Merge branch 'main' of github.com:fruit-bat/pico-zxspectrum into main

Author: burt

README.md

@@ -13,6 +13,87 @@ Uses [Wren's Amazing PicoDVI](https://github.com/Wren6991/PicoDVI) library.
 ## First light
 <img src="docs/zxspectrum_screen_1.jpg" width="400"/>
 
+## Prototype
+<img src="docs/pico_sorcerer_prototype_1.jpg" width="400"/>
+
+## Wiring
+
+|       | SPI0  | GPIO  | Pin   | SPI       | MicroSD 0 | HDMI/DVI  |      Description       | 
+| ----- | ----  | ----- | ---   | --------  | --------- | --------- | ---------------------- |
+| MISO  | RX    | 4     | 6     | DO        | DO        |           | Master In, Slave Out   |
+| CS0   | CSn   | 5     | 7     | SS or CS  | CS        |           | Slave (or Chip) Select |
+| SCK   | SCK   | 2     | 4     | SCLK      | CLK       |           | SPI clock              |
+| MOSI  | TX    | 3     | 5     | DI        | DI        |           | Master Out, Slave In   |
+| CD    |       | 22    | 29    |           | CD        |           | Card Detect            |
+| GND   |       |       | 3     |           | GND       |           | Ground                 |
+| 3v3   |       |       | 36    |           | 3v3       |           | 3.3 volt power         |
+| GND   |       |       | 18,23 |           |           | GND       | Ground                 |
+| GP16  |       | 16    | 21    |           |           | TX2+      | Data channel 2+        |
+| GP17  |       | 17    | 22    |           |           | TX2-      | Data channel 2-        |
+| GP18  |       | 18    | 24    |           |           | TX1+      | Data channel 1+        |
+| GP19  |       | 19    | 25    |           |           | TX1-      | Data channel 1-        |
+| GP12  |       | 12    | 16    |           |           | TX0+      | Data channel 0+        |
+| GP13  |       | 13    | 17    |           |           | TX0-      | Data channel 0-        |
+| GP14  |       | 14    | 19    |           |           | TXC+      | Clock +                |
+| GP15  |       | 15    | 20    |           |           | TXC-      | Clock -                |
+
+![image](https://www.raspberrypi.org/documentation/microcontrollers/images/Pico-R3-SDK11-Pinout.svg "Pinout")
+
+## Components 
+<a href="https://shop.pimoroni.com/products/raspberry-pi-pico">
+<img src="https://cdn.shopify.com/s/files/1/0174/1800/products/P1043509-smol_1024x1024.jpg" width="200"/>
+</a>
+
+<a href="https://buyzero.de/products/raspberry-pi-pico-dvi-sock-videoausgabe-fur-den-pico">
+<img src="https://cdn.shopify.com/s/files/1/1560/1473/products/Raspberry-Pi-Pico-Video-Output-DVI-Sock-topview_1200x.jpg" width="200"/>
+</a>
+
+<a href="https://thepihut.com/products/adafruit-dvi-breakout-board-for-hdmi-source-devices">
+<img src="https://cdn.shopify.com/s/files/1/0176/3274/products/67e1a982-7668-48e2-acaf-df9de6f6e6fe_600x.jpg" width="200"/>
+</a>
+
+<a href="https://thepihut.com/products/adafruit-micro-sd-spi-or-sdio-card-breakout-board-3v-only">
+<img src="https://cdn.shopify.com/s/files/1/0176/3274/products/4682-01_dcdcf68d-19aa-4deb-b758-471e8e7baf62_600x.jpg" width="200"/>
+</a>
+                                                                                                        
+## Issues
+USB host mode required for keyboard input still seems to need a [patch to the Pico SDK](https://github.com/raspberrypi/tinyusb/pull/7/files) version of TinyUSB. The patch seems to work very reliably unless the keyboard is removed and reconnected, which causes the Pico to 'panic'.
+
+## Build
+Fistly patch up the TinyUSB library for USB host mode, as described [here](https://github.com/raspberrypi/tinyusb/pull/7/files).
+
+This code needs to be cloned into the 'apps' folder of the [PicoDVI](https://github.com/Wren6991/PicoDVI) library. 
+```
+cd PicoDVI/software/apps
+git@github.com:fruit-bat/pico-zxspectrum.git zxspectrum
+```
+
+In the 'apps' folder add the following line to CMakeLists.txt
+```
+add_subdirectory(zxspectrum)
+```
+In the build folder:
+```
+cmake
+make -j4 ZxSpectrum
+cp apps/zxspectrum/ZxSpectrum.uf2 /media/pi/RPI-RP2/
+```
+
+## Special keys
+
+| Key | Action |
+| --- | ------ |
+| F4 | Toggle Z80 4Mhz moderator |
+| F11 + F12 | Reset |
+
+## Missing features
+* Write 'tape' format
+* Read/Write WAV files
+* Audio input
+* Audio Output
+* Centronics interface
+* Serial interface (Uart 0 is currently used for debug) 
+
 # References
 [Wren's Amazing PicoDVI](https://github.com/Wren6991/PicoDVI)<br/>
 http://www.breakintoprogram.co.uk/computers/zx-spectrum/screen-memory-layout<br/>