defcon.klaxon
Lifetime Supporting Member
Hey guys, I've been working on a couple of systems that were originally programmed and integrated by another programmer at a different business. At one site, radio problems have been occurring for a couple of years and excuses ranged from interference from PG&E switching stations to some malcontent citizen to marine radios from the nearby lake. After seeing nothing to suggest any of those things with my spectrum analyzer, I suggested we take a look at the RJ45 to DE9 adapter needed to plug the PLC into the radio. Sure enough, it was wired incorrectly! TxD, RxD and GND were ok but the flow control lines were incorrect as follows:
Pin 1 of dsub - should be DCD, was actually RTS
Pin 2 of dsub - should be RxD and was correct
Pin 3 of dsub - should be TxD and was correct
Pin 4 of dsub - should be DTR, was actually CTS
Pin 5 of dsub - should be GND and was correct
Pin 6 of dsub - should be DSR, was actually DTR
Pin 7 of dsub - should be RTS, was actually DCD
Pin 8 of dsub - should be CTS, was actually +5VDC
Pin 9 of dsub - should be RI, was not connected
I'm reading up on the RS-232 flow control protocol, but was wondering if one of you were well versed enough to see what was mismatched here and describe how the radios would work intermittently. It would seem that the data would be transmitted and received only when everything just happened to be "right" on the flow control, but with CTS being injected with +5VDC and thus always being asserted, it seems a miracle it would ever work at all.
Pin 1 of dsub - should be DCD, was actually RTS
Pin 2 of dsub - should be RxD and was correct
Pin 3 of dsub - should be TxD and was correct
Pin 4 of dsub - should be DTR, was actually CTS
Pin 5 of dsub - should be GND and was correct
Pin 6 of dsub - should be DSR, was actually DTR
Pin 7 of dsub - should be RTS, was actually DCD
Pin 8 of dsub - should be CTS, was actually +5VDC
Pin 9 of dsub - should be RI, was not connected
I'm reading up on the RS-232 flow control protocol, but was wondering if one of you were well versed enough to see what was mismatched here and describe how the radios would work intermittently. It would seem that the data would be transmitted and received only when everything just happened to be "right" on the flow control, but with CTS being injected with +5VDC and thus always being asserted, it seems a miracle it would ever work at all.