Can anyone tell me what the voltages are on the RB2011’s serial port?
I.e. are they ‘proper RS232’ voltages of +3 to +25 volts and -3 to -25 volts or are they ‘serial TTL’ with a swing from 0 to 5 volts?
could always use a voltage tester. On the spec page it says RS232 usually. I would say it uses the most common setting.
Yes, I will put a meter on it but that doesn’t necessarily tell everything.
I’m just trying to work out why I’m having trouble interfacing with a PC COM port, I’m pretty sure I have the connections right and I’m seeing some effect but characters are getting corrupted and only going in one direction.
I’m pretty sure they are official RS232 level.
If you see garbage then your serial speed is probably incorrect.
I have set the speed the same both ends, I’ve tried both 115200 and 9600. I never see anything at the PC end. At the RB2011 end I see maybe 50% characters correct at 115200 - that is I type in the terminal on the PC and about half the time the character appears correctly at the RB2011.
So either I have serious amounts of noise on the connection (it’s not a long cable, just a metre or so) or the two ends are using different logic levels.
I’m away at the moment, when I get home tomorrow I’ll check with a meter, and if I get desperate I’ll get the 'scope out.
I once had similar symptoms, and discovered it was just a bad serial cable. If I applied force (I can’t remember in which direction) to the plug on the RouterBoard end of the cable, the random yet frequent transmission drops and errors cleared right up. Must have been a loose connection/bad solder joint or crimp job. I tossed the cable; problem solved.
– Nathan