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Need advice on troubleshooting APC Smart-Ups

I'm having an issue reading from an older model APC Smart-UPS. Here's what works and what doesn't...

** Mac w/Serial-to-USB Cable **
Using an APC 940-0024C serial cable, I can connect the APC to a Mac using a Serial-to-USB, open up a terminal at 2400 baud and type a single 'Y' character, which results in the proper response of 'SM<cr>'. I'm not sure what the Mac is using other than the baudrate, but I'm guessing it is 8N1. I'm using SCREEN to open the device at 2400.

** NI **
When I connect this same serial cable to an NI's rs232 serial port, and issue a 'Y' the response is 'S' instead of 'SM<cr>'. It appears that whenever I send a letter, the APC sends back a different letter. So 'YQR' sends back 'SW+' instead of a longer verbose string.

The port is configured as:
Send_Command dvUPS,'SET BAUD 2400,N,8,1';
Send_Command dvUPS,'HSOFF';
Send_Command dvUPS,'CHARDM-255';

The strange thing is that I can issue APC commands to shutdown and the commands work from the NI, but with a garbled response.

** NXI **
I tried making my own cable from another AMX APC post, running the wires to an NXI's rs232's Ground, Receive, and Transmit. This curiously sent the characters to the APC (and worked) but never appeared to receive anything from the APC –*the LED never lit up on response on the NXI.

In summary...

Using APC 940-0024C...
Mac using Serial-to-USB at 2400 sends and receives perfectly
NI using a Serial port sends correctly (triggers shutdown and demo mode 'A') but receives garbled response
NXI using rs232 phoenix connector to Ground, Receive, Transmit, directly to APC pins 9,1,2 sends correctly but doesn't receive any response

Does anyone know what I might be missing? Why does this cable work perfectly on a Mac/PC but not from the NI or NXI?

Comments

  • DHawthorneDHawthorne Posts: 4,584
    AMX serial ports use a bunch of pins for RS-422 and 485 that RS-232 only devices use for handshaking. Also, as I recall, APC at one time used a special pinout of their own. Best solution is to look up the pins and make your cable to order.
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