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Topic: 1K resistors on TX/RX between FTDI and AVR, what for ? (Read 4506 times) previous topic - next topic

barbatruc

Hello,

   Could someone explain me why there are 1K resistors on serial lines between AVR and FTDI chip ?

   Would the reason have to do with "TTL level", "CMOS level", "RS232 level" ?

   Would that mean that to connect a

   Regards,

   G.

 

Grumpy_Mike

It is to allow you to use pin 0 and pin 1 without the FTDI chip over riding the signal level you put in.

barbatruc

> It is to allow you to use pin 0 and pin 1 without the FTDI chip over riding the signal level you put in.

If I understand your answer, it means that my AVR will be able to use its serial port on the PINs without being disturbed by the powered-on FTDI chip, correct ?

If correct, won't the 1K resistors "lower" the signal between AVR and FTDI when "talking together" ?

Regards,

Grumpy_Mike

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without being disturbed by the powered-on FTDI chip

Yes, well it allows your signals to over ride them.

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won't the 1K resistors "lower" the signal between AVR and FTDI

A series resistor by itself does not lower a signal, for that you need a potential divider.
So 1K as the top of a potential divider with the input impedance of an arduino pin as the bottom leg changes the signal lever only a very little, it's no worth bothering about.

barbatruc


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