10x10cm PCB variant of ZX-Uno project

[More photos]

Tech specs:

• Fully compatible with ZX Uno v4.1 and ZX-Uno VGA 2M
• XC6SLX9 FPGA
• 2Mb SRAM memory
• VGA video output
• PAL/NTSC video + audio output via 3.5 jack connector (raspberry-pi compatible pinout)
• PS/2 keyboard and mouse ports
• 2xDB-9 ports for Atari-compatible joysticks
• SD/microSD card slot
• Tape input via Bluetooth module or ordinary 3.5 jack
• MIDI
• WiFi module
• RTC (starting from rev.B)
• Type C (starting from rev.D) or MicroUSB power supply
• Board optimized for G738 and G706 cases

FAQ on official site: link

Some random photos: link

• Rev.A - first release (main pcb errata and covers errata).
• Rev.A1 - fixes all known issues of rev.A.
• Rev.B:
  • added RTC
  • changed second joystick port wiring - in rev.A it's has been wired like in ZXUNO-VGA2M, but now it's wired like Joysplitter, which is officially supported way
  • joysticks are now powered by +5V rail instead of +3.3V - this should improve compatibility with various RF gamepads
  • optimized SAM2695 footprint for hand soldering
  • added opamp for proper MIDI sound mixing
  • added buffer in DAC circuit
  • added separate LDO for SD card and WiFi module
  • added resistor between WiFi's GPIO15 and GND to prevent IC heating
  • remove beeper (which wasn't used anyway)
  • improved power distribution for FPGA chip
  • pcb corners are rounded now
  • experimental tape-in circuit
• Rev.C:
  • added dedicated LDO for audio to improve noise floor
  • added optional capacitor for NTSC quartz stability
  • added missing decoupling capacitor on RTC power rail
  • added current-limiting resistors after opamp on sound output
  • changed R76, R80 from 10kΩ to 8.2kΩ
  • changed U10 opamp from NE5532 to LMV358 as it better suited for low-voltage operation
  • 3mm front leds replaced by 5mm
  • experimental reset circuit based on MAX809
  • reverted to old tape-in circuit
• Rev.D:
  • used USB Type C instead of Micro USB
  • PJ-320 3.5mm jack replaced by PJ-322
  • added solder jumper to select 3.5mm jack CVBS pinout
  • MIDI synthesizer U6 uses clean analog power rail now
  • improved W25Q128 footprint to able to install IC in WSON package
  • some minor PCB layout changes to reduce WiFi interference
  • reverted to old reset circuit
• Rev.D1:
  • changed R16 from 220Ω to 1kΩ to reduce power led bightness
  • changed R70, R71 from 10kΩ to 12kΩ to improve balance with AY
  • changed C51 from 100nF to 1uF to improve audio noise floor
  • changed C13 value as some quartz failed to start with 4.3pF load
  • changed U17 from LP2985-3.3 to TPS7A2033PDBVR due to better PSRR
  • changed U15 from 74LVC2G34 to 74LVC2G04 as it's more common in my projects

• ZX Uno official site: link
• ZX Uno VGA 2M: link
• Great collection of cores, games and much stuff for ZX Uno: link, in english