Messages in this thread | | | Date | Tue, 18 Jan 2000 01:09:58 +0000 | From | Thorsten Kranzkowski <> | Subject | Re: Serial Port voltage drops with Linux |
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On Mon, Jan 17, 2000 at 03:07:35PM +0100, Jens Benecke wrote: > Hi, > > The situation is this: When we connect the hardware to the serial port, the > signal amplitude breaks down to lower than +3V (which is miniumum for the > PC to detect a "0"). With DOS, the signal amplitude varies from -10..+10 V > (approx) for 1/0 signals. With Linux, it's -10..<+3V, and that is not > enough.
Umm - Linux doesn't adjust Power supply voltage levels and it doesn't swap new serial line driver IC's in place either :-))
You have made __double__ shure you didn't connect two output lines together (eg. TxD from computer to TxD from your device)? And you also checked your GND connection?
> Do you have any further ideas about this? Why do the ports behave so much > differently (no matter if we start setserial or not) when using Linux? In > theory (yeah, right) it's hardware that should behave the same under any > OS, at least in respect to voltage levels and power consumption?
Yes, they _do_ behave equally :)
> BTW, we tried three different serial port hardware boards (ISA) so the > hardware should not be at fault.
...and have booted DOS on the very same computer with the very same ISA-boards and your device?
How did you build the power supply of your device? An external AC-powersupply ('Netzteil') or from some unused 'to be set to 12V' status lines? If the latter, are they set to 'high level' when you connect your device?
> I have put the QBasic source and the C source at > http://www.pinguin.conetix.de/serial.zip, perhaps someone can shed a little > light on this. There is also a complete DOS floppy boot image including > QBasic and the .bas file for those who do not have a bootable DOS handy > (dos.img.gz). > > Thanks a lot!
Keine Ursache! Thorsten
-- | Thorsten Kranzkowski Internet: dl8bcu@gmx.net | | Mobile: ++49 161 7210230 Snail: Niemannsweg 30, 49201 Dissen, Germany | | Ampr: dl8bcu@db0lj.#rpl.deu.eu, dl8bcu@marvin.dl8bcu.ampr.org [44.130.8.19] |
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