Added README

README.md

@@ -0,0 +1,68 @@
+# Updated Sonar System
+
+## Design Goals
+
+- 4x 20MSPS channels @ > 8 bits
+- Ethernet data channel
+- Simplified software stack (or at least fewer layers of components)
+- Well-documented
+
+## System Architecture
+
+<!-- made with asciiflow.com -->
+```
+┌─────────────┐
+│Main Computer│
+└─────▲───────┘
+      │
+      │
+      │
+┌─────┴──────┐
+│Ethernet PHY│
+│      ▲     │           Interface Board (x4)
+│      │     │       ┌──────────────────────────────┐
+│      │     │       │                              │            ┌─────────────┐
+│      │     │◄──────┤ LVDS Serializer◄─────────ADC │◄───────────┤ Hydrophones │
+│      │     │       │                              │            └─────────────┘
+│      │     │       └──────────────────────────────┘
+│    FPGA    │
+└─────▲──────┘
+      │ Dev Board
+      │ or
+      │ Custom Board
+      │
+      │
+      │
+   ┌──┴───────────────────┐
+   │ Peak Detector Board  │
+   └──────────────────────┘
+               (Temporary)
+```
+
+## RTL Architecture
+
+#### Diagram TODO
+
+The plan is to use LiteX and let it do most of the heavy lifting. Components to
+generate:
+
+- Softcore (microwatt probably, I'm feeling a bit hipster)
+- Main memory bus
+- DMA engine
+- Gigabit Ethernet MAC
+
+THis way the only actual RTL to write is the peripheral that interacts with the ADCs,
+which should be very simple. To do early bringup I can start with a blinky peripheral to
+demonstrate access to the bus, and then I can keep adding functionality.
+
+## Software Planning
+
+I should be able to target the microwatt with Rust, hopefully do some embassy work and
+then that gives me a good dev environment.
+
+Should make sure to have a debug port available as early as possible.
+
+I will make the interface as generic as possible, so it should be easy to swap out, but I
+will start by targetting zmq so I can change as little of the software stack as possible.
+
+[Reference for custom target triple](https://docs.rust-embedded.org/embedonomicon/custom-target.html)