Heathkit Hero - swindonmakers/wiki GitHub Wiki
Note: There is a blog post relating to this project.
The Museum has allowed us to hack on an old Heathkit Hero, more specifically, the Hero 1, AKA ET-18. From the testing procedures, everything appears to work except moving the motors -- which is currently diagnosed as bad batteries.
I've taken photos of the schematics, though I have yet to post them online (they still have an active copyright holder -- Heathkit sold the copyright to the manuals). From that, I think that my original plan of driving the robot from the experiment board won't work -- the experiment board doesn't have direct access to the other perpherials, so we'd have to write driver code on the main CPU to implement a protocol over the experiment board, instead of driving things directly. However, a number of debug headers seem to exist on the CPU board, which may be powerful enough to essentially replace the CPU without modifying the hardware.
While writing the below, I found this, which may describe the best route forward.
Headers:
P406, on CPU board -- buffered address box, low bits:
- low when VMA high and address bits a15:a13 = 2 (a14 high) -- VMA=valid memory address -- 0x4000-0x5FFF
- low when VMA high and address bits a15:a13 = 3 (a13, a14 high) -- 0x6000-0x7FFF
- BA7
- BA6
- BA5
- BA4
- BA3
- BA2
- BA1
- BA0
P408, on CPU board -- buffered address box, high bits:
- low when VMA high and address bits a15:a13 = 4 (a15 high) - 0x8000-0x9FFF
- low when VMA high and address bits a15:a13 = 5 (a15 and a13 high) - 0xA000-BFFF
- BA15
- BA14
- BA13
- BA12
- BA11
- BA10
- BA9
- BA8
P407, on CPU board -- unbuffered data bus (note: numbers not marked on schematic, so are guess):
- R/W line, notted and buffered? -- after not, high=write, low=read
- !RESET
- D7
- D6
- D5
- D4
- D3
- D2
- D1