View Full Version : What are the two capacitors for between the BS2 and the PC Serial port?

01-12-2006, 11:57 AM

in the schematic on how to connect the BS2p to the serial port of a computer, it shows that there are two 0.1uf caps before pin3 and pin4 of the BS2. I was just wondering what's the use of these caps, and what would happen if i wanted to connect a serial cable directly to the BS2, without the caps. (i haven't tried it yet, but it's very tempting since i dont have any caps laying around :P)

Thanks again

Chris Savage
01-12-2006, 12:16 PM
This was just covered a few threads down. See my post in the following thread.


Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

01-12-2006, 09:08 PM
In short -- they decouple the 'reset' DTR signal, so if some application (like Hyperterm) holds it 'active', the BS2 can still run. Without them, Hyperterm holds the BS2 in reset.

So, as long as you disconnect the DTR line, or don't want to reset your BS2, or control the DTR line in your own code, you can leave the capacitors off.

01-13-2006, 05:09 AM
Thanks, didnt notice the other thread.