From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2002-01-14 19:29:37
Hi Jim,
> Unless I read it wrong, the max rate of the DS275 is 19 KBaud
> and it still needs a power source larger than +5 volts
> ( a 9 volt battery )?
Say what? No, DS275 can operate on 5V only. It has a voltage
doubler inside to generate the higher RS232 voltages. I have
one running on 5V so I know it works. The data sheet says
that pin Vcc is for +5V (min 4.5 typ 5.0 max 5.5V). The data
sheet mentions that a 9V battery can be added to the DRV pin
for higher voltage, but I don't think we need that. I have a
uC connected to PC (RS232) with DS275, no problems at all, 5V
only operation. The reason that I suggested DS275 in the
first place was because it was low power, possibly low enough
to get power from the PC serial port. Regarding baud rate,
there is no mention of max baud rate in the data sheet, they
show a circuit for a handheld RS232 device connected via
stereo mini-jack that was tested at 19.2k baud. The data
sheet does not say this is the maximum rate. I have a few
DS275s here. I will try to test at higher baud rates and
let you folks know. What baud rate are we shooting for? I
keep hearing 115.2k mentioned, but do we need that? Why is
that rate picked, because it's the max for most PC serial
ports? I really don't think we need 115.2k.
-- Doug
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