diff --git a/doc/todo.md b/doc/todo.md
new file mode 100644
index 0000000..f39c55f
--- /dev/null
+++ b/doc/todo.md
@@ -0,0 +1,27 @@
+Copyright 2023 (C) Peter McGoron.
+
+This file is a part of Upsilon, a free and open source software project.
+For license terms, refer to the files in `doc/copying` in the Upsilon 
+source distribution.
+
+__________________________________________________________________________
+
+* The control loop is inflexible and poorly documented.
+* Waveform modules might be necessary but are untested.
+
+# Coptic: Upsilon 2.0
+
+Coptic is an improved architecture for Upsilon.
+
+Coptic would have multiple RV32EM CPUs (configurable at build time) that
+run independently of the main Linux CPU. Along with the main RAM segment
+the Linux CPU can access block RAM segments which run independently of
+system RAM.
+
+The Linux CPU can
+
+* Allocate main RAM segments to a CPU for rw access
+* Allocate entire BRAM blocks to a CPU
+* Receive interrupts from CPUs
+* Send interrupts to CPUs
+* Start CPUs, halt CPUs, reset CPUs
diff --git a/gateware/Makefile b/gateware/Makefile
index faedd63..1c3f32a 100644
--- a/gateware/Makefile
+++ b/gateware/Makefile
@@ -8,7 +8,7 @@
 
 DEVICETREE_GEN_DIR=.
 
-all: rtl_codegen build/digilent_arty/digilent_arty.bit arty.dtb pin_io.c
+all: rtl_codegen build/digilent_arty/digilent_arty.bit arty.dtb mmio.py
 
 rtl_codegen:
 	cd rtl && make