SOLVED:DTR conflict?

Development Tools IDE 1.x
1

I am using a USB to TTL adapter (like this one http://www.aliexpress.com/item/USB-2-0-to-UART-TTL-6PIN-Connector-Module-Serial-Converter-CP2102-New/32246790758.html?spm=2114.30010308.3.11.vFrUup&ws_ab_test=searchweb201556_9,searchweb201602_2_301_10034_10033_507_10020_10001_10002_10017_10010_10005_10011_10006_10003_10021_10004_10022_10009_10008_10018_10019,searchweb201603_3&btsid=32337067-5538-4aaf-b2d6-18a26a7adc23) with a ProMini328/8mHz.

When following the usual wiring instructions (i.e. 100nF cap between DTR and Arduino reset line) the ProMini can be programmed nicely within the IDE (which I guess means that the auto-reset is properly setup). With all the data that is successfully transferred to/from the device one might be inclined to think that all is well..

But I am then using the same HW configuration when I later communicate with the device by using a Java / jSSC library based PC application. And as long as the above "DTR wire" is in place, the Java based Serial interface access fails miserably (The Arduino does not seem to get any of the data that the PC application is sending) - but as soon as I "cut" the "DTR wire" the Java based Serial communication works perfectly. So I installed a jumper as quick-fix...

Is the above behaviour "normal" - or is it an indication that the wiring is flawed or that one of the used components might be defective?

2

DTR is asserted by most applications when they open the serial port, so this is resetting the Arduino. You need to either tell your program not to assert DTR (if it can be told not to do this) or not connect the DTR wire when you don't want to have autoreset.

(you can also clobber autoreset by putting a 10uf cap (really anything 1uf or higher should work) between the Reset pin and ground)

I put "RST_EN" jumpers on all the boards I make that I put the DTR reset on.

3

Thanks for the explanation.. I had a closer look at jSSC library sources and found an extended version of the SerialPort.setParams(..) API that allows to control the DTR handling. problem solved :slight_smile: