Ondra SPO 186 was a Czechoslovak 8-bit computer developed in 1985 at Tesla Liberec by Ing. Eduard Smutný, Ing. Tomáš Smutný and Ing. Jan Mercl as an affordable school and home computer. Tesla produced around 2000 Ondra computers.
This repository contains a Verilog implementation for MiSTer FPGA.

Short demo video of this core

https://youtu.be/YnFbf-u1D80

Older video with load via serial port - not supported anymore
https://youtu.be/B2MRWTKYOYU

Original hardware specifications

CPU U880 @2MHz - East German clone of Z80
64 kB RAM (10 kB used by video RAM)
4-16 kB ROM (EPROM)
TV output
flexible resolution (commonly 322×240 or 322×252; up to ~400×255 possible), black and white, 40 columns × 24 rows
relay for cassette player control - often used for "sound (click) signaling"
Sound: 7 fixed tones (no musical scale)
one 20 pins connector for joystick, Centronics parallel port (8-bit data out, Strobe_n out, Busy in), UART (Reserva In = RXD, Reserva Out = TXD)
cassette player connector for SW load and save at 2400Bd

Keyboard

Ondra has a modest keyboard with only 37 keys, so each key can serve 2 or 3 different characters depending on the modifier key used.

Modifier keys:
Ondra -> PC Keyboard
Shift -> Shift
Symbols -> Alt
Ctrl -> Ctrl
Numbers -> Tab
ČS -> Caps Lock (used for Czech diacritics)

Each modifier key needs to be pressed (and held) before pressing character key. Here is mapping Ondra keys to PC Keyboard. Please note modifier keys are in different colors as invoked characters on other keys.

Graphics generation (Video circuit)

Ondra has a very unique video circuit. Video address counter implemented using two КР580ВИ53 programmable interval timers - Russian clone of i8253. In fact, although Ondra was designed and manufactured in Czechoslovakia, most of ICs were "Made in USSR". Timers are used for generating VSync and HSync start pulses as well as for generating video address itself. Cheap, simple but not easy :) Advantage of this solution is that screen resolution can be programmatically changed. Disadvantage is that CPU must wait while the screen is being drawn. Due to video DMA timing, the CPU is active only a small fraction of each display frame (18–20%).

Implemented features

CPU
64 kB RAM
Keyboard
Sound (7 different sounds - not forming a scale, as on real HW)
Tape load via ADC MiSTer connector (line in)
Ondra SD - modern HW for easier SW load from SD Card
OndraMELODIK - new HW for Ondra bringing better sound using SN76489 chip. Here is link to YouTube video with demo app

Missing features

Ondra SD - RAW R/W support (required for CP/M)

Installation

copy file Ondra_SPO186_########.rbf from releases folder to your MiSTer SD card to Computer folder (######## stands here for date of version - you might want to delete earlier from SD card if you have some)
in MiSTer menu navigate to Ondra_SPO186 item and start the core

Usage

Loading games via Ondra SD

No external HW required - Ondra SD is implemented inside FPGA

Preparing for use

Create "Ondra" folder on your secondary SD card
Copy "__LOADER.BIN" and "_ONDRADM.BIN" to this SD Card from OndraSD.zip
Copy there some games too :) Here is good source https://sites.google.com/site/ondraspo186/d-download/d-1-hry
Your SD Card should look like this

Using Ondra SD

Use ViLi ROM (Ondra greets you with message "Zdraví Vás ONDRA")
type # (ALT + E) and press Enter - if Ondra SD doesn't react press enter again or hold it longer. Or reset Ondra
Ondra File Manager appears in few seconds after several beeps
Choose file or folder and press Enter to change dir or load a file
Shift changes the directory to the root of the SD card

Loading games via audio line in

connect your audio source (cassette player, mobile, ...) to MiSTer ADC (line in)
Choose ViLi ROM
press any key. Screen turn black and will flicker time to time. You can see text ".KÓD 1". This is ok. Ondra turns off the screen to give the CPU more time. Text ".KÓD x" will change as game will be loading to Ondra (x will raise from 1).
start playing WAV file
Enjoy the Ondra SPO 186 and the game :)

README.md Unescape Escape

Ondra SPO 186