From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ross Boylan Subject: Serial port shuts down APC UPS Date: Thu, 23 Jan 2003 17:39:02 -0800 Sender: linux-serial-owner@vger.kernel.org Message-ID: <20030124013902.GF765@wheat.boylan.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org Cc: Ross Boylan When I connect my APC BackUPS 650 to ttyS1 the unit turns off when Linux starts up. APC tells me (after several days) that a different cable is necessary for Unixy systems than for windows. Apparently some voltage on the serial port gets transmitted back to the unit, which interprets it as a shut down signal. (That is, I continue to get power, but if the wall power fails the battery won't kick in). Since the hardware works under Windows, I assume there is a software solution, and I would like to find it. APC further says the port should be at 2400 baud, with Flow set to XON/XOFF (which might also be known as no FIFO). I find baud control but no flow control in setserial, and at any rate my understanding is that it doesn't reprogram the physical device. serial.c appears to set FIFO on, so that's probably part of the problem. Is it safe to turn it off, or would that require rearchitecting things? (Also, I don't know how to turn it off). As a final complication, I get "LSR safety check engaged" on ttyS1 when I start, even if the cable is disconnected. My suspicion is that this indicates I have the wrong IO range or IRQ in setserial. I've built my kernel from source (2.4.19 under Debian), so it would be relatively easy for me to modify serial.c (for example)--if I knew what to do! Gigabyte GI-7IXE4 motherboard, using the AMD 751/756 chipset. Athlon processor. I've looked around for the ports in /proc/isapnp and lspci, but haven't found anything. A mouse is on the other port, and I have an internal modem using another port. Also using USB scanner. There are quite a lot of peripherals; interrupts are in short supply. In case you can't tell, I'm no hardware expert. I'd appreciate any help. What do I need to do to get the serial port to work with my UPS? Thanks. P.S. I just subscribed to the list. I'd appreciate it if you cc'd me in case the subscription hasn't taken yet.