I'm making my own USB to serial breakout board and I used the FTDI Friend board as a reference, but I don't understand the purpose of the TX and RTSDTR line 10ohm resistors.
I know for a fact that they are completely useless because I have an FTDI breakout board which works without them, but I'd like to know why the FTDI Friend has them, stability? noise reduction?
The FTDI chip datasheet doesn't say a word about them.
The 100 ohm resistors provide a bit of protection should the lines be connected incorrectly.
Solenoid:
I know for a fact that they are completely useless because
Just because something appears to work, doesn't mean it is robust and works in all cases. Those components are not completely useless.
The protection resistors aren't mentioned in a datasheet because they aren't necessary in all applications. Something like the FTDI Friend was designed for prototyping and other non-static applications. So additional protection was added for that design.
[quote author=James C4S link=topic=148061.msg1112615#msg1112615 date=1360513103]
Solenoid:
I know for a fact that they are completely useless because
Just because something appears to work, doesn't mean it is robust and works in all cases. Those components are not completely useless.
The protection resistors aren't mentioned in a datasheet because they aren't necessary in all applications. Something like the FTDI Friend was designed for prototyping and other non-static applications. So additional protection was added for that design.
[/quote]Very well then. The DTR, RTS and TX are all outputs so I assume low impedance and therefore if wrongly connected it will probably fry. I didn't think of this scenario.
