When using an FTDI header with a bare ATMega chip, I know that I need to connect DTR via a capacitor to RESET. My question is: when using a polarized capacitor, where does the negative side go? Connected to the DTR pin or the RESET pin?
Also, assuming that this goes "before" the resistor to (+) that the RESET line is always connected to?
Thanks!
osmosis311:
When using an FTDI header with a bare ATMega chip, I know that I need to connect DTR via a capacitor to RESET. My question is: when using a polarised capacitor, where does the negative side go? Connected to the DTR pin or the RESET pin?
The DTR pin.
osmosis311:
Also, assuming that this goes "before" the resistor to (+) that the RESET line is always connected to?
Of course.
A non-polarized ceramaic 0.1uF (100nF), 16V or 25V or 50V rated, is all that is needed tho. Available for a few cents.
+5 - 10K pullup resistor - reset pin
DTR from FTDI - 0.1uF cap - reset pin
On my home built Arduino compatible controller, I had to increase the value of that cap to 1.0 uF. I used a 50 v monolithic cap and have not had a single problem uploading sketches to it since. Just a little info to hopefully save you some time and frustration when trying to upload your sketches !!
Did you have a 10K pullup resistor or something else?
I've only ever used 10K and 0.1uF, no issues.
Thanks Robert! Based on your suggestion I ordered these today:
Ok, a bit overkill. I can see the 22pF and 100nF being used a lot, and the rest hardly ever unless you are doing some analog circuit work.
I bought a bunch of these
http://www.dipmicro.com/store/C1K22-50
and these
http://www.dipmicro.com/store/C5K10-50
and that's all I end up using with thruhole digital designs.
10uF and 1uF aluminum electrolytics (polarized) also if I have regulators.