README.md: minor changes

README.md

@@ -6,9 +6,44 @@ Code was rushed in a couple of days.
 
 Sorry.
 
+
+## Hardware Specifications
+- CH32V003F4P6 MCU
+- IS31FL3729 matrix LED controller
+- 9x RGB LED, one for each character
+- White, amber and green LEDs for the cursor
+- Adjustment knob to feel like the old times
+- 8Kbit EEPROM for storing user configurations
+
+
 ## Manual
 
-User instructions can be found at trueControl BASIC:
+User instructions for the addon can be found at trueControl BASIC:
 * https://basic.truecontrol.org/database/dc32/retro-tech-gat/
 
-Firmware is a MounRiver Studio project. You can freely download MounRiver Studio at http://mounriver.com/download 
+
+## Building
+
+Firmware is a MounRiver Studio project. You can freely download MounRiver Studio at http://mounriver.com/download
+
+
+## Flashing
+
+Firmware can be debugged and flashed from within MounRiver Studio using a WCH-LinkE debug probe.
+
+Alternatively, a UART bootloader is available. A Windows flashing utility is provided. The bootloader uses WCHISP protocol, so any WCHISP flash utility supporting CH32V003 should work (untested).
+
+Connect any standard TTL UART into the GAT header in the rear, power with 3V3, then use the flashing utility to load new firmware.
+
+To activate the bootloader, hold down BTN2 while powering on. LED4 (orange) will rapidly flash to indicate the addon is in bootloader mode.
+
+
+```
+RX and TX indicated are from
+the point of view of the host
+
+     /----|  |----\
+     | TX  nc 3V3 |
+     | RX  nc GND |
+     \------------/
+```