Do you know the OMEN Alpha? Bravo is a 65C02-based brother of this SBC. It was made for educational purposes, so kept as simple as possible.
P.S.: You can get your own Bravo kit on Tindie.
- 65C02 CPU by Rockwell operated at 3.6864 MHz (You can use the WDC version too)
- 32 kB of static RAM
- 8 kB of EEPROM (in fact, you can use up to 32 kB chip. You can select one of two banks by a switch)
- ACIA 6551 for serial port, provides serial communication up to 19.200 Bd
- VIA 6522 (new from issue 3) - 2x parallel port, 2x timer/counter, shift register
- A "System Bus Connector" with data bus, address lines, control lines and decoded I/O addresses.
The very first batch of prototype PCBs should arrived next week. I am really looking forward for it!
PCB Issue 2
Oh my... The latter is better. First version of PCB has a big issue with oscillator, based on 74HC14. In the second issue I have changed a lot of things: I have used the internal oscillator, I have removed the 65C22 VIA (there's more space on a board now, so routing is more easy) and I have moved the system connector. Issue 2 looks much better, and the best thing is: it works! It works on the very first power up!
Easy, simple, 6 ICs...
The First Power Up...
It seems everything works, but no sane signal on the serial output appears. I have connected the logical analyzer, but everything was OK: the clock signal, the address decoder, RD/WR glue logic...
And suddenly I saw it! The firmware I have loaded in that EEPROM was for the first issue: the LED blinking via the 65C22 VIA. Issue 2 has no VIA. So it took only few minutes to write a new code, burn it into the EEPROM, and voila, it works!
PCB Issue 3, 4
Issue 3 added the VIA chip - Versatile Interface Adapter R6522. It provides two serial ports, two 16bits counters / timers and a shift register for parallel-to-serial conversion and vice versa.
Unfortunatelly, Issue 3 has an error - ground was not connected together and there were missing place for the resonant capacitor and load, so some CPUs won't work. You can solder one wire and a two parts directly to the PCB, but it is not a solution, so I designed an Issue 4 PCB with all of those bugs fixed.
Buy your own OMEN Bravo
Of course, I have a few pieces of Bravo in stock. (Issue 4 and a discounted Issue 3)