Hello all, Well, the KE7X KRC2 app note is yet another unfinished project I need to get back on.
The KRC2 is a great little decoder box with tremendous flexibility in how you use it but it does require you to carefully study the schematic. Here are some of my more-or-less random observations. I hope to put these into a more cohesive form one of these days (soon). KRC2 Outputs: The KRC2 outputs can be used in high-side driver applications (where the external device needs + voltage) or low-side drivers (where the external device needs a signal pulled to ground). The KRC2 can do both simultaneously. Note that the high-side driver supplies +12 V when asserted but is NOT pulled to ground when it is not asserted. Similarly, the low-side drivers are not pulled up when not asserted. There are 16 high-side and 16 low-side outputs. You can map them anyway you like (even to do a BCD output) but note that the mapping will be the same on the high-side and the low-side. Although there isn't a native BCD coded output, you can make one by using the low-side drivers and supplying the needed pull-up in your external device (which is the way those devices should be designed anyway, but that's another story). Using the AUXBUS: As others have mentioned, the best way to use the KRC2 with the K3 is to use the AUXBUS output on the K3's ACC connector. A caveat is, like the KAT500, the KRC2 must be powered-up before the K3. If it isn't, the K3 will just sit there with a blank screen when you turn it on. That's very scary when it happens to you the first time! The reason that happens is that the KRC2 seems to load the AUXBUS down when it (the KRC2) is not powered-up. I'm not sure I understand why. Bottom line: Turn the KRC2 on first and keep it power-up. Using the Serial Port: Be very careful if you go this route. The problem is that the KRC2 was designed to use the K2's serial port, which if you recall, is a non-standard RS232 interface. If you connect the KRC2 to a standard serial port with the standard RS232 signals RI, CTS, RTS, DSR, and DTR, AND with the KRC2's jumpers W11-W15 connected you could (and probably will) damage the KRC2. Don't ask me how I know that. When jumpers W9, W10 and W22 are installed, the KRC2 can pass K3 serial data on to a PC, for logging or other operating. If you want to do that, the K3's serial data must be 19.2 Kbaud. I haven't played with this mode enough to see how the P3's baud rate fits into the whole scheme. Using the BCD Input: The K3 does put out BCD band data on the ACC jack and this can be used with the KRC2. I don't see problems with this approach other than the known problems associated with the K3's internal pull-ups that limit the loading it can drive on the BCD outputs. I think the KRC2 will work OK but you might not want to have other loads from other decoders on these signals. I have yet to play with this mode. Jack Brindle is a great and friendly resource for questions on the KRC2. I'll get back onto this writing project one of these days as it gets warmer in MT and I take refuge in the coolness of my basement shack. 73 and cheers, Fred KE7X Fred Cady "The Elecraft K3: Design, Configuration and Operation 2nd Edition" "The Elecraft KX3 - Going for the Summit" www.ke7x.com Also available at www.lulu.com (possible discount code JULYBOOKS13) fcady at ieee dot org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
