Stern Trough Opto Board reading succeeded

[Dorus van der Linden]

Hi everyone,

After a few years I have finally been able to read the Stern Trough Opto Board for my home brew machine.

I have figured out that the serial latch is inverted

'RCK' does not go straight to the 74HCT165's `SH/LD`. The board sends it through a spare channel of the inverting 74HC540 first. 

To read the board:

1. Keep `RCK` low while idle.
2. Pulse `RCK` high for a few microseconds, then set it low again.
3. Clock 8 bits (SPI mode 0, MSB first) and read `MISO`.

I have build a small AtMega circuit with Arduino code to read the opto-serial and output individual switch pins (used for connecting to your favorite control boards).

I tested OPP red-boards & CobraPin and both work.

I have (with AI support) written a post about that I can send if someone needs it, or I could and to MPF documentation. 

Any interest?

Best, Dorus 
PS: my home brew is really improving now.