Updated README

Updated MCU list, added PCB descriptions, more usage information, cleanup

README.MD

@@ -2,8 +2,8 @@
 
 ## What is this?
 
-**LowresDisplayTester** is the firmware for AVR MCUs that enables creation of low-part-count and low-cost video generator (sync generator/black burst generator/genlock) device.
-It also can be used as a rudimentary pattern generator, but not very stable one. Pattern generation can be disabled via a jumper on the PCB.
+**LowresDisplayTester** is a small device with AVR MCUs that enables creation of low-part-count and low-cost video generator (sync generator/black burst generator/genlock) device.
+It also can be used as a rudimentary pattern generator, but not very stable one. Pattern generation can be disabled via a jumper on the PCB. This device also performs tests on character displays.
 
 ## Features
 
@@ -17,10 +17,10 @@ It also can be used as a rudimentary pattern generator, but not very stable one.
 
 ## Video outputs
 
-- 525i/29.97 composite (NTSC no color, black level fill + white vertical bars)
-- 625i/25 composite (PAL/SECAM no color, black level fill + white vertical bars)
-- 640x480 60Hz VGA (blue fill + orange vertical bars)
-- 640x200 60Hz CGA/EGA (blue fill + cyan/magenta vertical bars)
+- Composite RCA 525i/29.97 (NTSC no color, black level fill + white vertical bars)
+- Composite RCA 625i/25 (PAL/SECAM no color, black level fill + white vertical bars)
+- VGA 640x480 60Hz (blue fill + orange vertical bars)
+- CGA/EGA 640x200 60Hz (blue fill + cyan/magenta vertical bars)
 
 Only one video standard can be selected at any time.
 
@@ -29,11 +29,11 @@ Only one video standard can be selected at any time.
 
 ## Firmware
 
-Adapter utilizes **Atmel AVR** MCU for all timing, video generation and data protocols. Firmware project is done in **AtmelStudio 7**.
+Device utilizes **Atmel AVR** MCU for all timing, video generation and data protocols. Firmware project is done in **AtmelStudio 7**.
 
-Target MCU is **ATmega 168** (either variant). But firmware should be compilable and working on **ATmega 328** variants as well. **ATmega 48** and **ATmega 88** are not supported due to low ROM capacity.
+Target MCU is **ATmega 168** (either variant). But firmware should be compilable and working on **ATmega 328** variants as well. **ATmega 48** and **ATmega 88** are not supported due to low ROM capacity. **ATmega 16** and **ATmega 32** are also supported (but require a different PCB).
 
-MCU must be clocked from external 16.0 MHz Xtal for precise timing.
+MCU must be clocked from external **16.0 MHz Xtal** for precise timing.
 
 Due to high clock and dependance of output analog levels on logic levels MCU should be run on voltages from **4.1 V** to **5.0 V**. Thus BOD (Brown-out Detector) is enabled by MCU fuses.
 
@@ -54,7 +54,7 @@ In hex form:
 </details>
 
 <details>
-<summary>AVR fuses for ATmega88/ATmega168</summary>
+<summary>AVR fuses for ATmega168</summary>
 
 - **SUT1** = 0
 - **CKSEL3** = 0
@@ -70,7 +70,7 @@ In hex form:
 </details>
 
 <details>
-<summary>AVR fuses for ATmega8/ATmega16/ATmega32</summary>
+<summary>AVR fuses for ATmega16/ATmega32</summary>
 
 - **BODLEVEL** = 0
 - **BODEN** = 0
@@ -86,15 +86,23 @@ In hex form:
 
 ## Hardware
 
-Sorry, no electrical schematics at the moment...
+Sorry, no electrical schematics at the moment.
+
+Adapter fits onto single PCB. PCB project is done in **Sprint Layout 6**.
+Sizes of the boards:
+- **LRDT.328SMD.xx** (88x41 mm) for ATmega168/ATmega328 in TQFP package
+- **LRDT.328DIP.xx** (78x53 mm) for ATmega168/ATmega328 in DIP package
+- **LRDT.32DIP.xx** (78x62 mm) for ATmega16/ATmega32 in DIP package
+
+"*xx*" at the end denotes revision of each PCB.
 
 <details>
-<summary>Pinout for ATmega 88/168/328 MCU in SMD packages</summary>
+<summary>Pinout for ATmega 168/328 MCU in SMD packages</summary>
 
 Power supply:
 - **pin 4** *(VCC)*: +5 V supply
 - **pin 6** *(VCC)*: +5 V supply
-- **pin 18** *(AVCC)*: +5 V supply
+- **pin 18** *(AVCC)*: +5 V supply (BOD)
 - **pin 20** *(AREF)*: +5 V reference
 - **pin 3** *(GND)*: 0 V (common)
 - **pin 5** *(GND)*: 0 V (common)
@@ -136,11 +144,11 @@ UART displays serial port:
 </details>
 
 <details>
-<summary>Pinout for ATmega 88/168/328 MCU in DIP packages</summary>
+<summary>Pinout for ATmega 168/328 MCU in DIP packages</summary>
 
 Power supply:
 - **pin 7** *(VCC)*: +5 V supply
-- **pin 20** *(AVCC)*: +5 V supply
+- **pin 20** *(AVCC)*: +5 V supply (BOD)
 - **pin 21** *(AREF)*: +5 V reference
 - **pin 8** *(GND)*: 0 V (common)
 - **pin 22** *(GND)*: 0 V (common)
@@ -185,7 +193,7 @@ UART displays serial port:
 
 Power supply:
 - **pin 10** *(VCC)*: +5 V supply
-- **pin 30** *(AVCC)*: +5 V supply
+- **pin 30** *(AVCC)*: +5 V supply (BOD)
 - **pin 32** *(AREF)*: +5 V reference
 - **pin 11** *(GND)*: 0 V (common)
 - **pin 31** *(GND)*: 0 V (common)
@@ -227,25 +235,27 @@ UART displays serial port:
 
 ## Usage
 
+Power supply connects to the default (center-positive) DC barrel jack on the PCB. The board is equiped with reverse-polarity protection. Supplied voltage should in range of **8...20 Volts**. Onboard linear volate regulator provides 5V for MCU and connected character display.
+
+On power-on MCU starts generating video signal for selected video standard. In parallel MCUs tries to communicate with character display through *HD44780* connector.
+
 > [!NOTE]
 > Only one of the display output connectors should be used at any time.
 
-## Demo
-
+Video standard is selected through "MODE" switches.
 
 ## Current state
 - Two-switch video selector works
 - PAL and NTSC frame generation works ok
 - VGA, EGA and CGA frame generation works ok
 - Bar pattern for PAL/NTSC/CGA/EGA/VGA has horizontal jitter due to AVR interrupt jitter
-- HD44780 driver works fine
+- HD44780 parallel (4-bit) driver works fine
 
 ## Plans
 - Update I2C driver to working state
 - Write driver for character displays with I2C bus
 - Write driver for UART Futaba character displays
 - Write driver for UART terminal (?)
-- Maybe add support for graphical displays
 
 ## License
 Program copyright 2022-2024.