I just got a Prodigy Express and an Atlas H15/16-44 loco with decoder. I have begun to learn how to program the decoder, but I am confused about programming CVs where they have bits as well. For example, for my decoder CV51 controls the front headlight outputs. Then under CV51 there are several different bits that make the front headlight function as a mars light, gyro, strobe, etc… How do you program the bits with a Prodigy Express? Can anyone help me?
I’m not familiar at all with the Prodigy Express, but there are 8 Bits to one Byte, with values doubling as you count from right to left, beginning with 1; i.e., 1, 2, 4, 8, 16, 32, 64, 128. To set a Byte to a particular value, you add the values of each Bit that you want to set within that Byte. CV 29 is the most common Byte that requires the setting of individual Bits to configure a decoder. Most DCC systems automatically compute the value for CV 29, but sometimes it may be necessary to set them manually when the automatic configuration fails for whatever reason.
Smitty,
Check your Prodigy Express owner’s manual. It should tell you in there. I have the NCE Power Cab and it does mention in the manual how to change the individual bit(s) under a particular CV. It’s a little involved but not too difficult.
Tom
I can try.
Basically, the variable you want has several options. Rather than publish a huge table with all the options, they simply tell you to set the bits as follows.
So you want the features that need bits 1, 2, and 3 set to “one”. This gives you a binary number of 111, which is decimal 7. (4+2+1=7). So you press the “7” key, and whatever key you press to enter that value in the CV.
You might have a lot of options for one feature, and have 8 bits to enter. So you end up with a number like 1100 1011, which is hexadecimal 0xCB. Easier to enter, but the math can be harder… So you enter the decimal value, 203.
With 8 bits, you have up to 1111 1111 (0xFF) or 255 possible values. Entering binary isn’t too hard, and hex is even easier. It’s the math that trips us up. We can handle decimal numbers a lot better.
The instructions for the system should explain how to enter the values into the decoder. The tricky part is converting 1111 to 15.
The simple way is to write the bits on a piece of paper and add them up to get the value you want. Write exactly as they show in the manual, with bit zero being the rightmost bit.
Then add them up. From left to right, the values are:
128+64+32+16+8+4+2+1. If the bit value is zero, add zero for that position.
One of the recent issues of MR (iirc) had an article that helped explained programming CV’s that used multiple bits. Hex and binary can be confusing at first, but once you get it, it makes sense.
The above explainations are pretty good. Howstuffworks.com has a good article that will help explain it all too.
Your Computer’s Calculator in scientific mode should reveal Hex and Binary values.
Enter a value 0 to 255 under DEC value and then select BIN for binary to get a corresponding value in bit form.