search

mlorenzati / pico-rgb2hdmi

A microprocessed RGB to HDMI Converter with USB capture
MIT License
70 stars 11 forks source link

MDA/Hercules Support #34

Open charlysan opened 1 year ago

charlysan commented 1 year ago

Introduction

The purpose of this issue is to start a discussion about MDA/Hercules implementation.

Requirements & specs

Specs

Feature IBM MDA Hercules Graphics Card (HGC)
Text Mode 80x25 characters (720x350 pixels) 80x25 characters (720x350 pixels)
Graphics Mode None 720x348 pixels
Vertical Sync Frequency 50 Hz 50 Hz
Horizontal Sync Frequency ~18.432 kHz ~18.432 kHz
Signal Type TTL Digital TTL Digital

DB9 Pinout

Pin number IBM MDA Hercules Graphics Card (HGC)
Pin 1 Ground Ground
Pin 2 Ground Ground
Pin 3 Not connected Not connected
Pin 4 Not connected Not connected
Pin 5 Not connected Not connected
Pin 6 Intensity Intensity
Pin 7 Video Video
Pin 8 Horizontal Sync Horizontal Sync
Pin 9 Vertical Sync Vertical Sync

Video - Intensity signals

Video Intensity Resulting 'colour'
0 0 Black
0 1 Dim
1 0 Normal
1 1 Bright

Docs:

Implementation

Hardware

We could connect Video to Rin, and Intensity to Gin for example.

What about 18 KHz support?

Software

TBD