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Topic: The 0.1uF capacitors when using FTDI programmer (Read 3 times) previous topic - next topic

Vincent19

Quote
The capacitor is there to turn the RTS signal into a pulse, so that when the computer brings RTS low, it briefly pulls reset low, and then the pull-up resistor charges the capacitor again, bringing reset high again.

Source : http://www.gammon.com.au/forum/?id=11637

Can anyone tell me about this ? I do not understand why it needs so. And is DTR =RTS ? My FTDI programmer are using VCC, RXD, TXD, DTR,CTS and GND pins

Thanks !

retrolefty


Quote
The capacitor is there to turn the RTS signal into a pulse, so that when the computer brings RTS low, it briefly pulls reset low, and then the pull-up resistor charges the capacitor again, bringing reset high again.

Source : http://www.gammon.com.au/forum/?id=11637

Can anyone tell me about this ? I do not understand why it needs so. And is DTR =RTS ? My FTDI programmer are using VCC, RXD, TXD, DTR,CTS and GND pins

Thanks !


Why do you need to use DTR or RTS (yes you can use either but not both) ?

When you press upload on the Arduino IDE to upload a new sketch to an attached arduino board, the IDE needs to reset the attached arduino board so the bootloader on the board will start and communicate with the IDE to allow uploading the new sketch.

Lefty

Vincent19

Why not ? My ftdi programmer have the DTR pins and I am required yo connect it to reset pins via 0.1uF cap..but I do not know why

Grumpy_Mike


Why not ? My ftdi programmer have the DTR pins and I am required yo connect it to reset pins via 0.1uF cap..but I do not know why

Your ftdi programmer connects to the reset pin. With serial you have no connection to the reset so the designers of the arduino decided to use the handshaking pin as a reset, rather clever I thought.

Nick Gammon

RTS goes low, as shown here:



However we don't want reset to stay low, so the capacitor turns it into a pulse. Then 10K resistor then charges the cap back up and it becomes high, allowing the processor to run.

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