update README for new ground station

Author: rhettg

README.md

@@ -29,6 +29,16 @@ technology for an open-source Mars rover.
 
 ## Components
 
+### CiC
+
+[`README.md`](libraries/CiC)
+
+The flight control system framework that powers both the Rover and Ground is a
+bespoke C library providing capabilities that I deem necessary. Much of my focus
+has been on telemetry and debuggability of an increasingly sophisticated
+software stack. I mean, on Mars who is going plug into the Serial port and hit
+the reset button for you?
+
 ### Rover
 
 [`rover.ino`](rover/rover.ino)
@@ -51,23 +61,66 @@ The plan is to find the shortcomings from this simple setup and iterate.
 
 ### Ground
 
-[`ground.ino`](ground/ground.ino)
+To communicate with the Rover, a ground station is needed. This is built around:
 
-The ground station is essentially a slimmed down version of the Rover, meant to
-be teathered to a computer via Serial port.
+* Raspberry Pi 4
+* RFM69 Transceiver (identical to the Rover's)
 
-* Arduino Duo
-* RFM69 Transceiver
+The software stack is built around several sub-components organized as Unixy as
+possible. These components ideally handle a single task and are easily
+replacable as mission demands evolve.
 
-### CiC
+#### rfm69
 
-[`README.md`](libraries/CiC)
+[`rfm69`](rfm69/bin/rfm69)
 
-The flight control system framework that powers both the Rover and Ground is a
-bespoke C library providing capabilities that I deem necessary. Much of my focus
-has been on telemetry and debuggability of an increasingly sophisticated
-software stack. I mean, on Mars who is going plug into the Serial port and hit
-the reset button for you?
+This python script uses CircuitPython to interface with the rfm69 transceiver
+hardware. It presents a unix domain socket on the system `/var/stubborn/radio`
+which other processes can use to send and receive data over the radio. 
+
+Bytes written to the socket are sent directly over the radio (and hopefully
+received by the Rover).
+
+Bytes recieved are sent to to the listening client.
+
+Only a single client can connect at a time.
+
+#### comsock
+
+This C program is built on the same CiC stack as the rover and provides a
+high-level communication interface to the Rover.
+
+Client connect to comsock over a unix domain socket (`/var/stubborn/comsock`)
+and send commands to the rover such as:
+
+    FWD 255
+
+The server will send this command to the Rover and display the result:
+
+    OK
+
+Or in the event of an error:
+
+    ERR 3
+
+The comsock service also receives telemetry data from the Rover. It's writen in
+two formats.
+
+`/var/stubborn/to` is a tab-delimited data file in the format:
+
+    NOW=2403777634	UP=167495	LOOP=0	COM=1	RSSI=229	ERR=2
+
+`/var/stubborn/to.json` is JSON formatted:
+
+    {"NOW": 1632030343, "UP": 19252, "LOOP": 0, "RSSI": 229, "COM": 2}
+
+#### Ground Data System (gds)
+
+The Ground Data System is a user interface for the ground station that uses the
+underlying components to receive commands from the user and display telemetry
+about the Rover's operation.
+
+It's written in Go in uses the `tview` library to present a fun terminal-based UI.
 
 ## Usage
 
@@ -81,5 +134,13 @@ Rather than rely on the Arduino IDE, scripts powered by `arduino-cli` are availa
 
 * [`rover/script/build`](rover/script/build)
 * [`rover/script/upload`](rover/script/upload)
-* [`ground/script/build`](ground/script/build)
-* [`ground/script/upload`](ground/script/upload)
+
+### Ground Infrastructure
+
+Ground station services are managed using systemd. Unit files are for radio and comsock services.
+
+gds can be run directly using `go`:
+
+    go run main.go
+
+This may change as this component increases in complexity.