Odd (to me) Serial Problem

Using Arduino IDE 1.x
1

A have a strange problem that I have not seen up till a month or so ago.

When I plug a Dccduino Nano into a usb port, it initializes and the sketch loaded in it runs as it should.

Then I start the Arduino ide (1.6.8) and about halfway through loading, the led13 on the Nano starts blinking quickly at about 0.5 Hz (not the 1 Hz blink rate of the Blink sketch). It will do this till I open the Serial Monitor at which time the Nano goes back to running the sketch that is in it. If I close Serial Monitor, led13 goes back to flashing.

If I start the ide first, then plug in the board, the board initializes and the led13 blinks till I open Serial Monitor at which time the sketch in the attached Nano runs as it should

I have three of these nano boards and they all behave the same no matter the sketch loaded.

System is Windows 10 64 bit.

Any ideas or is this new with ver 1.6.8

Thanks,

Jamie.

2

This is a bug in 1.6.8 on windows, they screwed up serial port handling. It continually opens and closes the serial port, causing the DTR autoreset circuit to continually reset the board, and the fast blink is from the bootloader.

Use an older version (I recommend 1.6.5r5 - 1.6.6 and 1.6.7 have some added bugs), or use the 1.6.9 hourly pre-release build if you're brave.

3

Thanks DrAzzy, I'll try the downgrade route for now.

4

Downgrading to 1.6.5r5 solved the problem. Thanks again.