DCC CV29 Calculator
Within the setup of a DCC controlled locomotive, CV29 seems to cause an inordinate amount of trouble. I think half the blame must go on the makers of throttles which attempt to be "friendly" but fall a bit short and leave their users stuck without a clue what is going on. The other half has to be the lack of school time spent on binary maths :-)
So, what is CV29 ? After the address of the decoder, its probably the most important CV, and because its been like this for a while, we're stuck with it controlling multiple things. It's best thought of as eight on/off or yes/no settings. They can be selected in any combination, and most decoders only use five of the settings. The settings determine whether the decoder responds to 14 step or 28/128 step instructions, whether there is a short (two digit) or long (four digit) address, the type of speed curve, and reverses the direction which is "forwards". Many "my loco doesn't work" problems are traced back to incorrect values in CV29, for example: loco doesn't respond to 4 digit address (bit 5), erratic running or lights not working (often caused by bit 1).
The calculator below shows how it is constructed, and by ticking the boxes associated with the features required, it will calculate the decimal value required for CV29. Or you can put a value for CV29 (eg. readback from the chip) in the result box and click "BackCalc" and it will work out the options that value would select. It is initially set to "6" as this is the most common default setting for a chip straight from the manufacturer. As with any changing of CV's, it is recommended that you readback the initial value of CV29 before attempting to change things.
( I have withdrawn the "Windows Gadget" version of the CV29 calculator as Microsoft are withdrawing support for Gadgets from operating systems. It may re-appear as an App at some point in the future )
CV's 33-46 or Function Mapping
This is another area of confusion, and a number of decoder makers have their own extensions to the NMRA basic standard mapping which means much more complex options are possible (eg. Zimo, ESU), or additional features are overlayed (eg. CT). To be honest, this is where I'd give up trying to do things through a DCC command station, and get a computer interface and JMRI/DecoderPro. However, if stuck doing things the hard way....
Arnold Huebsch has written a rather decent calculator for these CV's, so rather than me re-write it, here is a link which opens his calculator in a new window. The vertical column are the CV values and handset function buttons, starting with "lights in forward direction/F0" at the top. The horizontal are the output wires on the decoder chip, right hand side being the first (lights) output (usually white wire).