potter
Member
Registered: Feb 2000
Location: SW Virginia
Posts: 290 |
quote:
Originally posted by Trinition:
They say it will generate the proper RS-232 voltage levels (5V I believe).
If I remember correctly, RS-232 signals are between -5 and -12 (or was it 24) is low and between +5 and +12 is high. For TTL between 0 and +0.7 is low, and between +3 and +5 is high.
quote:
But wouldn't that reguire a power source?
There are two different techniques that they could be using: 1 powering the circuit off of one (or more) or the signal lines, and 2 using a charge pump. The Handspring serial cradle uses both of these, powering its self off of one of the control lines coming from the host computer.
quote:
MarkSpace says they get the +5V from the Visor. Where? Can anyone find the pin that give 5V?
There is no out right 5V coming from the Visor. Maybe one can get some power out of the USB port (would not think so). Or since when at rest as TXD line is high, one could get power there (though this would be error prone, since heavy serial out would invalidate this assumption). I would think it more likely to pull the power from RS-232 device, similar to the Handspring Serial Cradle. But, I would hope, improved, but pulling power from any of the lines driven by the RS-232 device.
quote:
What would be MarkSpace's return policy?
Do not know. Cannot comment.
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07-17-2000 05:20 PM
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