) send (
+		.clk  (clk ),
+		.TX   (TX  ),
+		.LED1 (LED1),
+		.LED2 (LED2),
+		.LED3 (LED3),
+		.LED4 (LED4),
+		.LED5 (LED5)
+	);
+endmodule
+
+module rs232_recv #(
+	parameter integer HALF_PERIOD = 5
+) (
+	input  clk,
+	input  RX,
 	output reg LED1,
 	output reg LED2,
 	output reg LED3,
 	output reg LED4,
 	output reg LED5
 );
-	parameter integer BAUD_RATE = 9600;
-	parameter integer CLOCK_FREQ_HZ = 12000000;
-	localparam integer HALF_PERIOD = CLOCK_FREQ_HZ / (2 * BAUD_RATE);
-
 	reg [7:0] buffer;
 	reg buffer_valid;
 
@@ -20,11 +62,11 @@
 	reg recv = 0;
 
 	initial begin
-		LED1 = 0;
+		LED1 = 1;
 		LED2 = 0;
-		LED3 = 0;
+		LED3 = 1;
 		LED4 = 0;
-		LED5 = 0;
+		LED5 = 1;
 	end
 
 	always @(posedge clk) begin
@@ -60,6 +102,72 @@
 			if (buffer == "5") LED5 <= !LED5;
 		end
 	end
+endmodule
 
-	assign TX = RX;
+module rs232_send #(
+	parameter integer PERIOD = 10
+) (
+	input  clk,
+	output TX,
+	input  LED1,
+	input  LED2,
+	input  LED3,
+	input  LED4,
+	input  LED5
+);
+	reg [7:0] buffer;
+	reg buffer_valid;
+
+	reg [$clog2(PERIOD):0] cycle_cnt = 0;
+	reg [4:0] bit_cnt = 0;
+	reg [5:0] byte_cnt = 60;
+
+	always @(posedge clk) begin
+		cycle_cnt <= cycle_cnt + 1;
+		if (cycle_cnt == PERIOD-1) begin
+			cycle_cnt <= 0;
+			bit_cnt <= bit_cnt + 1;
+			if (bit_cnt == 10) begin
+				bit_cnt <= 0;
+				byte_cnt <= byte_cnt + 1;
+			end
+		end
+	end
+
+	reg [7:0] data_byte;
+	reg data_bit;
+
+	always @* begin
+		data_byte = 'bx;
+		case (byte_cnt)
+			0: data_byte <= "\r";
+			1: data_byte <= LED1 ? "*" : "-";
+			2: data_byte <= LED2 ? "*" : "-";
+			3: data_byte <= LED3 ? "*" : "-";
+			4: data_byte <= LED4 ? "*" : "-";
+			5: data_byte <= LED5 ? "*" : "-";
+		endcase
+	end
+
+	always @(posedge clk) begin
+		data_bit = 'bx;
+		case (bit_cnt)
+			0: data_bit <= 0; // start bit
+			1: data_bit <= data_byte[0];
+			2: data_bit <= data_byte[1];
+			3: data_bit <= data_byte[2];
+			4: data_bit <= data_byte[3];
+			5: data_bit <= data_byte[4];
+			6: data_bit <= data_byte[5];
+			7: data_bit <= data_byte[6];
+			8: data_bit <= data_byte[7];
+			9: data_bit <= 1;  // stop bit
+			10: data_bit <= 1; // stop bit
+		endcase
+		if (byte_cnt > 5) begin
+			data_bit <= 1;
+		end
+	end
+
+	assign TX = data_bit;
 endmodule
diff --git a/examples/icestick/rs232demo_tb.v b/examples/icestick/rs232demo_tb.v
index 5b9aee1..fd3a0cf 100644
--- a/examples/icestick/rs232demo_tb.v
+++ b/examples/icestick/rs232demo_tb.v
@@ -53,6 +53,11 @@
 
 		repeat (10 * PERIOD) @(posedge clk);
 
+		// turn all LEDs off
+		send_byte("1");
+		send_byte("3");
+		send_byte("5");
+
 		// turn all LEDs on
 		send_byte("1");
 		send_byte("2");