odd FTDI problem

[knuckles]

hi
i have aquired a FTDI board (silab CP2102 on board ) off chinabay and hooked it up to a sparkfun pro micro 328 and a Xino Uno clone and everything is fine when programming examples
typically i connect Tx ,Rx ,5V and Grd ,and DTR via a cap to reset on the board .
so far so good ...

now, when i use this setup on a genuine UNO it does not work at all.
any ideas why it wont work ?

[knuckles]

i saw a reference to a pull up 10k resistor to 5v after the cap ,wonder if that will do it ?

[knuckles]

i tried a sparkfun FTDI basic board to load on sketches  but still its the same .it will load onto a pro micro or Xino clone but it wont load a sketch onto a UNO . (2 UNO boards have been tried)
thats using Rx to Tx ,Tx to Rx ,V and Grd and DTR via a cap to reset .

[knuckles]

i tried a 10k pull up resistor after the cap but still no loading of a sketch

[CrossRoads]

Why are you connecting a USB/Serial adapter to a board that already has one installed (uno)? What is it you're trying to do?

CP2102 board is not an FTDI board - FTDI board will have an FT232RL chip, like the older Duemilanove boards.

[knuckles]

i was under the impression that i could use the Rx Tx and V and Grnd with reset  to load a sketch on any arduino or clone with a suitable FTDI board ,but if its the case that if it has a USB device already on board then it wont work it seems .

[CrossRoads]

You keep saying FTDI board, that is not what you have.  You have a CP2102 based module which uses totally different drivers.
The pin labeled Reset on that module is not used, that is the reset input to the CP2102. What you  can is cut the trace going to that header pin, and connect the pin to the DTR pad on the module if it has one.

I suspect the CP2102 could be connected as you describe; you may have to put the onboard ATmega16U2 into reset using its reset pin (on the other 2x3 header area near the Aref/SCL/SDA header pins).

[knuckles]

err i was using a Sparkfun FTDI basic so i am using a FTDI .

[CrossRoads]

Technically, that should work - you may have to put the onboard USB/Serial adapter into Reset to make sure it is not interfering with the Rx/Tx lines.
I've not tried external programming when internal programming was available.  Seems an odd thing to do.

[knuckles]

i guess it looks so ,but i am trying to get down to the 'nuts and bolts' of boards of varying types to get understanding

[CrossRoads]

Have you looked over the Products page?
I think for each board type it shows whether a USB interface is supported on board, or if an external USB/Serial adapter is needed.
If building your own design, you can decide whether to add one in or not
(using a MIKROE483 for example
http://www.mouser.com/ProductDetail/mikroElektronika/MIKROE-483/?qs=%2fha2pyFadugsEwyLV5fFyIWdPbushEDhRSvnBE0ODG8%3d
or glomming an e-bay module on somehow,
or if making a PCB, using a discrete USB/Serial chip and the support components)