Altos ACS 8000-15A

On Sun, Jun 14, 2015 at 3:47 PM, Chris Osborn <fozztexx at fozztexx.com> wrote: I wouldn't assume anything with serial ports, especially vintage ones. Look into getting a "traffic light" that displays state on LEDs either in red or red/green (depending on how old/expensive the traffic light - I have both kinds). The "easy" way to sniff out a connection with one is to plug the traffic light into only one side of your connection and see which lines are active, then unplug that and plug it only into the other side and see which lines are active. If you have your null-modem/no-null-modem swaps right, the active lines will be complementary on each side. If, say, RxD is active on both, you'll need a null modem. When you have it right, you should see lights blink when one side or the other is trying to talk. Choosing a baud rate slower than 9600 bps makes it easier to see. Also, some hardware needs hardware flow control present and working. Newer stuff is fast enough that mostly, people just do 3-wire serial (RxD, TxD, and GND), but stuff from the 1970s is expecting CTS and RTS and all that to do the proper things. Sometimes, you can just wire up the computer side to always have CTS active and things will work fine since the computer/terminal side can keep up and doesn't have to throttle one character at a time. Frequently, this requirement can be enabled/disabled with jumpers or software settings on the computer side, but if not, you might need a custom console cable. This is part of the joy of serial comms. If you aren't used to debugging line speeds and parity bits and null-padding chars and hardware handshake lines, it can get very frustrating when you try to connect two devices and they won't talk. By the mid-90s, when most serial comms were relegated to various types of modems, many of the earlier limitations were no longer important, but the further back you go, the more parameters you had to get right before traffic flowed. -ethan