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next steps are done: 1st – changed the connectors from the above mentioned “Ax” into Dx” (X1/12..17, X2/12..13) and everything works well.
2nd – so far so good – but why use so many ports? try i2c also for keypad, as we already do have a 20*4 LCD on the bus. Buy pcf8574, connect and check with small test sketches. Everything works fine!
3rd – get into the “real” sketch and … the above mentioned “rogue 1” returns! and the i2c bus freezes, at least regarding the keypad. the LCD is furtheron useable by functions executed from other input sources, especially via ethernet.
It’s not from the other included libraries (ethernet, controllino, accelstepper, spi, eeprom). These I can also include into the working test sketches.
in some other forums i found the bus wiring length as reason mentioned, which might be preventioned by pull-up resistors. but that i first must discuss with my electronis guru before i grill the chips …
btw: wiring might be much shorter if the different designers of the interface boardlets had not interchanged the sequence of vcc and gnd, then i just could piggyback them … so i do need another length of strips in between them
