pico-zxspectrum
48k/128k ZX Spectrum for Raspberry Pico Pi RP2040
This is a basic 48k/128k ZX Spectrum emulation on the RP2040 with DVI output.
Uses Wren's Amazing PicoDVI and CarlK's Super no OS FAT FS for Pico libraries.
Features
- DVI over HDMI output
- USB Keyboard & Joysticks
- PWM sound for ear, mic and AY-3-8912
- 12 quick save slots
- Load from .z80 snapshot files
- Read from .tap tape files
- On screen menu system (work in progress)
- Kempston and Sinclair joystick emulation
Screen shots
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 - | |||
| GP20 | 20 | 26 | PWM audio out |
Prototype
Audio filter
It's a good idea to filter out high frequencies from the PWM audio output. The following components were chosen as I found them in a draw... but it sounds ok.
Components
Issues
The Z80 is interrupted at the end of each frame at 60hz. The original Spectrum wrote frames at 50hz, so some code runs more frequently than it used to; there is a 4Mhz CPU setting that kind of balances this up.
There is now preliminary support for Kempston & Sinclair joysticks.
A USB hub can be connected to the RP2040 allowing a keyboard and joysticks to be used with the Spectrum. The code is a bit new and I don't know how many different joysticks will be supported; if you are having trouble raise an issue and attach a HID report descriptor from your device and I will have a look at it.
To get this to work I have done some hacking and slashing in TinyUSB (sorry Ha Thach):
https://github.com/fruit-bat/tinyusb/tree/hid_micro_parser
update
Updates suggested by Ryzee119 are getting harder to merge into the latest code:
https://github.com/Ryzee119/tinyusb/tree/multi-hub
The combined efforts were here, but are now out of date:
https://github.com/fruit-bat/tinyusb/tree/hid_micro_parser_and_hub
Try it
A pre-built binary can be copied directly to a Pico Pi. Connect your Pico Pi with a USB cable, while holding down the program button, then:
cp ZxSpectrum.uf2 /media/pi/RPI-RP2/
Build
The version of TinyUSB in the Pico SDK will need to be replaced with a version containing a HID report parser and USB hub support.
Using git protocol:
cd $PICO_SDK_PATH/lib/
mv tinyusb tinyusb.orig
git clone git@github.com:fruit-bat/tinyusb.git
cd tinyusb
git checkout hid_micro_parser
...or using https protocol:
cd $PICO_SDK_PATH/lib/
mv tinyusb tinyusb.orig
git clone https://github.com/fruit-bat/tinyusb.git
cd tinyusb
git checkout hid_micro_parser
The following code needs to be cloned into the 'apps' folder of the PicoDVI library.
Using git protocol:
cd PicoDVI/software/apps
git clone git@github.com:fruit-bat/pico-zxspectrum.git zxspectrum
git clone git@github.com:fruit-bat/no-OS-FatFS-SD-SPI-RPi-Pico.git
git clone git@github.com:fruit-bat/pico-dvi-menu
git clone git@github.com:fruit-bat/pico-emu-utils
...or using https protocol:
cd PicoDVI/software/apps
git clone https://github.com/fruit-bat/pico-zxspectrum.git zxspectrum
git clone https://github.com/fruit-bat/no-OS-FatFS-SD-SPI-RPi-Pico.git
git clone https://github.com/fruit-bat/pico-dvi-menu
git clone https://github.com/fruit-bat/pico-emu-utils
In the 'apps' folder add the following lines to CMakeLists.txt
add_subdirectory(pico-dvi-menu)
add_subdirectory(pico-emu-utils)
add_subdirectory(zxspectrum)
add_subdirectory(no-OS-FatFS-SD-SPI-RPi-Pico/FatFs_SPI)
If your board does not include SD card detect add the following line in the file "zxspectrum/src/hw_config.c":
.use_card_detect = false,
after the line:
.card_detected_true = 1
In the build folder:
cmake -DPICO_COPY_TO_RAM=0 ..
make clean
make -j4 ZxSpectrum
cp apps/zxspectrum/ZxSpectrum.uf2 /media/pi/RPI-RP2/
Prepare an SD card
The following folders need to be created on the SD card:
| Folder | Contents |
|---|---|
| zxspectrum/snapshots | Put your .z80 snapshot files in here. |
| zxspectrum/quicksaves | Folder for quick saves. |
| zxspectrum/tapes | Folder for .tap tape files. |
Special keys
| Key | Action |
|---|---|
| AltGr | Symbol |
| F1 | Toggle on screen menu |
| F4 | Toggle the Z80 moderator. Cycles through 3.5Mhz, 4.0Mhz and unmoderated |
| F5 | play current tape |
| F6 | play previous tape |
| F7 | play next tape |
| F8 | Reload current snap |
| F9 | previous snap |
| F10 | next snap |
| F11 | Reset as 48k Spectrum |
| F12 | Reset as 128k Spectrum |
| LCtrl + F1-F12 | Quick save (LCtrl+F1 = save slot 1, LCtrl+F2 = save slot 2, etc) |
| LAlt + F1-F12 | Quick load (LAlt+F1 = load slot 1, LAlt+F2 = load slot 2, etc) |
Missing features
- Audio input
Debug
| Pico pin | Pico GPIO | Adapter wire |
|---|---|---|
| 1 | GP0 | White |
| 2 | GP1 | Green |
| 3 | GND | Black |
tio -m ODELBS /dev/ttyUSB0
Thanks to
CarlK for the super no OS FAT FS for Pico
Damien G for maintaining and publishing some wonderful 8-bit fonts
Wren for the amazing PicoDVI
hathach for the embeded USB library TinyUSB
Lin Ke-Fong for the Z80 emulator
References
Wren's Amazing PicoDVI
Z80 file format documentation
Fonts by DamienG
http://www.breakintoprogram.co.uk/computers/zx-spectrum/screen-memory-layout
http://www.breakintoprogram.co.uk/computers/zx-spectrum/keyboard
http://www.breakintoprogram.co.uk/computers/zx-spectrum/interrupts
http://mdfs.net/Software/Spectrum/Harston/
https://www.1000bit.it/support/manuali/sinclair/zxspectrum/sm/section1.html
https://k1.spdns.de/Vintage/Sinclair/82/Sinclair%20ZX%20Spectrum/ROMs/gw03%20'gosh%2C%20wonderful'%20(Geoff%20Wearmouth)/gw03%20info.htm
https://worldofspectrum.org/faq/reference/48kreference.htm
https://worldofspectrum.org/faq/reference/128kreference.htm
http://www.zxdesign.info/cassette.shtml
https://uelectronics.info/2015/03/21/zx-spectrum-and-loaders-part-one/
https://mdfs.net/Software/Spectrum/ROMImages/
https://worldofspectrum.org/ZXSpectrum128Manual/sp128p13.html
https://cpctech.cpc-live.com/docs/ay38912/psgspec.htm
http://www.armory.com/~rstevew/Public/SoundSynth/Novelty/AY3-8910/start.html
USB HID 1.1