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Hi,
I have constructed a 'minimalist' UNO-type Arduino.
There is a '328 chip + bootloader + 16MHz Xtal& 22pF caps.( I have checked everything by substituting it in an Arduino board,
successfully bending a load of pins as well )
The reset pin is connected to 5V by a 10K resistor with a push-sw to short it to ground.
The Rx and Tx go via a MAX232 to a 9-pin connector and I am using a USB to RS232 cable to upload Arduino sketches.
Initially, I couldnt get any joy because the cable was a Mickey-Mouse job.
To my astonishment, the 'contact' email in China actually returned my emails and gave me a link to
to a working driver!
Not only that, but I managed to do my homework and successfully did a loop-back test to check the
 cable worked as advertised!
 I checked the baud-rate was correct, but the sketches uploads always failed with that standard error message:
 "avrdude skt500 sync error resp 0X00". It was a 'reset' problem after all.
I finally tracked down some old forum discussions and it transpires that you have to press the manual reset
at the right time, but no-one is quite sure what that time is, although it may be between zero and 10 seconds.
I do love mathematical precision, dont you?
Is there any way to accomplish this automatically? Does the cable not send some signal down the DTR line?
The CP210X module has a DTR signal like that, does anyone happen to know if the cables have a similar fucntion?

bruce
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Málaga, Spain
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Press the reset and hold it till the sketch is about to start downloading. At that moment, release the reset button.

You will need to enable the verbose mode in the Arduino IDE section and you will see when it starts to download.

Not mathematical but a bit more empirical smiley-wink
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Denmark
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Is there any way to accomplish this automatically?

You can make an auto-reset by connecting the DTR line through a 100nF capacitor to reset on your Arduino.

Try a forum search on CP210X, it has been discussed several times
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You have a one second window in which to release reset.  Use verbose compile and reset at abou the point that the sketch size is reported.  Alternately, recompile the bootloader with a longer tImeout.
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Hello guys and thanks for the replies.
I tried the 'verbose' trick and it seems to work.
I dont understand how to reload the bootloader with a longer timeout.
Erni, I fear you misunderstood my post: I'm not using a CP210X module, I'm using a UB to RS232 cable.
The chip inside is obviously a custom Chinese 'blob-on-board' and theres no data on it, AFAIK.
However, I do wonder if these cables have the facility to reset the micro via the DTR pin,
rather like the CP210X modules do.

bruce
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