I've been running some version of BCD breakout combined with my Flex radios for a decade. I used parallel ports, and a USB to parallel converter with DDUTIL, and recently I used a USB-8 relay device to switch +5v onto the 4 lines needed to communicate with my amp and antenna switch. Flex has added a dedicated means to get band data out of the radio to control external devices. The cable is made by FTDI and is $26 from Mouser The cable plugs into the USB port on the back of a 6XXX radio. Added to the software is a new "USB cables" field under settings.
More than one cable can be added and they give CAT, BIT, BCD, LPDA and DSTAR hardware data choices to allow control by the radio to peripheral hardware devices. My amp is a ALS-1300 and it allows remote band-switching using Yaesu BCD code. Years ago I modified a MFJ RCS-4 antenna switch to automatically bandswitch to Yaesu BCD as well, using a Unified Microsystems BCD-10 (now replaced with a BCD-14. The BCD-14 can control up to 13 bands of antenna from 160M-70cm, using Yaesu BCD. So my choice of cable is the above C232HM cable, but other choices exist depending on need.
As is shown there are 5 bits to the BCD code. Normally there re 4 bits but the field has been expanded to allow for VHF/UHF/SHF transverter choices to be accommodated, so you can control virtually any device probably up through light by judicious programming of the cable. I'm only interest in HF programming so I set things up for that. The reason I include the expanded coverage is to point out how powerful this device is. Note also 60M is represented as 00000 for a band choice. I use this in my scheme to automatically switch in the antenna in my stable of antennas that loads best on 60M. It turns out my amp does not recognize 00000 so the amp does not transmit when 60M is chosen. How convenient is that?
Included here is a breakout board I built including parts listed. The board is wired such that a standard CAT5 cable can be inserted between the RJ-45 and the ARI-500/ALS-1300. LED's were included to easily troubleshoot any issues. I later added a Unified Microsystems BCD-14 to run my antenna switch
My latest antenna system uses a inv-L for 160, a vertical wire for 80, a 1/4 wave vert for 40 and a 18 foot wire parallel with the 40M. The 160M antenna also tunes 60M with SWR less than 1.6:1, and the 80M also tunes 30M with a SWR of 2.5:1, and the 40/20 combo tunes 40M with 1.2:1, 20M with SWR 1.8:1, 17M with SWR 2.1:1, 15M with SWR1.25:1, 12M with SWR 1.9:1 and 10M with SWR 1:9:1. 10 bands auto-switched! I have a MFJ 998 auto tuner for touch-up tuning.
Here is a pic of the finished breakout box with breakout for both amp and antenna switch. The switching is very fast, easily fast enough for SO2R
This new cable from Flex is highly recommended if you're interested in automating your station.