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

[Don Wilhelm]

Brian,

The schematics for the KX3 is not yet available.  However, I believe the 
KX3 CAT interface is the same as that used in the XG3 signal generator 
(if not exactly the same, it is similar).  You can download the XG3 
manual and find the schematic at the back.
The CAT interface should tolerate the full RS-232 voltage swing, but 
should respond to positive going levels greater than 3 volts and the 
output level will swing up to 9 volts (but does not go negative).

73,
Don W3FPR

On 9/25/2012 10:09 AM, Brian Lodahl OZ2BRN wrote:
> 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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