Raspberry Pi - Rocnetnode

I have been looking for a way to integrate the Raspberry Pi into my railway electronics without too much extra tinkering, and in a way that would integrate into my existing systems. Luckily, RocRail’s Peter Gilling has seen the advantage of Raspberry Pi’s, and made a couple of wonderful kits that expand the raspi’s possibilities: they use the i2c bus, that is available on the pi’s interface connector, boost it using the Philips P82B715 chip (a i2c transceiver), so it can be used over longer distances, and then use 2 MCP23017 chips to get 32 additional inputs and outputs.

These can be used for all conceivable purposes:

• feedback, by connecting it to a sensor, like a hall transistor, or current sensing circuit
• output, to switch anything on or off; directly with leds, or indirectly by using relays or MosFets
• effects, by programming the output to blink
• anything else, by combining things using Macros.

All this functionality is offered through rocrail, by installing the 'rocnetnode' package on a Raspbian Wheezy image, or just use the prepared image also available at www.rocrail.net. The raspis are connected though ethernet or wifi (the first is recommended), and they show up as soon as the software starts. You can configure everything from the Rocrail program.

First Kit: CGA-Pi01

This kit connects directly to the raspi’s P1 connector, and features a pushbutton to configure the node, 2 leds, and a connector to connect the I/O modules. The only active component on this kit is the i2c transceiver.
Another great option is the USB connector: the interface modules can be connected through USB to get the 5V needed to power them, but you can route this power all the way back to the raspi. So to get the rocnetnodes working you only need 2 connections for the system: ethernet and USB.

Second kit: CGA-Pi02

This kit features a i2c transceiver, 2 MCP23017 chips, 2 connectors to connect to the CGA-pi01 and a next I/O board. With the dip switches the address of the module is selected, this way 4 modules can be used on one bus, for a total of 4 x 32 = 128 per raspi. Another great option is the USB connector: the interface modules can be connected through USB to get the 5V needed to power them, but you can route this power all the way back to the raspi. So to get the rocnetnodes working you only need 2 connections for the system: ethernet and USB.