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Author Topic: Uno Rev 3 and J2  (Read 725 times)
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South Africa
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Hello all

My first post, please be gentle lol. Help im just starting in electronics as a hobby, just bought an Uno Rev3, looking at the board i see 4 points one marked J2, What is this for and the other 2 for.
just a simple answer and or why they are there would be great, will delve in deeper as my experence grows

Thanx in advance


Please see attached pic.


* ArduinoUno_R3_J2.jpg (248.85 KB, 652x465 - viewed 17 times.)
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See http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf
JP2 is in the center and allows you access to the 16U2 port PB4..PB7

Which does not answer the "Why" question ...
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South Africa
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Thanx it was nagging me why its there and marked and couldnt find any info on it, the Why not a biggy, sure i could find somre thing on that somewhere, any idea what the othe two pad are for just above it?

Thanx for the answer
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Thanx it was nagging me why its there and marked and couldnt find any info on it, the Why not a biggy, sure i could find somre thing on that somewhere, any idea what the othe two pad are for just above it?

Thanx for the answer

JP2 is the 4 "pads."  They are actually holes for header pins to be inserted but they just filled the holes with solder.  I believe it was for an upcoming feature which never happened...
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Look at the schematic pdf: JP2 is 4 signals: 16U2 port PB4..PB7
BTW: the 6pin header block above is obviously the one labelled ICSP2 in the schematic, can be used to program the 16U2
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Cool thanx for the answers maybe do some investigating, for future use or something

early days for me so just getting as much info as i can.

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They are not really intended to be filled with solder, its just that the automatic PCB production process addeds solder paste to all the pads indiscriminantly - you have to solder-suck them out to add a header if you actually want to use them (which most people won't)
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Part of tha board construction involved a wave soldering machine... for all the thru hole parts and that's when those holes were filled in. There are too many for any hand soldering.

Bob
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Thanx Bob, You learn something new every day, if in the future i start to use that future at least i know what they are for and how to use them
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Part of tha board construction involved a wave soldering machine... for all the thru hole parts and that's when those holes were filled in. There are too many for any hand soldering.

Bob
Have they never heard of peelable solder mask?

And if I had designed the board with those pads, they would have been there so that you could implement RTS, CTS, and other modem handshaking signals, in the USB interface firmware.

The old FT232 chips they used to use provided them, but I don't know if they had them broken out into pads or not.
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Nope going to do some research on it

not sure about the usb not there yet lol
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