The AVI ELF II Rev D Variant is a reproduction of the RCA CDP1802-based computer kit by Netronics Research and Development Limited.
The AVI ELF II Rev D Variant single board microcomputer is a replica of the Netronics ELF II microcomputer that was reimagined by the late Ed Keefe (1964-2022) to maintain the aesthetic of the original ELF II, with additional onboard RAM and daughter cards for flexibility of keypad encoders and display drivers.
This project is ongoing with the support of Josh Bensadon, Andrew Wasson, Walter Miraglia, Costas Skordis and Rizal Acob. Below you will find a stable version of the PCB gerber files, bill of materials.
The Assembly Manual is in the Wiki.
There are a number of differences between the AVI ELF II and the original:
- Power on/off toggle switch with power status LED.
- Power is from a single 6 to 9 volt DC supply that supplies the board and expansion cards. Suitable for use with typical 9 volt adapter with barrel connector (center positive). If a V7805-2000R (DC DC CONVERTER 5V 10W) is used in place of the LM7805 voltage regulator, up to 2A of current is available for the board and expansion boards.
- Optional on-board DC-DC coverter for +8 volt / -8 volt supply for original Netronics Giant Board.
- 32KB on-board RAM with ability to adjust RAM size from 256 Bytes to 32KB.
- Optional onboard RAM battery backup.
- Keypad uses modern Cherry MX compatible keyswitches.
- The keypad input switch has improved debouncing over the original ELF II keypad.
- Optional raised Keypad to approximate height of keypad on the original Netronics ELF II.
- Onboard Data Display options for original HP 5082-7740 7-Segment Displays or HP 5082-7340 Dot Matrix LED Display.
- Optional raised display boards for TIL 311 or Dot Matrix Address and Data Displays.
Initially, we approached this project with the goal to faithfully reporduce the original Netronics ELF II with added flexibility to choose several LED display types, maximize user RAM for programs and use modern keyswitches. We also planned to add a modern equivalent of the Netronics Giant Board called the Hyperboard. As we workeed through development and testing, we realized that the ELF II provides the perfect springboard to support a variety of 1802 powered systems.
A faithful reproduction of the original ELF II
If all you are looking for is a journey back to the late 70's, with a trusty ELF II and all of the RAM you could possibly use then, the AVI ELF II main board is all you need. It will respond and function as an exact replica of the original and if you squint at it from several feet away, it looks pretty close to the real McCoy. If you want to have the expansion possibilities that you would have enjoyed with the original system expanded with a Netronics Giant Board and the Giant Monitor, you can add a AVI Hyperboard to the mix.
An ELF2K compatible ELF/OS machine with the Aesthetics and features of the ELF II platform
Uses the STG ELF2K to ELF II board and AVI ELF II TIL311 6-Digit Display Card described below.
More details to come...
An RCA VIP Capable ELF II
Uses the ELF II SD Card and VIP Keyboard For ELF II described below. Optionally add Cassette Board for loading and saving to cassette tape.
More details to come...
An RCA Studio II Capable ELF II
In development. Will require the VIP Keyboard for ELF II and secondary VIP Keyboard for ELF II + the Hyperboard or ELF II SD Card board.
More details to come...
Aside from the novelty of having a retro-replica of one of the most sought after Cosmac ELF variants, the fun begins when you add expansion boards to add features and extend the capabilities of the ELF II microcomputer. Several Expansion boards have been designed to enhance and extend the ELF II. These were designed primarily for use with the AVI ELF II but it is quite possible that many will work with an orginal Netronics ELF II.
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AVI Hyperboard Expansion Card
The Hyperboard is a modern take on the Netronics ELF II Giant Board which includes additional RAM and EEPROM, input/output ports and serial connections with 32KB RAM / 32KB EPROM, CD1852 Byte-Wide Input/Output Ports, CD1854 UART, Cassette IN/OUT with proto area.
If the goal for your AVI ELF II is a fully expanded period computer from the late 1970's, the Hyperboard is a good addition to begin with. The Hyperboard will run new firmware readily and also runs period software including the Netronics Giant Monitor for automating entry, inspection and running programs. The Hyperboard also enables loading and saving programs from cassete tape. -
STG ELF 2K Disk for ELF II Card
Uses Spare Time Gizmos ELF 2K Firmware to add a Compact Flash Card "Hard Disk" to use with the ELF/OS Disk Operating System. Provides 32KB RAM / 32KB EPROM, 16C450 UART, Serial Communications with FTDI connections, USB FT232RL device, IDE connection, CF Card socket and Real Time Clock chip.
If the goal for your AVI ELF II is to have a retro-modern 1802 system capable of running the ELF/OS disk operating system, using a compact flash card as a hard drive with a RS232 Serial connection up to BAUD 19200 and a real time clock, the ELF 2K for ELF II card covers all of the bases to get you there and the STG firmware provides additional system tools and programming languages. -
ELF II SD Card
With 128K RAM, 32K EEPROM, TTL and Serial terminal connections and an SD Card for storage, the ELF II SD Card board provides the electronics and software to turn your AVI ELF II into a powerful RCA VIP compatible machine that is capable of reading, loading and running your software library of VIP and Chip8 programs just like the original RCA VIP.
Note: For full VIP compatibility, the VIP Keyboard For ELF II described below is required.
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ASCII II Keyboard Rev D
In development and coming soon... The ASCII II Keyboard Rev D is an amalgamation of the two ASCII keyboards that were made available for the Netronics ELF II and Explorer 85 single board computers. The Rev D board can operate as a stand alone keyboard with its onboard ac/dc power supply or it can be supplied the +5, -12v & GND from an ELF II equipped with a Giant Board or Hyperboard. With the addition of the ASCII II keyboard and a Giant Board + RAM Boards or the AVI Hyperboard, your ELF II will be able to load Netronics Tiny Basic from cassette and use the ELF II onboard Pixie display chip just as you would in 1979.
- Get the schematics here
- Get the BOM here
- Gerber files being finalized
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VIP Keyboard For ELF II
The VIP Keyboard for ELF II is the companion card for the ELF II SD Card described above, providing the correct keyboard orientation and mapping for the RCA VIP system with a Q LED and a micro speaker to play the beeps tones and notifications that the original VIP plays.
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VIP Secondary Keyboard for ELF II
For use with VIP Keyboard for ELF II as shown above for multiplayer game support.
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AVI ELF II Cassette Interface Card
An expansion card to add the ability to load and save programs to cassette tape using the Cassette In | Out jacks on the ELF II main board or Cassette In | Out on the cassette board itself. This makes a useful companion board for the ELF II SD Card for loading and saving VIP programs and data to cassette.
- Get the schematics here
- Get the Gerber Files here
- Build Notes and Assembly Manual in progress.
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Protoboard
Full sized expansion card with 86 position edge connection for prototyping cicuitry.
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ELF II LED Matrix Display
A plugin display board that is located directly in front of the Hex keypad, replacing the original LED data display to provide an updated, larger, dot matrix display with 4 digit address and 2 digit data, plus additional messaging to indicate load mode and reset.
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AVI ELF II TIL311 6-Digit Display Card
A plugin display board that is located directly in front of the Hex keypad, replacing the original LED data display to provide a 6-digit display using the TIl311 displays with 4 digit address and 2 digit data.
Note: TIL311 displays draw a lot of current. We highly recommend using the V7805-2000R in place of the LM7805 voltage regulator on your ELF II Main Board if you add the 6-Digit Display Card to your system; the V7805-2000R runs extremely cool even when powering the ELF II Main Board + TIL311 6-Digit Display Card + an expansion card like the Hyperboard or STG ELF 2K Disk for ELF II Card. If you choose to use an LM7805 regulator, make sure to use a decent heatsink to dissipate the heat and do not leave your system unattended when powered on.
