I have been looking at the datasheet for a MCP23017 I2C I/O expander chip (16 GP I/O pins). https://www.adafruit.com/product/732 it supports addressing of up to 8 chips on the same I2C bus, giving you 128 pins to work with. the downside is, it uses a lot of external hardware, and a lot of soldering (may be a hang-up for some users). I am still playing with the idea of RS485 too, as it is easier to expand, but more work to solder, and i have to create an arduino library to make it work. Personally, i would be fine with the MCP23017, and 128 ports. i was thinking of using just a computer network to create a cluster of possible devices. something that just needs an arduino Mega 2560, and an ethernet/WiFi shield. but as i am already using an ethernet shield for command, i will have to read up on examples to see it an arduino can use two concurrent connections. the remote modules would run as servers, and the DCC++ master would be a client and poll each device. it could potentially be a nightmare to configure though. Just thinking out loud mainly. Once my layout "grows up", i will have a better test platform. having a bit of a struggle financially in pulling it all together. ~Travis
Actually if your looking for just inputs and outputs most of the work is done.. There is a project on utrainia.com that uses an Arduino and has it emulate the CMRI interface. All the files are available on GitHub too. You would just need to create another connection in JMRI for CMRI. The utrainia site also has some info about expanding the I/O of any Arduino which could be added to the DCC++ base station code. It is worth reading. Gregg posted before about why the I2C is not a good idea, mainly because it consumes a lot of processing time. This can interfere with keeping the DCC signal going.
I think we need a feedback bus instead of another hardware for IOs such as S88 or ExpressNet, this way it simplifies the wiring for our layout. Thanks
