I bought a Roostick from here, I believe this uses the FTDI chip. Most recently I bought an Arduino parts kit to learn about the Arduino board here. One of the ways this board can be programmed is using an FTDI cable available here.

I believe the Roostick and the FTDI cable use the same chip for the USB to UART conversion. The Roostick has a breakout pins for Gnd, R_DD, R_TXD, R_RXD and 15.6V. My question is, if I could use the roostick to program the Ardunio directly in my Breadboard kit. I am guessing I would have to hook up the Gnds together and swap the R_TXD and R_RXD between the Rootstick and the Ardunio. but the 15.6 Volts on the roostick bother me.

If I hook this up, would this fry my chip?


According to the product page/schematic, there is no 15.6V generated on the Roostick itself. It would normally come from the Roomba battery, but if you are using the roostick on it's own it won't be present.
So providing you have nothing else capable of providing >5V actually attached to the Roostick when you use it with the Arduino you won't fry your chip.

The FT232 is set to 3.3V logic level output, but you may not need any level conversion if your Arduino is running from 5V. I think the FT232 can handle inputs up to Vcc (which is at 5V from the USB) and the 3.3V high level should be fine for your Arduino input.
You can play safe in case the FT232R doesn't like an input voltage higher than it's VCCIO setting by putting a resistive voltage divider (to divide the 5V to 3.3V) on the line.
I'd just try it and see, if it doesn't work too well there are plenty of level shift ICs out there (and google knows plenty about simple discrete transistor type solutions too)

Of course if your Arduino runs from 3.3V(?) this is irrelevant.
Check the FT232R datasheet for more details I only glanced briefly.

No power connection is necessary since both the Roostick and Arduino have their own power source. So, you would just connect the Roostick/Arduino grounds together, and the serial lines: The pads on the Roostick are marked:R_TX, R_RX, and GND

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  • \$\begingroup\$ Thanks for that Oli, I went ahead and connected it anyway. My Arduino is running off 9V battery. I believe the 7805 regulator drops it to 5V(?). Nothing fried, but doesn't seem to be actually doing the programming. In the Arduino IDE, I get a "avrdude: stk500_getsync(): not in sync: resp=0x00" error. I swapped the R_TX and R_RX around, to no avail. I am trying to compare the two scematics dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Roomba/… and sparkfun.com/datasheets/DevTools/FTDI%20Cable%205V.pdf \$\endgroup\$ – Chaitanya Jan 29 '12 at 8:16
  • \$\begingroup\$ Yes, your arduino will regulate the 9V to 5V or 3.3V for the chips on board. I've never used Arduino though so I can't help on the programming side. Looking at the schematics, the main differences are: The FTDI cable uses 5V for it's IOs (see connection to VCCIO from Vbus) The RTS, CTS lines are used and there are 10k pullups on the lines. No idea of the details but looking at that I doubt it will work without some hacking of the Roostick - you should probably look/ask in the Arduino forums for details of how the programming works. \$\endgroup\$ – Oli Glaser Jan 29 '12 at 8:53

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