florentflament/atari-csync

Generating a clean Atari ST RGB C-Sync signal

An RGB composite sync signal generator for the Atari ST

This repository contains some verilog code to be synthesized and programmed into a Lattice ICE40HX1K FPGA. The main target is csync-predictive-prog; it programs the FPGA, to generate a clean RGB composite sync signal from an Atari ST H-Sync and V-Sync signal. This allows displaying the Atari ST video outout on any RGB compliant display device.

Usage:

$ make csync-predictive-prod

Some other targets are also available (see Makefile), they have mostly been used to perform some experiments.

More context about this project can be found on my Generating a clean Atari ST RGB C-Sync signal article.

Prerequisites

The following Ubuntu / Debian packages are used:

• yosys
• arachne-pnr
• fpga-icestorm
• iverilog (optional)
• gtkwave (optional)

Lattice iCEstick pinout

J2 connector ports:

J2 pin | signal  | FPGA pin
-------+---------+---------
1      | PIO1_02 | 78
2      | PIO1_03 | 79
3      | PIO1_04 | 80
4      | PIO1_05 | 81
5      | GND     |
6      | +3.3V   |
7      | PIO1_06 | 87
8      | PIO1_07 | 88
9      | PIO1_08 | 90
10     | PIO1_09 | 91
11     | GND     |
12     | +3.3V   |

Bottom of iCE40 FPGA stick:

 +-------------+
 |7. . . . . .12
 |1. . . . . .6|
 +-------------+
pin 1

     +-----+
      irda