[Elecraft] K3/P3 TXD tap

[K4PI]

I used serial data with my K3S/P3/Steppir/HF Amp set up for a long time 
by using Y cables to get data to all of them. So finally decided to 
change over to USB 100% which I did but now using the CBLP3Y cable on 
the K3S/P3 combo I am still going to need some kind of Y connection 
again to tap off of RXD/TXD.  I am looking at making a Y cable to 
install between the P3 PC DE9P connector to pick up RXD or TXD from it 
and let the amp monitor that.  I know you can buy cables and even 
circuit boxes to do this but I wanted to build this one myself as I 
built the one Steppir used and it worked great.   If you want to see 
what Steppir does, S13 cable, see the link below.

www.steppir.com/wp-content/uploads/2011/10/Y-Cable.pdf

If anyone has done this home brew I would like to know how you did it, 
ie which connector on the P3 and which pins.  I need more than just band 
data provided by the ACC plug for the amp and Steppir.  Too bad there is 
not a RXD/TXD tap in the K3 ACC plug or a tap plug in the P3.  I guess 
one could be installed in the P3 blank slots and tap over to the RXD/TXD 
connectors,  73 Mike K4PI