Arduino RS232/TTL shifter programming

Hi group,

i have a little problem with downloading from the IDE to optiboot (UNO) chip. Because of the nature of my project, I use the chip only (in my hardware) and a custom-made RS232/TTL converter. I added the "auto reset" circuitry, too (DTR to serial cap and a pullup of 10k).

For now, when I try to upload a sketch, I got a message "avrdude out of sync". The Pin13 led flashes correctly (3x, boot loader), when I loop back the TXD and RXD pins (at the level converter), I can "see myself" in a terminal program at the PC.

The oscilloscope shows a correct TTL serial data on TXD/RXD pins, the reset waveform at the RES pin looks good, too ...

But I can not download the binary object from IDE to chip ... When I hook up to the same wires (GND, RES, TXD, RXD) an empty Arduino UNO board and send there a compiled sketch, using the board's usbserial coverter, everything is okay.

Any idea? Thanks in forward.

Two days of searching ... thus .. NEVER TRUST THE "PASSIVE" (couple of transistors) LEVEL CONVERTERS!

The level converter I used was something like http://www.pvelectronic.eu/hlavni-odd/podle-kategorii/rs232-ttl-uart/rs232-shifter-smd.html, see the schematics http://www.sparkfun.com/datasheets/Prototyping/RS232-Shifter-SMD.pdf. Don't trust that piece of ...

At lower speed, or at higher speed/low data volumes it works okay ... but for a data transfer, needed to burn a sketch thru emulated stk programmer (UNO uses 115200bps), it produces some, but only very rare, bit-errors - and you're out of sync.

A simple PL2323 board, robbed from an old mobile phone cord, fixed the problem definitely.

Solved.