Hi Kx3 users, Other posts have previously dealt with the issue that the standard KXUSB cable for Kx3 does not support CW keying from the computer to the Kx3 radio, simply from the fact that as opposed to the ordinary serial connection (old RS-232 standard), the RTS and CTS pins are not available in the 3.5 mm, three-pin TRS jack connector for ACC1 in the Kx3.
Pursuing this further, and not wanting to have more than one USB cable to my PC from my Kx3 for all of my buisness on the PC side, I want now to build a new interface cable using a custom cable assembly from FTDI: http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm Then using either RTS or CTS flags in my PC's radio interface setup (log program Win-Test) to pull the CW key connection in the Kx3, possibly via a FET or Opto Coupler. - I have a 4N25 in mind for this ... with parallel coupling of two 1N5711 to the paddle dit's and dah's. I did the very same thing on my K2, and it worked like a charm. Checking the signal levels on my oscilloscope today on the ACC1 data connection, I find: Tip connection = Rx data from the computer to the Kx3 = 5,0 - 5,2 volts level (generated by the FTDI line driver) Ring connection = Tx data to the computer from the Kx3 = 7,0-7,5 volts level (generated by the Kx3 line driver) both with respect to GND being the sleeve pin of the ACC1 jack plug, and looking pretty, noise-free and free of any transients. Good, nice square signals with good integrity. Baud rate of the data here is obviously configurable, and with your PC's logging program so is the polling rate of how often the PC requests data from the Kx3. My question :What is the "official" Elecraft electrical specifications for the ACC1 interface ??? What voltage levels for Rx and Tx, respectively, and what impedance to I terminate with when I interface with e.g. opto coupler for my project ? Would I be OK assuming I just use a 5-volt TTL-level cable version here, both ways Rx+Tx OK ? TTL-232R-5V: http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf 73' Brian OZ2BRN Kx3 # 1118, K2 # 6936 (to which I did the same mod) ______________________________________________________________ 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
