Implement working serial repl

6 files changed, 667 insertions, 28 deletions

diff --git a/atk16_fpga/.gitignore b/atk16_fpga/.gitignore
index bba1e09..5fdef91 100644
--- a/atk16_fpga/.gitignore
+++ b/atk16_fpga/.gitignore
@@ -4,3 +4,4 @@
 *.out
 *.vcd
 *.dblite
+data_strings.v
diff --git a/atk16_fpga/Makefile b/atk16_fpga/Makefile
index cada068..2a7e495 100644
--- a/atk16_fpga/Makefile
+++ b/atk16_fpga/Makefile
@@ -1,6 +1,9 @@
 BIN ?= program.bin
 
-hardware.bin: top.v
+data_strings.v: gen_data_strings_v.py
+	python gen_data_strings_v.py > data_strings.v
+
+hardware.bin: top.v data_strings.v
 	apio verify
 	apio test
 	apio build
diff --git a/atk16_fpga/gen_data_strings_v.py b/atk16_fpga/gen_data_strings_v.py
new file mode 100755
index 0000000..afb374e
--- /dev/null
+++ b/atk16_fpga/gen_data_strings_v.py
@@ -0,0 +1,25 @@
+#!/usr/bin/env python
+
+def gen(name, message):
+    for line in message.split('\n'):
+        print(f'// {line}')
+
+    print(f"`define LEN_{name} {len(message)}")
+    print(f"`define STR_{name} \\")
+    print(f"    reg [7:0] str_{name} [0:`LEN_{name}-1]; \\")
+    print(f"    initial begin \\")
+    for i, c in enumerate(message):
+        print(f"        str_{name}[{i}] = 8'd{ord(c)}; \\")
+
+    print(f"    end")
+    print("")
+
+gen("welcome", "Welcome to the ATK16 serial programmer. Press 'h' for help.\n")
+gen("help",
+    "Help:\n" +
+    "    h - help\n" +
+    "    p - program\n"
+)
+gen("program_ready",
+    "Ready to receive program data. Reset device after transmission.\n"
+)
diff --git a/atk16_fpga/hardware.dot b/atk16_fpga/hardware.dot
new file mode 100644
index 0000000..e1f4c58
--- /dev/null
+++ b/atk16_fpga/hardware.dot
@@ -0,0 +1,70 @@
+digraph "top" {
+label="top";
+rankdir="LR";
+remincross=true;
+n13 [ shape=diamond, label="rx_done", color="black", fontcolor="black" ];
+n14 [ shape=diamond, label="data_to_receive", color="black", fontcolor="black" ];
+n15 [ shape=diamond, label="state", color="black", fontcolor="black" ];
+n16 [ shape=diamond, label="letter_a", color="black", fontcolor="black" ];
+n17 [ shape=diamond, label="tx_busy", color="black", fontcolor="black" ];
+n18 [ shape=diamond, label="data_to_send", color="black", fontcolor="black" ];
+n19 [ shape=diamond, label="start_tx", color="black", fontcolor="black" ];
+n20 [ shape=octagon, label="LED2", color="black", fontcolor="black" ];
+n21 [ shape=octagon, label="LED1", color="black", fontcolor="black" ];
+n22 [ shape=octagon, label="SERIAL_TX", color="black", fontcolor="black" ];
+n23 [ shape=octagon, label="SERIAL_RX", color="black", fontcolor="black" ];
+n24 [ shape=octagon, label="SYSCLK", color="black", fontcolor="black" ];
+v0 [ label="1" ];
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+c35 [ shape=record, label="{{<p31> clk|<p32> data|<p33> done|<p34> rx}|uart_rx_inst\nuart_rx|{}}",  ];
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+}
diff --git a/atk16_fpga/hardware.svg b/atk16_fpga/hardware.svg
new file mode 100644
index 0000000..66b633e
--- /dev/null
+++ b/atk16_fpga/hardware.svg
@@ -0,0 +1,463 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
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+ -->
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+<polyline fill="none" stroke="black" points="287.12,-121 287.12,-162"/>
+<text text-anchor="middle" x="300" y="-136.7" font-family="Times,serif" font-size="14.00">Y</text>
+</g>
+<!-- n17&#45;&gt;c40 -->
+<g id="edge13" class="edge">
+<title>n17:e&#45;&gt;c40:w</title>
+<path fill="none" stroke="#1b9e77" d="M116.29,-141.5C143.4,-141.5 152.87,-141.69 175.3,-141.74"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="175.1,-145.24 185.11,-141.75 175.11,-138.24 175.1,-145.24"/>
+</g>
+<!-- c41 -->
+<g id="node20" class="node">
+<title>c41</title>
+<polygon fill="none" stroke="black" points="187.62,-181 187.62,-222 312.87,-222 312.87,-181 187.62,-181"/>
+<text text-anchor="middle" x="200.5" y="-196.7" font-family="Times,serif" font-size="14.00">A</text>
+<polyline fill="none" stroke="black" points="213.37,-181 213.37,-222"/>
+<text text-anchor="middle" x="250.25" y="-204.7" font-family="Times,serif" font-size="14.00">$3</text>
+<text text-anchor="middle" x="250.25" y="-188.2" font-family="Times,serif" font-size="14.00">$logic_not</text>
+<polyline fill="none" stroke="black" points="287.12,-181 287.12,-222"/>
+<text text-anchor="middle" x="300" y="-196.7" font-family="Times,serif" font-size="14.00">Y</text>
+</g>
+<!-- n17&#45;&gt;c41 -->
+<g id="edge14" class="edge">
+<title>n17:e&#45;&gt;c41:w</title>
+<path fill="none" stroke="#1b9e77" d="M116.29,-141.5C153.27,-141.5 147.35,-190.13 175.61,-200.01"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="174.7,-203.41 185.13,-201.51 175.79,-196.5 174.7,-203.41"/>
+</g>
+<!-- n18 -->
+<g id="node6" class="node">
+<title>n18</title>
+<polygon fill="none" stroke="black" points="647.65,-246.5 563.45,-228.5 647.65,-210.5 731.86,-228.5 647.65,-246.5"/>
+<text text-anchor="middle" x="647.65" y="-223.45" font-family="Times,serif" font-size="14.00">data_to_send</text>
+</g>
+<!-- n18&#45;&gt;c39 -->
+<g id="edge17" class="edge">
+<title>n18:e&#45;&gt;c39:w</title>
+<path fill="none" stroke="#1b9e77" stroke-width="3" d="M731.86,-228.5C747.97,-228.5 748.23,-210.55 757.16,-202.42"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" stroke-width="3" points="755.41,-206.79 763.59,-200.06 753,-200.22 755.41,-206.79"/>
+</g>
+<!-- n18&#45;&gt;p6 -->
+<g id="edge18" class="edge">
+<title>n18:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#1b9e77" stroke-width="3" d="M734.95,-228.5C742.97,-228.5 739.61,-240.83 733.95,-246.5 720.56,-259.94 582.08,-252.87 563.45,-256.5 536.91,-261.67 532.51,-271.61 505.83,-276 483.9,-279.61 421.92,-291.33 405.83,-276 403.14,-273.44 400.97,-269.58 399.95,-265.9"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" stroke-width="3" points="401.82,-270.15 402.9,-259.61 395.48,-267.17 401.82,-270.15"/>
+</g>
+<!-- n19 -->
+<g id="node7" class="node">
+<title>n19</title>
+<polygon fill="none" stroke="black" points="647.65,-192.5 593.13,-174.5 647.65,-156.5 702.18,-174.5 647.65,-192.5"/>
+<text text-anchor="middle" x="647.65" y="-169.45" font-family="Times,serif" font-size="14.00">start_tx</text>
+</g>
+<!-- n19&#45;&gt;c39 -->
+<g id="edge21" class="edge">
+<title>n19:e&#45;&gt;c39:w</title>
+<path fill="none" stroke="#e6ab02" d="M704.54,-174.5C728.5,-174.5 737.16,-174.14 756.58,-174.03"/>
+<polygon fill="#e6ab02" stroke="#e6ab02" points="756.35,-177.53 766.34,-174 756.33,-170.53 756.35,-177.53"/>
+</g>
+<!-- n19&#45;&gt;p6 -->
+<g id="edge22" class="edge">
+<title>n19:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#e6ab02" d="M704.54,-174.5C712.55,-174.5 709.18,-186.81 703.54,-192.5 681.58,-214.65 591,-186.87 563.45,-201.5 526.48,-221.14 543.41,-257.56 505.83,-276 485.88,-285.79 421.92,-291.33 405.83,-276 403.14,-273.44 400.97,-269.58 399.95,-265.9"/>
+<polygon fill="#e6ab02" stroke="#e6ab02" points="403.1,-267.41 404.18,-256.87 396.77,-264.43 403.1,-267.41"/>
+</g>
+<!-- n20 -->
+<g id="node8" class="node">
+<title>n20</title>
+<polygon fill="none" stroke="black" points="1148.73,-614.04 1148.73,-628.96 1127.53,-639.5 1097.54,-639.5 1076.34,-628.96 1076.34,-614.04 1097.54,-603.5 1127.53,-603.5 1148.73,-614.04"/>
+<text text-anchor="middle" x="1112.54" y="-616.45" font-family="Times,serif" font-size="14.00">LED2</text>
+</g>
+<!-- n21 -->
+<g id="node9" class="node">
+<title>n21</title>
+<polygon fill="none" stroke="black" points="1000.74,-614.04 1000.74,-628.96 979.54,-639.5 949.56,-639.5 928.36,-628.96 928.36,-614.04 949.56,-603.5 979.54,-603.5 1000.74,-614.04"/>
+<text text-anchor="middle" x="964.55" y="-616.45" font-family="Times,serif" font-size="14.00">LED1</text>
+</g>
+<!-- x8 -->
+<g id="node28" class="node">
+<title>x8</title>
+<ellipse fill="black" stroke="black" cx="1038.54" cy="-621.5" rx="1.8" ry="1.8"/>
+</g>
+<!-- n21&#45;&gt;x8 -->
+<g id="edge25" class="edge">
+<title>n21:e&#45;&gt;x8:w</title>
+<path fill="none" stroke="#d95f02" d="M1000.74,-621.5C1012.12,-621.5 1017.43,-621.5 1025.3,-621.5"/>
+<polygon fill="#d95f02" stroke="#d95f02" points="1025.23,-625 1035.23,-621.5 1025.23,-618 1025.23,-625"/>
+</g>
+<!-- n22 -->
+<g id="node10" class="node">
+<title>n22</title>
+<polygon fill="none" stroke="black" points="712.65,-35.04 712.65,-49.96 674.58,-60.5 620.73,-60.5 582.65,-49.96 582.65,-35.04 620.73,-24.5 674.58,-24.5 712.65,-35.04"/>
+<text text-anchor="middle" x="647.65" y="-37.45" font-family="Times,serif" font-size="14.00">SERIAL_TX</text>
+</g>
+<!-- n22&#45;&gt;c39 -->
+<g id="edge26" class="edge">
+<title>n22:e&#45;&gt;c39:w</title>
+<path fill="none" stroke="#d95f02" d="M713.93,-42.5C762.81,-42.5 722.52,-132.67 756.77,-147.46"/>
+<polygon fill="#d95f02" stroke="#d95f02" points="755.9,-150.86 766.37,-149.23 757.17,-143.97 755.9,-150.86"/>
+</g>
+<!-- n23 -->
+<g id="node11" class="node">
+<title>n23</title>
+<polygon fill="none" stroke="black" points="315.8,-403.04 315.8,-417.96 277.4,-428.5 223.09,-428.5 184.69,-417.96 184.69,-403.04 223.09,-392.5 277.4,-392.5 315.8,-403.04"/>
+<text text-anchor="middle" x="250.25" y="-405.45" font-family="Times,serif" font-size="14.00">SERIAL_RX</text>
+</g>
+<!-- n23&#45;&gt;c35 -->
+<g id="edge27" class="edge">
+<title>n23:e&#45;&gt;c35:w</title>
+<path fill="none" stroke="#1b9e77" d="M317.08,-410.5C342.83,-410.5 351.76,-415.12 372.78,-416.41"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="372.59,-419.91 382.69,-416.71 372.8,-412.91 372.59,-419.91"/>
+</g>
+<!-- n24 -->
+<g id="node12" class="node">
+<title>n24</title>
+<polygon fill="none" stroke="black" points="300.29,-349.04 300.29,-363.96 270.97,-374.5 229.52,-374.5 200.2,-363.96 200.2,-349.04 229.52,-338.5 270.97,-338.5 300.29,-349.04"/>
+<text text-anchor="middle" x="250.25" y="-351.45" font-family="Times,serif" font-size="14.00">SYSCLK</text>
+</g>
+<!-- n24&#45;&gt;c35 -->
+<g id="edge28" class="edge">
+<title>n24:e&#45;&gt;c35:w</title>
+<path fill="none" stroke="#1b9e77" d="M301.76,-356.5C325.63,-356.5 333.1,-365.01 348.2,-383.5 377.02,-418.8 341.73,-478.27 372.9,-488.67"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="372.32,-492.13 382.7,-490.04 373.28,-485.19 372.32,-492.13"/>
+</g>
+<!-- n24&#45;&gt;c39 -->
+<g id="edge29" class="edge">
+<title>n24:e&#45;&gt;c39:w</title>
+<path fill="none" stroke="#1b9e77" d="M301.76,-356.5C494.05,-356.5 581.49,-429.36 731.86,-309.5 760.73,-286.48 733.96,-236.27 756.56,-225.19"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="757.22,-228.63 766.37,-223.29 755.89,-221.76 757.22,-228.63"/>
+</g>
+<!-- n24&#45;&gt;p6 -->
+<g id="edge30" class="edge">
+<title>n24:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#1b9e77" d="M301.76,-356.5C325.63,-356.5 330.28,-345.28 348.2,-329.5 376,-305.01 366.24,-265.12 393.51,-256.98"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="393.86,-260.46 403.33,-255.7 392.96,-253.52 393.86,-260.46"/>
+</g>
+<!-- v0 -->
+<g id="node13" class="node">
+<title>v0</title>
+<ellipse fill="none" stroke="black" cx="455.83" cy="-621.5" rx="27" ry="18"/>
+<text text-anchor="middle" x="455.83" y="-616.45" font-family="Times,serif" font-size="14.00">1</text>
+</g>
+<!-- c29 -->
+<g id="node15" class="node">
+<title>c29</title>
+<polygon fill="none" stroke="black" points="598.15,-584.75 598.15,-658.25 697.15,-658.25 697.15,-584.75 598.15,-584.75"/>
+<text text-anchor="middle" x="611.03" y="-640.95" font-family="Times,serif" font-size="14.00">A</text>
+<polyline fill="none" stroke="black" points="598.15,-633.75 623.9,-633.75"/>
+<text text-anchor="middle" x="611.03" y="-616.45" font-family="Times,serif" font-size="14.00">B</text>
+<polyline fill="none" stroke="black" points="598.15,-609.25 623.9,-609.25"/>
+<text text-anchor="middle" x="611.03" y="-591.95" font-family="Times,serif" font-size="14.00">S</text>
+<polyline fill="none" stroke="black" points="623.9,-584.75 623.9,-658.25"/>
+<text text-anchor="middle" x="647.65" y="-624.7" font-family="Times,serif" font-size="14.00">$6</text>
+<text text-anchor="middle" x="647.65" y="-608.2" font-family="Times,serif" font-size="14.00">$mux</text>
+<polyline fill="none" stroke="black" points="671.4,-584.75 671.4,-658.25"/>
+<text text-anchor="middle" x="684.28" y="-616.45" font-family="Times,serif" font-size="14.00">Y</text>
+</g>
+<!-- v0&#45;&gt;c29 -->
+<g id="edge36" class="edge">
+<title>v0:e&#45;&gt;c29:w</title>
+<path fill="none" stroke="#66a61e" stroke-width="3" d="M484.08,-621.5C530.31,-621.5 544.65,-621.5 585.77,-621.5"/>
+<polygon fill="#66a61e" stroke="#66a61e" stroke-width="3" points="582.61,-625 592.61,-621.5 582.61,-618 582.61,-625"/>
+</g>
+<!-- v1 -->
+<g id="node14" class="node">
+<title>v1</title>
+<ellipse fill="none" stroke="black" cx="455.83" cy="-675.5" rx="27" ry="18"/>
+<text text-anchor="middle" x="455.83" y="-670.45" font-family="Times,serif" font-size="14.00">0</text>
+</g>
+<!-- v1&#45;&gt;c29 -->
+<g id="edge37" class="edge">
+<title>v1:e&#45;&gt;c29:w</title>
+<path fill="none" stroke="#a6761d" stroke-width="3" d="M484.08,-675.5C531.96,-675.5 543.52,-650.43 585.72,-646.51"/>
+<polygon fill="#a6761d" stroke="#a6761d" stroke-width="3" points="582.78,-650.15 592.62,-646.2 582.47,-643.15 582.78,-650.15"/>
+</g>
+<!-- x7 -->
+<g id="node27" class="node">
+<title>x7</title>
+<path fill="none" stroke="#666666" d="M810.86,-603.5C810.86,-603.5 849.36,-603.5 849.36,-603.5 855.36,-603.5 861.36,-609.5 861.36,-615.5 861.36,-615.5 861.36,-627.5 861.36,-627.5 861.36,-633.5 855.36,-639.5 849.36,-639.5 849.36,-639.5 810.86,-639.5 810.86,-639.5 804.86,-639.5 798.86,-633.5 798.86,-627.5 798.86,-627.5 798.86,-615.5 798.86,-615.5 798.86,-609.5 804.86,-603.5 810.86,-603.5"/>
+<text text-anchor="middle" x="830.11" y="-616.7" font-family="Times,serif" font-size="14.00" fill="#666666">0:0 &#45; 0:0</text>
+</g>
+<!-- c29&#45;&gt;x7 -->
+<g id="edge31" class="edge">
+<title>c29:e&#45;&gt;x7:w</title>
+<path fill="none" stroke="#a6761d" stroke-width="3" d="M698.15,-621.5C738.49,-621.5 751.29,-621.71 786.67,-621.74"/>
+<polygon fill="#a6761d" stroke="#a6761d" stroke-width="3" points="783.31,-625.24 793.32,-621.75 783.32,-618.24 783.31,-625.24"/>
+</g>
+<!-- c30&#45;&gt;c29 -->
+<g id="edge32" class="edge">
+<title>c30:e&#45;&gt;c29:w</title>
+<path fill="none" stroke="#7570b3" d="M500.33,-560.75C542.15,-560.75 549.99,-590.78 585.7,-596.17"/>
+<polygon fill="#7570b3" stroke="#7570b3" points="585.42,-599.66 595.64,-596.89 585.92,-592.68 585.42,-599.66"/>
+</g>
+<!-- c40&#45;&gt;p6 -->
+<g id="edge33" class="edge">
+<title>c40:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#a6761d" d="M313.87,-141.75C374.43,-141.75 344.63,-241.31 393.54,-254.14"/>
+<polygon fill="#a6761d" stroke="#a6761d" points="392.98,-257.6 403.32,-255.32 393.81,-250.65 392.98,-257.6"/>
+</g>
+<!-- c41&#45;&gt;p6 -->
+<g id="edge34" class="edge">
+<title>c41:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#e6ab02" d="M313.87,-201.75C356.79,-201.75 358.01,-246.66 393.76,-254.38"/>
+<polygon fill="#e6ab02" stroke="#e6ab02" points="393.02,-257.82 403.32,-255.35 393.73,-250.86 393.02,-257.82"/>
+</g>
+<!-- c42&#45;&gt;p6 -->
+<g id="edge35" class="edge">
+<title>c42:e&#45;&gt;p6:w</title>
+<path fill="none" stroke="#1b9e77" d="M313.87,-299.75C354.79,-299.75 359.33,-263.09 393.71,-256.51"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" points="393.68,-260.02 403.32,-255.64 393.04,-253.05 393.68,-260.02"/>
+</g>
+<!-- p2 -->
+<g id="node22" class="node">
+<title>p2</title>
+<path fill="none" stroke="black" d="M500.58,-335C500.58,-335 411.08,-335 411.08,-335 405.08,-335 399.08,-329 399.08,-323 399.08,-323 399.08,-306 399.08,-306 399.08,-300 405.08,-294 411.08,-294 411.08,-294 500.58,-294 500.58,-294 506.58,-294 512.58,-300 512.58,-306 512.58,-306 512.58,-323 512.58,-323 512.58,-329 506.58,-335 500.58,-335"/>
+<text text-anchor="middle" x="455.83" y="-317.7" font-family="Times,serif" font-size="14.00">PROC $10</text>
+<text text-anchor="middle" x="455.83" y="-301.2" font-family="Times,serif" font-size="14.00">top.v:28.15&#45;28.35</text>
+</g>
+<!-- p2&#45;&gt;n15 -->
+<g id="edge7" class="edge">
+<title>p2:e&#45;&gt;n15:w</title>
+<path fill="none" stroke="#7570b3" stroke-width="3" d="M513.58,-314.5C553.03,-314.5 561.25,-288.22 594.84,-283.29"/>
+<polygon fill="#7570b3" stroke="#7570b3" stroke-width="3" points="591.88,-287.01 601.61,-282.82 591.39,-280.02 591.88,-287.01"/>
+</g>
+<!-- p3 -->
+<g id="node23" class="node">
+<title>p3</title>
+<path fill="none" stroke="black" d="M102.9,-577C102.9,-577 13.4,-577 13.4,-577 7.4,-577 1.4,-571 1.4,-565 1.4,-565 1.4,-548 1.4,-548 1.4,-542 7.4,-536 13.4,-536 13.4,-536 102.9,-536 102.9,-536 108.9,-536 114.9,-542 114.9,-548 114.9,-548 114.9,-565 114.9,-565 114.9,-571 108.9,-577 102.9,-577"/>
+<text text-anchor="middle" x="58.15" y="-559.7" font-family="Times,serif" font-size="14.00">PROC $9</text>
+<text text-anchor="middle" x="58.15" y="-543.2" font-family="Times,serif" font-size="14.00">top.v:19.15&#45;19.31</text>
+</g>
+<!-- p3&#45;&gt;n16 -->
+<g id="edge10" class="edge">
+<title>p3:e&#45;&gt;n16:w</title>
+<path fill="none" stroke="#d95f02" stroke-width="3" d="M115.9,-556.5C146.16,-556.5 156.47,-556.5 181.9,-556.5"/>
+<polygon fill="#d95f02" stroke="#d95f02" stroke-width="3" points="178.82,-560 188.82,-556.5 178.82,-553 178.82,-560"/>
+</g>
+<!-- p4 -->
+<g id="node24" class="node">
+<title>p4</title>
+<path fill="none" stroke="black" d="M500.58,-217C500.58,-217 411.08,-217 411.08,-217 405.08,-217 399.08,-211 399.08,-205 399.08,-205 399.08,-188 399.08,-188 399.08,-182 405.08,-176 411.08,-176 411.08,-176 500.58,-176 500.58,-176 506.58,-176 512.58,-182 512.58,-188 512.58,-188 512.58,-205 512.58,-205 512.58,-211 506.58,-217 500.58,-217"/>
+<text text-anchor="middle" x="455.83" y="-199.7" font-family="Times,serif" font-size="14.00">PROC $8</text>
+<text text-anchor="middle" x="455.83" y="-183.2" font-family="Times,serif" font-size="14.00">top.v:15.15&#45;15.34</text>
+</g>
+<!-- p4&#45;&gt;n18 -->
+<g id="edge15" class="edge">
+<title>p4:e&#45;&gt;n18:w</title>
+<path fill="none" stroke="#1b9e77" stroke-width="3" d="M513.58,-196.5C535.59,-196.5 537.25,-218.86 552.58,-226.2"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" stroke-width="3" points="548.5,-228.91 559.01,-227.56 549.95,-222.06 548.5,-228.91"/>
+</g>
+<!-- p5 -->
+<g id="node25" class="node">
+<title>p5</title>
+<path fill="none" stroke="black" d="M497.2,-158C497.2,-158 414.45,-158 414.45,-158 408.45,-158 402.45,-152 402.45,-146 402.45,-146 402.45,-129 402.45,-129 402.45,-123 408.45,-117 414.45,-117 414.45,-117 497.2,-117 497.2,-117 503.2,-117 509.2,-123 509.2,-129 509.2,-129 509.2,-146 509.2,-146 509.2,-152 503.2,-158 497.2,-158"/>
+<text text-anchor="middle" x="455.83" y="-140.7" font-family="Times,serif" font-size="14.00">PROC $7</text>
+<text text-anchor="middle" x="455.83" y="-124.2" font-family="Times,serif" font-size="14.00">top.v:13.9&#45;13.24</text>
+</g>
+<!-- p5&#45;&gt;n19 -->
+<g id="edge19" class="edge">
+<title>p5:e&#45;&gt;n19:w</title>
+<path fill="none" stroke="#e6ab02" d="M510.2,-137.5C545.45,-137.5 550.58,-167.11 579.47,-173.35"/>
+<polygon fill="#e6ab02" stroke="#e6ab02" points="578.96,-176.82 589.26,-174.35 579.67,-169.85 578.96,-176.82"/>
+</g>
+<!-- p6&#45;&gt;n15 -->
+<g id="edge8" class="edge">
+<title>p6:e&#45;&gt;n15:w</title>
+<path fill="none" stroke="#7570b3" stroke-width="3" d="M506.83,-255.5C548.46,-255.5 558.69,-277.87 594.68,-281.89"/>
+<polygon fill="#7570b3" stroke="#7570b3" stroke-width="3" points="591.44,-285.22 601.61,-282.26 591.81,-278.23 591.44,-285.22"/>
+</g>
+<!-- p6&#45;&gt;n18 -->
+<g id="edge16" class="edge">
+<title>p6:e&#45;&gt;n18:w</title>
+<path fill="none" stroke="#1b9e77" stroke-width="3" d="M506.83,-255.5C530.35,-255.5 534.64,-236.28 552.16,-230.27"/>
+<polygon fill="#1b9e77" stroke="#1b9e77" stroke-width="3" points="549.63,-234.21 558.97,-229.2 548.54,-227.3 549.63,-234.21"/>
+</g>
+<!-- p6&#45;&gt;n19 -->
+<g id="edge20" class="edge">
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+<title>x7:e&#45;&gt;n21:w</title>
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+</g>
+<!-- x8&#45;&gt;n20 -->
+<g id="edge23" class="edge">
+<title>x8:e&#45;&gt;n20:w</title>
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diff --git a/atk16_fpga/top.v b/atk16_fpga/top.v
index c67ade2..6fcbddd 100644
--- a/atk16_fpga/top.v
+++ b/atk16_fpga/top.v
@@ -9,28 +9,37 @@ module top (
     output LED2
 );
 
-    // One-cycle pulse to trigger transmission.
-    reg start_tx = 1'b0;
-    // Data byte to be transmitted.
-    reg [7:0] data_to_send = 8'b0;
-    // Busy flag from the transmitter.
-    wire tx_busy;
+    // State machine states.
+    localparam RX_START = 0;
+    localparam WAIT_RX_DONE = 1;
+    localparam START_TX = 2;
+    localparam TX_IN_PROG = 3;
+    localparam WAIT_TX_DONE = 4;
+    localparam HANDLE_RX_DATA = 5;
+    localparam SEND_STRING_WELCOME = 6;
+    localparam SEND_STRING_HELP = 7;
+    localparam SEND_STRING_PROGRAM_READY = 8;
+    localparam RECEIVE_PROGRAM_DATA = 9;
 
-    reg [7:0] letter_a = 8'd97;
+    reg [7:0] state = SEND_STRING_WELCOME;
 
-    // State machine states.
-    localparam WAIT_RX_BUSY = 3'd0;
-    localparam WAIT_RX_DONE = 3'd1;
-    localparam START_TX_1 = 3'd2;
-    localparam START_TX_2 = 3'd3;
-    localparam WAIT_TX_DONE = 3'd4;
+    // SEND_WELCOME data
+    `STR_welcome
+    reg [7:0] welcome_index = 0;
+
+    // SEND_STRING_HELP data
+    `STR_help
+    reg [7:0] help_index = 0;
 
-    reg [2:0] state = WAIT_RX_BUSY;
+    // SEND_STRING_PROGRAM_READY data
+    `STR_program_ready
+    reg [7:0] program_ready_index = 0;
 
     // Synchronous state machine with reset.
     always @(posedge SYSCLK) begin
         case (state)
-            WAIT_RX_BUSY: begin
+            // STATES FOR RX
+            RX_START: begin
                 if (!rx_done) begin
                     state <= WAIT_RX_DONE;
                 end
@@ -38,21 +47,20 @@ module top (
 
             WAIT_RX_DONE: begin
                 if (rx_done) begin
-                    state <= START_TX_1;
+                    state <= state_after_rx;
                 end
             end
 
-            START_TX_1: begin
+            // STATES FOR TX
+            START_TX: begin
                 if (!tx_busy) begin
-                    //data_to_send <= letter_a;
-                    data_to_send <= data_to_receive;
                     start_tx <= 1'b1;  // trigger transmission
-                    state <= START_TX_2;
+                    state <= TX_IN_PROG;
                 end
             end
 
             // After issuing the start pulse, wait for tx_busy to go high.
-            START_TX_2: begin
+            TX_IN_PROG: begin
                 start_tx <= 1'b0;  // ensure pulse is only one cycle.
                 state <= WAIT_TX_DONE;
             end
@@ -60,35 +68,104 @@ module top (
             // Wait for the transmitter to finish sending the byte.
             WAIT_TX_DONE: begin
                 if (!tx_busy) begin
-                    state <= WAIT_RX_BUSY;
+                    state <= state_after_tx;
                 end
             end
 
-            default: state <= WAIT_RX_BUSY;
+            // STATES FOR PROCESSING DATA
+            HANDLE_RX_DATA: begin
+                if (data_rx == cmd_program) begin
+                    state <= SEND_STRING_PROGRAM_READY;
+                end else if (data_rx == cmd_help) begin
+                    state <= SEND_STRING_HELP;
+                end else begin
+                    state <= RX_START;
+                end
+            end
+
+            SEND_STRING_WELCOME: begin
+                if (welcome_index < 8'd`LEN_welcome) begin
+                    data_tx <= str_welcome[welcome_index];
+                    welcome_index <= welcome_index + 1;
+                    state <= START_TX;
+                    state_after_tx <= SEND_STRING_WELCOME;
+                end else begin
+                    welcome_index <= 0;
+                    state <= RX_START;
+                    state_after_tx <= RX_START;
+                end
+            end
+
+            SEND_STRING_HELP: begin
+                if (help_index < 8'd`LEN_help) begin
+                    data_tx <= str_help[help_index];
+                    help_index <= help_index + 1;
+                    state <= START_TX;
+                    state_after_tx <= SEND_STRING_HELP;
+                end else begin
+                    help_index <= 0;
+                    state <= RX_START;
+                    state_after_tx <= RX_START;
+                end
+            end
+
+            SEND_STRING_PROGRAM_READY: begin
+                if (program_ready_index < 8'd`LEN_program_ready) begin
+                    data_tx <= str_program_ready[program_ready_index];
+                    program_ready_index <= program_ready_index + 1;
+                    state <= START_TX;
+                    state_after_tx <= SEND_STRING_PROGRAM_READY;
+                end else begin
+                    program_ready_index <= 0;
+                    state <= RECEIVE_PROGRAM_DATA;
+                    state_after_tx <= RX_START;
+                end
+            end
+
+            RECEIVE_PROGRAM_DATA: begin
+                // TODO write data to flash
+                state <= RX_START;
+                state_after_rx <= RECEIVE_PROGRAM_DATA;
+            end
+
+            default: state <= RX_START;
         endcase
 
     end
 
+    // One-cycle pulse to trigger transmission.
+    reg        start_tx = 1'b0;
+    // Data byte to be transmitted.
+    reg  [7:0] data_tx = 8'b0;
+    // Busy flag from the transmitter.
+    wire       tx_busy;
+    // State to transition to after TX done.
+    reg  [7:0] state_after_tx = RX_START;
+
+    reg  [7:0] cmd_help = 8'd104;  // h
+    reg  [7:0] cmd_program = 8'd112;  // p
+
     // Instantiate the UART transmitter.
     uart_tx uart_inst (
         .clk  (SYSCLK),
         .start(start_tx),   // One-cycle pulse to start transmission.
-        .data (data_to_send),
+        .data (data_tx),
         .tx   (SERIAL_TX),
         .busy (tx_busy)
     );
 
-    wire [7:0] data_to_receive;
+    wire [7:0] data_rx;
     wire rx_done;
+    reg [7:0] state_after_rx = HANDLE_RX_DATA;
 
     uart_rx uart_rx_inst (
         .clk (SYSCLK),
         .rx  (SERIAL_RX),
-        .data(data_to_receive),
+        .data(data_rx),
         .done(rx_done)
     );
 
-    assign LED1 = data_to_receive == letter_a ? 1 : 0;
+    assign LED1 = data_rx == cmd_program;
     assign LED2 = LED1;
 
 endmodule