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Topic: Series resistor for IC-to-IC interface (Read 749 times) previous topic - next topic

kesh

Hi. First time poster, waiting for his Nano to arrive in a few days!

I need some help on basic understanding on IC-to-IC interface. I'm more of a software person and not much on (practical) circuit design. (My circuit design experience goes all the way back to the undergrad EE microprocessor class some umpteen years ago.)

I've been studying Arduino Nano schematic and see that there are 1k-Ohm resistors on the TX and RX lines between ATmega MCU and FT232RL. Are these resistors necessary? Or would it be possible to have these pins connected directly without resistors? And could someone enlighten me on the reason behind these series resistors?

I'm planning on connecting Noritake VFD module with CMOS async serial interface either to the Nano or to another FT232 chip, and figuring out whether I need to have the series resistors for it or not.

TIA,
Kesh

RuggedCircuits

Quote
I've been studying Arduino Nano schematic and see that there are 1k-Ohm resistors on the TX and RX lines between ATmega MCU and FT232RL. Are these resistors necessary? Or would it be possible to have these pins connected directly without resistors? And could someone enlighten me on the reason behind these series resistors?


They are both optional and necessary :)   Optional because no, they are not truly required. Necessary because people tend to want to communicate with other devices over serial. So you have the situation where two devices are both trying to drive the same signal, and that can burn out the devices if one drives high and the other drives low. With a resistor in series, the current is limited if one tries to drive high and the other tries to drive low, so the devices are protected.

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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

kesh

Thanks, Rug'd. That makes sense. - kesh

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