pico-zxspectrum

It's been 40 years... I still remember the computery smell when I unboxed mine at Xmas (I think 1983)

So for old times' sake here's a ZX Spectrum emulator for the Raspberry Pi pico, using:

screen: a 5cm 320x240 TFT display as screen.
keyboard: USB serial connection
sound: not sure yet...
cassette recorder: life's too short...

Status

display: fully operational
keyboard: serial works using a basic python client
sound
real-time(?) tape loading
image loading over USB serial: Z80 and SNA formats supported
image saving over USB serial: Z80 format
save screenshot over USB serial: png format

Dependencies

Requires pico-sdk (and its dependencies e.g. tinyUSB...), plus the pimoroni-pico libraries. In the repo root:

Ensure tinyUSB sources are present in the lib subdir of the SDK (extract or symlink to a release here, or use git submodules), e.g.

cd pico-sdk-1.5.1/lib
rmdir tinyusb # will be empty initially
ln -s ../../tinyusb-0.14.0 tinyusb

Using tinyusb 0.15 or above results in a linker error that I don't know how to fix:

[100%] Linking CXX executable picozxspectrum.elf
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: picozxspectrum.elf section `.bss' will not fit in region `RAM'
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: region RAM overflowed
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: section .stack1_dummy VMA [0000000020040000,00000000200407ff] overlaps section .bss VMA [0000000020001828,000000002004005f]
/usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: region `RAM' overflowed by 96 bytes
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/picozxspectrum.dir/build.make:1447: picozxspectrum.elf] Error 1
make[1]: *** [CMakeFiles/Makefile2:1541: CMakeFiles/picozxspectrum.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

Configuration

Symlink Pico SDK and Pimoroni Pico:

ln -s ../pico-sdk-1.5.1 pico-sdk # adjust version and location as necessary
ln -s pico-sdk/external/pico_sdk_import.cmake
ln -s ../pimoroni-pico # adjust to wherever you cloned it to

Build

mkdir -p build && cd build
cmake -DPICO_SDK=../pico_sdk ..
make -j

Install

Still in the build directory:

cp picozxspectrum.uf2 /media/$USER/RPI-RP2/

You should see at this point a blank screen with the LED bright white.

Use

Interaction requires a (rudimentary) keyboard driver written in python and depends on pyserial and pynput. It can also load an image (Z80 or SNA) on startup:

python zx.py [image]

Keys map closely to the ZX Spectrum keyboard (below), with LShiftas caps shift, RCtrl is symbol shift. LShift+RCtrl enters extended mode. Various unmapped keys also work, such as Backspace and the arrow keys which emulate caps-shifted 0,5,6,7,8 respectively.

~~PrtScr~~Home triggers a screenshot save (png format)

Ins triggers an image save (registers and RAM in Z80 format)

Del or the screen's X button resets the device to the last image loaded/saved, or ZX basic.

Esc followed by Ctrl+C exits the keyboard listener.