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Topic: Capacitor on DTR pin? (Read 8088 times) previous topic - next topic

artswan

I am using the FTDI Basic Breakout (5.0V) from Sparkfun to program my standalone 168 Arduino. When I run a hookup wire from the FTDI Basic Breakout board DTR pin to the Reset pin on the Arduino and then try to program the chip, it doesn't work. HOWEVER, when I put a disc capacitor (0.1uf, 0.001 uf, 0.47 uf, or anything similar) from the DTR pin to the Reset pin on the chip instead of the wire, everything programs wonderfully and the auto-reset works, etc. All the photos I have ever seen on the hookup show a wire. Why does it take the capacitor to make it work instead?

Grumpy_Mike

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Why does it take the capacitor to make it work instead?

Because the level on this signal line changes when the serial bridge is connected (enabled in software). However on the reset you only want a pulse. The capacitor acts as a differentiator.

artswan

Thanks! That helps. But, why do all the examples, ads, etc. show a wire? Is this common or something with my hookup? Am I doing something wrong?

retrolefty

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Thanks! That helps. But, why do all the examples, ads, etc. show a wire? Is this common or something with my hookup? Am I doing something wrong?


All the Arduino (and clones) board schmatics I have seen used a cap to connect the DTR from the FTDI to the arduino reset. Can you post a link to the examples you are speaking of?

Lefty


artswan

Yes. While waiting for a reply, I went off and searched some schematics and some other posts on standalone arduino specifically and found several that showed the inline cap.

So, I am wondering,... thinking about getting the Ardweeny kit sold by Solarbotics, etc. The photos show the programming pins on top where you plug in the FTDI adapter for programming. Haven't seen the schematics yet... so I am wondering if the cap is already built into the circuit, or I will have to add it in somehow?

retrolefty

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Haven't seen the schematics yet


Can't say for sure without the schematic but I would think that they would include to series cap if they expect the Arduino IDE and the on-board Arduino bootloader software to work correctly for downloading new sketches.

Lefty

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