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James,<br>
<br>
My understanding is that they shift both ways. Regulating the level
back down to TTL is pretty simple - it's the boosting it up that
requires a non-trivial pump. The problem is in raising the usual
TTL levels (from about 3V to 5V) up to the spec for RS232 (about 19V
from memory). Most devices contain the same chip (MAX232 - which is
purpose built for it.) Note that some RS232 devices/interfaces
don't insist on the 19V levels and will work fine with a low voltage
input so you can always try - particularly if the lead is short.)<br>
<br>
USB has different driver circuitry again.<br>
<br>
Mike<br>
<br>
On 03/01/15 16:35, jwmartnet . wrote:
<blockquote
cite="mid:CAPLoHypuKWOfrSPQH=JXCCx2YFV3jaJYpzJ_1yj3tq=eGbbRHQ@mail.gmail.com"
type="cite">
<p dir="ltr">Hi,</p>
<p dir="ltr">I want to connect a serial console to my device but
need a bit of advice before purchasing components.</p>
<p dir="ltr">According to the article linked below, I need a '
3.3V TTL to RS-232 level shifter'</p>
<p dir="ltr"><a moz-do-not-send="true"
href="http://www.cyrius.com/debian/kirkwood/qnap/ts-219/serial/">http://www.cyrius.com/debian/kirkwood/qnap/ts-219/serial/</a></p>
<p dir="ltr">Do these converters work bidirectional? Or does it
specifically need to be 3.3V TTL to RS-232 and not RS232 to 3.3v
TTL?</p>
<p dir="ltr">Anything to avoid?</p>
<p dir="ltr">Probably wishful thinking, but.. I guess TTL to USB
wouldn't work without intervening electronics?</p>
<p dir="ltr">Cheers<br>
James <br>
</p>
<br>
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