Overlay64

overlay64 - video overlay module

The overlay64 module allows superimposing predefined texts onto an existing composite signal or onto the luminance portion of an s-video signal depending on the states of up to sixteen digital input lines. An LM1881 video sync separator IC is used to detect the vertical and horizontal sync pulses of the video signal. An Atmega1284 uses these signals to synchronize with the video signal and to superimpose text on the video display by bit-banging the corresponding characters over SPI.

The user writes a simple configuration file that determines which texts are to be displayed for which input line states. The configuration file is converted to a binary format using the supplied commandline tool before flashing it to the Atmegas's eeprom memory via the USB interface.

Possible uses include displaying the state of control lines for additional hardware installed in a homecomputer such as the Commodore 64, for example to display the currently selected kernal based on the state of the control lines for a multi-kernal adapter.

An early working prototype can be seen in this video where it displays the runtime configuration of the MixSID Stereo SID board:

https://www.youtube.com/watch?v=0exp2yM0WHM

This repository includes the complete sourcecode of the client software, the firmware and all design files in KiCAD format.

LICENSING

Hardware licenced under CERN OHL v.1.2, see ./hardware/LICENSE.txt Software and firmware licenced under GNU GPLv3, see ./LICENSE

The software contains MIT licensed code from https://github.com/arkku/ihex for reading Intel HEX files, Copyright (c) 2013-2015 Kimmo Kulovesi, see ./intelhex/LICENSE

The firmware contains the V-USB Driver (https://www.obdev.at/vusb), (C)2008 Objective Development GmbH.

Distributed in the ./bootloader directory is the USBasp bootloader, (C)2013 Stephan Baerwolf (matrixstorm@gmx.de) and (C)2008 Objective Development GmbH (https://www.obdev.at/vusb).

In compliance with the terms of the (identical) V-USB driver and USBasp bootloader licenses (./firmware/usbdrv/License.txt and ./bootloader/License.txt), the entire project is published under

http://www.henning-bekel.de/overlay64

In addition, this distribution contains

• a circuit diagram in PDF format, see ./hardware/overlay64-schematics.pdf
• the full source code for the host software in ./firmware
• this README file
• references to https://www.obdev.at/vusb

The USB Product and Vendor IDs for the Overlay64 USB device have kindly been provided by OpenMoko, Inc (http://openmoko.org).