View Full Version : USB to Serial NPN transistor
01-26-2009, 01:21 AM
On the USB to serial converter an NPN transistor is used to drive the RESn line to a low state but nowhere does it say what transistor is it. Does anyone know?
Almost any general-purpose NPN should do, like a 2N3904.
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01-26-2009, 01:54 AM
01-26-2009, 03:43 AM
query: what USB to serial converter?!?
is there a circuit out that uses discrete components to convert USB to serial and where can
i find the schematic for it?
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Phil Pilgrim (PhiPi)
01-26-2009, 04:30 AM
None with discrete components. All of them use an IC converter chip, such as the FT232R.
01-26-2009, 08:21 AM
I use an P2N2222 - just be careful to get the correct pinout (the older 2N2222 used a different pinout).
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01-26-2009, 08:34 AM
Has anybody tried using MProg to invert the polarity of the DTR signal?· It seems like it should work, but I didn't try it because Parallax didn't do it...
Phil Pilgrim (PhiPi)
01-26-2009, 09:21 AM
Yes, and apparently it works. Read about it here (http://forums.parallax.com/showthread.php?p=766645).
01-26-2009, 10:49 AM
Has anybody tried using MProg to invert the polarity of the DTR signal? It seems like it should work, but I didn't try it because Parallax didn't do it...
I do it also on 2 self made PropPlugs - works well.
I have a 10nF capacitor between the inverted DTR and the RES pin.
Maybe Parallax don't do it, because it's cheaper to add a resistor and transistor, than program each unit with MPROG (or they just not had the idea?)