[Elecraft] Repost: KX3 ACC1 interface - logic signal levels - what is "official" Elecraft standard for this ?

Brian Lodahl OZ2BRN oz2brn at post.cybercity.dk
Tue Sep 25 10:09:19 EDT 2012


Hi,

I'm reposting this because I'm still struggling to get my customized CAT 
+ CW interface for the Kx3 to work:

I attempted yesterday to wire up a TTL Serial cable from FTDI, containg 
both CAT as well CW keying (using #RTS), and I can easily get the CW to 
work (keying using #RTS through a 4N25 and two 1N5711 diodes for dit and 
dah), but it seems that the CAT does not work with this interface.

My question again: -What is the "official" Elecraft electrical 
specifications for the ACC1 interface ??? What voltage levels for Rx and 
Tx, respectively, with respect to GND or Positive voltage ?

-Does anyone have a schematic of the ACC1 interface for Kx3 that I can 
take a look at ?

73'
Brian OZ2BRN




Den 21-Sep-12 08:34, Brian Lodahl OZ2BRN skrev:
> 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)
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