update readme

Author: ArcaneNibble

README.md

@@ -1,10 +1,20 @@
 # PY32 fidget spinner demo
 
-Over-engineered with a MEMS accelerometer (why else would you bother with a 32-bit MCU?)
+![3d render of board](revA-render.png)
 
-## Main parts
+This is a quick-and-dirty demo of _just_ how cheap embedded compute can get nowadays — approximately USD$6 for an *assembled* board with a 32-bit Cortex-M0.
+
+In order to actually make good use of this available compute, the idea was to build a modern (i.e. state-space) control theory estimator to determine the orientation of the fidget spinner from accelerometer data, rather than more traditional approaches involving hall effect sensors.
+
+## Status
+
+Revision A was ordered from JLCPCB, and all of the essential components work.
+
+The state estimator has yet to be written, as the author is aphantasic and not much of a shape rotator (and thus struggling with writing out the necessary "physical world" equations).
+
+## Main components
 
 * PY32F002AL15 (MCU)
 * SC7A20 (accelerometer)
-* CR2032 batteries
-* Charlieplexed LEDs
+* CR2032 battery
+* 30 charlieplexed LEDs