ZX Spectrum on Tang Nano 9k devboard

Yet another ZX Spectrum clone on Sipeed Tang Nano 9k development board.

The firmware is still under heavy development. Border effects works incorrectly yet.

Implemented hardware

• HDMI output at 720x576 (49Hz)
• Analog sound output
• USB Keyboard
• Z80 Soft CPU (T80a)
• DivMMC with ESXDOS 0.8.9
• Turbosound (2x AY3-8010)
• Soundrive

How-to make it running

1. Install openFpgaLoader tool
2. Upload ROM image rom/rom-tang9k-speccy.rom into the external SPI flash by openFPGALoader -b tangnano9k --external-flash rom/rom-tang9k-speccy.rom
3. Upload bitstream into the internal flash openFPGALoader -b tangnano9k -f impl/pnr/tang9k-speccy.fs
4. Connect USB keyboard (+5V, GND as well as D+, D- signals via 33 Ohm resistors)
5. Prepare the SD card (FAT32, ESXDOS 0.8.9)

HDMI tips

Some monitors and TVs do not show a picture over the Tang Nano HDMI connector. In this case you need to add a solder bridge instead of R1 (https://www.eevblog.com/forum/fpga/fpga-to-hdmi-variants/msg4613152/#msg4613152).

Controls

• F1 - Pentagon 128 with ESXDOS 0.8.9

• F2 - Pentagon 1024 with Z-Controller

• F3 - Retroleum DiagRom

• F4 - Test firmware with RAGE umbrella

• F10 - CPU reset

• F11 - NMI

• F12 - Reset

Debug controls

• F5,F6 - Move INT horisontal position
• F7,F8 - Move INT vertical position

TODO

1. Refactor a videocontroller, implement it via a classic scheme with the scandoubler
2. Add i2c RTC and optionally i2c eeprom
3. Add ESP8266 module support via ZXUNO UART / AY UART or ZiFi UART standard
4. Add USB mouse as kempston mouse
5. Add USB gamepad as kempston joystick
6. Implement more video modes (like Timex hires, ULA+, etc)
7. Add Tape in/out
8. Create an addon PCB (motherboard?) for advanced peripherial

Minimal breadboard setup

Pinout (WIP)

               -----------------
              | S2    USB    S1 |
              |                 |
 (SD CS)  ----| 38     T     63 |---- x
 (SD SI)  ----| 37     A     86 |---- x (*1V8)
 (SD SCK) ----| 36     N     85 |---- x (*1V8)
 (SD SO)  ----| 39     G     84 |---- x (*1V8)
 USBK D-  ----| 25           83 |---- x (*1V8)
 USBK D+  ----| 26     N     82 |---- x (*1V8)
 DAC R    ----| 27     A     81 |---- x (*1V8)
 DAC L    ----| 28     N     80 |---- x (*1V8)
 WIFI TX  ----| 29     O     79 |---- x (*1V8)
 WIFI RX  ----| 30           77 |---- x
 WIFI CTS ----| 33     9     76 |---- x
 USBM D-  ----| 34     K     75 |---- (HDMI D2P)
 USBM D+  ----| 40           74 |---- (HDMI D2N)
 USBJ D-  ----| 35           73 |---- (HDMI D1P)
 USBJ D+  ----| 41           72 |---- (HDMI D1N)
 TAPEIN   ----| 42           71 |---- (HDMI D0P)
 TAPEOUT  ----| 51           70 |---- (HDMI D0N)
 BEEPER   ----| 53           5V |---- 5V
 I2C SDA  ----| 54           48 |---- x
 I2C SCL  ----| 55           49 |---- x
 32KHZ    ----| 56           31 |---- x
 SQW      ----| 57           32 |---- x
 (HDMI CKN) --| 68          GND |---- GND
 (HDMI CKP) --| 69          3V3 |---- 3V3
              |                 |
              |       HDMI      |
               _________________