If we like to have a really small DCC accessory decoder that sets us back just some $2,50, the ATTiny might just be it.
Of course we could use a plain ATTiny chip and solder it onto a small piece of experiment baord together with the optocoupler circuit needed to transfer the track DCC voltage to 5V TTL. But then we’d have to figure out how to program the thing. Not really difficult, but still more work than when we’d use the new ATTiny USB boards that are available nowadays.
This is an example of such a board. The dimensions are just 22×18 mm and it contains the ATtiny, a few LED’s, a power converter that allows up to 16V input and a mini USB port. The boot software to make this USB work and allow connection to the Ardiuiono IDE is already baked into the chip. The hardware can be found here.
There is no USB-serial chip on the board, it relies on the software inside the ATTiny. While it worked with both my PC’s, there is no guarantee it works with every PC. The process of installing the software and drivers and get it to work with your Arduino software development IDE is described here.
The ATTiny DCC accessory decoder software can be downloaded here. The schematics for the optocoupler circuit needed to transfer DCC track voltage to TTL can be found on the Software page.
The USB driver is inclued in the zip file, in case the process described at the digistump site did not work (which happened with me with one of the PC’s).
The video shows the ESU ECoS sends out a DCC accessory address, that controls pin 1 of the ATtiny, which has the on board LED attached.