vossstef / tang_nano_9k_6502

6502 SBC in a Gowin GW1NR-9 FPGA on a Sipeed Tang Nano 9k

tang_nano_9k_6502

A 6502 SBC in a Gowin GW1NR-9 FPGA on a Sipeed Tang Nano 9k.

Ported ricktw project 6502_HDMI to a Tang Nano 9k
Further description of the original project over here using sources from display_controller and vt52

Features

• HDMI Video Output 640x480
• VT52 Terminal 80x25
• MS BASIC
• PS/2 Keyboard
• RAM 4K

ToDo at Startup

A green blinking cursor will apear.
Cold[C] or warm [W] start ?
Answer by a 'c' keypress
MEMORY SIZE?
Answer by typing 4095
TERMINAL WIDTH?
Answer by typing 80
System shall response with BASIC xy and OK promt

Tang Push Button utilization

• S1 push button Reset

Powering

Prototype circuit with Keyboard can be powered by Tang USB-C connector from PC or a Power Supply Adapter.

Synthesis

Source code can be synthesized, fitted and programmed with GOWIN IDE Windows or Linux.

Pin mapping

see pin configuration in .cst configuration file

HW circuit considerations

• PS/2 keyboard has to be connected to 3.3V tolerant FPGA via level shifter to avoid damage of inputs ! Use e.g. 2 pcs SN74LVC1G17DBVR 5V to 3V3 level shifter. My Keyboard has internal pull-up resistors to 5V for Clock and Data Signals so didn't needed external ones.
• Tang Nano 5V output connected to Keyboard supply. Tang 3V3 output to level shifter supply.

Pinmap PS2 Interface

PS2 pin	Tang Nano pin	FPGA pin	PS2 Function
1	J6 10	77	DATA
2	n.c.	-	n.c.
3	J6 23	-	GND
4	J6 18	-	+5V
5	J6 11	76	CLK
6	n.c.	-	n.c

BOM

Sipeed Tang Nano 9k
PS/2 Keyboard
PS/2 Socket Adapter Module
2 pcs SN74LVC1G17DBVR level shifter
Prototype Board

tang_nano_9k_6502's Issues

Flashing cursor only, no response from keyboard

Hello. This project seemed to build ok but when I run it I just get a flashing green cursor and nothing else.

Keyboard, monitor and Tang Nano 9k all work perfectly with your VIC-20 project so doesn't seem like hw issue.

Not sure if the basic ROM is loading? Not sure where I should start with troubleshooting.