On Fri Jun 5 9:55 , Cesar Bonilla sent: >Jed Clear escribió: >> On Thu Jun 4 10:58 , Cesar Bonilla <[email protected]> sent: >>> I have a Net5501 with a USB Memory. I connect to Console port but I >>>can't see anything! >>> [snip] >>> >>Are you using a null modem cable (pins 2 and 3 crossed)? >> >>Also it might be worth giving 9600 a shot, in case it's not quite factory >>fresh. > >I found many diferent types of cable:
Most of these will work in many cases. >Null modem without handshaking >2 - 3 >3 - 2 >5 - 5 The first one is the bare minimum (Tx, Rx, Ground) with the key feature of the pin 2-3 crosses. This works if both devices ignore their hardware flow control inputs, which is often the default. For 9600 and 19200, you can generally get away w/o flow control. >Null modem with loop back handshaking >2 - 3 >3 - 2 >5 - 5 >1 + 4 + 6 - NONE >NONE - 1 + 4 + 6 >7 + 8 - NONE >NONE - 7 + 8 This one should work, but the local loopbacks only "cheat" the hardware handshaking and provide no flow control. You could get overrun errors at the upper speeds (e.g. 115,200). >Null modem with partial handshaking >1 - 7 + 8 >2 - 3 >3 - 2 >4 - 6 >5 - 5 >6 - 4 >7 + 8 - 1 I'm very suspicious of this one. Generally you want DCD (1) to be driven by DTR (4), not RTS (7), if at all. Who ever came up with this probably had hardware flow control disabled anyway. >Null modem with full handshaking >2 - 3 >3 - 2 >4 - 6 >5 - 5 >6 - 4 >7 - 8 >8 - 7 This should work the best for most cases. >I'm confusing. Can you say me what pins connect to other side? Welcome to the confusing world of cheating on the RS-232 "standard". The standard was designed to let data terminal equipment (DTE), such as a dumb terminal or server (and now a PC), talk to data communications equipment (DCE, i.e. a modem). Almost immediately people began using the RS-232 ports on two pieces of DTE to direct connect without modems. So they had to figure out how to get around the handshaking designed to talk to a modem. Since many ways will work in various cases, you get many solutions. If you're the curious type, and want to fully grok what's going on, you can find out more starting here http://en.wikipedia.org/wiki/Flow_control and here http://en.wikipedia.org/wiki/RS_232#Conventions. If you just want to build a cable and move on, go with the last configuration. However, my personal favorite is: 2 - 3 3 - 2 5 - 5 4 - 6 + 1 6 + 1 - 4 7 - 8 8 - 7 But in practice I haven't picked up a soldering iron in ages. I just keep around a handful of DE9 gender bender and null modem inserts. -Jed, Grey Beard Hardware Engineer _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
