In the previous post about using the Arduino as an S88 sensor interface, I only had 1 Arduino available for test, which restricted the test to max 16 inputs and it was not possible to see if ‘chaining’ multiple Arduino’s would work.
In the mean time a new batch of Arduino’s has arrived from Aliexpress. making a test with multiple Arduino’s in ‘chain’ possible. To chain them, all that is needed is to connect the ‘data-out’ of the next Arduino to the ‘data-in’ of the previous Arduino. Also, of course, the S88 Clock and PS pulses and GND have to be connected to all Arduino’s in the chain. The 5V power can come from the Command Station S88 bus, connect it not to the power terminal, but to a pin that reads 5V. First check your CS S88 power line has enough ‘juice’, else use an external supply. Power consumption of an Arduino is less than 30mA.
The software seems to be running well. I did have a strange phenomenon with my ECoS2 though. Every time the Arduino starts up, or is reset, the first 8 bits showed up as ‘1’, even though there were no sensor signals. It went to ‘normal’ only after I changed one of the sensor inputs. After a bit of puzzling and trying out different things, I still could not find a cause and a proper solution. So … what I did is have a little extra ‘tweak’ in the software. One second after startup I let the software change bit 0 of the sensors … which does the trick. Not neat … but it works! 🙂
The software can be downloaded here, free for private, non commercial, use. Disclaimer: So far it has only been tested on test-bench scale. Longer term reliability ‘in the field’ with longer wires and possible distorting signals around is not yet proven. Use at your own risk.