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I'm trying develop my own Arduino. I'm using the ft232rl chip so I can program it over USB. Am pretty sure the chip was working before I connected the ft232rl chip.

My AVR seems to have blown because there's on oscillation on the Xtal pins. Just a straight line. I noticed there's a 1k resistor on the txd and rxd pins. Is that because the chip operates at a different logic level or what?

It's not a cable it's an actually self soldered rt232rl on a breakout board. It's 5V for the system voltage. Am using ATmega328P enter image description here

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    \$\begingroup\$ What AVR chip are you using? What is the system voltage? Some of the FTDI cables are for +5VDC systems some for +3.3VDC. \$\endgroup\$ – mjh2007 Jul 7 '11 at 19:41
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    \$\begingroup\$ Note that the scope probes may be enough to lock up the crystal. Also post a schematic of the circuit. Be sure to check everything one more time to be sure that it works and all components are correctly connected and are there. I for example once forgot to connect ground pin on an ATmega 162 and it worked fine until I set it to use external crystal and connected the MAX232. Then it mysteriously stopped working until I soldered the gorund wire. \$\endgroup\$ – AndrejaKo Jul 7 '11 at 21:15
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    \$\begingroup\$ The schematic is too small to read. \$\endgroup\$ – Mike L. Jul 8 '11 at 10:04
  • \$\begingroup\$ @MikeL: Right click, view image...The picture is fine, just the forum is resizing it too small to read. \$\endgroup\$ – Faken Nov 5 '11 at 17:40
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If the atmega is socketed, you could pull it out, put it on a breaboard and use another arduino as an ISP programmer (see http://arduino.cc/en/Tutorial/ArduinoToBreadboard ) to load a sketch that blinks an LED (or even almost all of the GPIOs and says something repeatedly on the serial transmit pin.

You could do this with the fuses set either for internal oscillator or for the crystal - there are merits to both.

With a USB port theoretically providing only 5v, and that circuit intending to give the atmega 5v supply, especially with the 1k resistors in there it's extremely unlikely that the ft232rl damaged the atmega.

Most likely something is not right in the assembly of the circuit and it will work when that is corrected. Second most likely is a wrong fuse setting on the atmega. Actual damage would be third - and more likely from ESD or bumping wrong wires together while working on it than anything the ft232rl could have done to it.

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I'd start checking whether the FTDI works as expected. The resistor between the FTDI and AVR limits the maximum current, if this AVR port-pin is set to output when the FTDI also tries to send data to the AVR.

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