Hi there
Unruh wrote:
> Yes, well... The RS232 standard says that teh signal levels are -12V and
> +12V and that the absolute minimum be -5V and +5V. However, many serial
> chip makers have bent those standards and the serial port may or may not
> respond to the 0,5 level that the PPS output actually delivers. There is
> absolutely no reason why it should. That signal is completely out of spec.
> If yours does work, it is because your serial port manufacturer severely
> bent the rules. But many (most?) do. But it could well be that the serial
> port is flakey on especially the 0V instead of -5 to -12 V end.
In V24 it's -25 ... 25 V [1]. -3 ... 3 V isn't defined.
Most level translators however are completely happy with 'TTL' [2]
signals. This is not bending the specs, it's within the specs. Not being
happy with 'TTL' is also within the specs.
If you want to make sure have a look at the data sheets of your level
translators. Most consider < 0.8 V low and > 2 V high.
> The parallel port specs state that the signal levels are 0V and 5 V which
> is exactly what the garmin delivers.
An alternative is converting the Garmin signals to RS232.
[1] Most level translators can cope with -15 ... 15 V
[2] TTL high is actually Ca 3.5 V. CMOS high is 5 V (when supplied
with 5 V power).
Regards,
Rob
--
Anglo-Saxon management is a memetic virus
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