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My mega usb/serial adapter died some time ago, so I bought an external FTDI programer wich I got working on 1.0.1 IDE. I can load any program to the mega, even complex led matrix driver I wrote myself so the ATmega works fine and the external FTDI board does too. Strangely enough I if I want to update the IDE (tried once on 1.0.5 and yesterday downloaded 1.6.5) I get an

 avrdude: stk500v2_getsync(): timeout communicating with programmer

When this problem occurs, I see that the programmer board recieves something (it has Rx and Tx LED's) the Mega resets but never sends any data back, which does happen on 1.0.1 IDE. This happens on my pc, and on a laptop son no pc related problems. I'd keep using this version but now I got an OLED display I want to drive (SSD1306 from waveshare) but I can't compile u8glib on 1.0.1 but I can on 1.6.5, however I can't get a simple blink example to upload with this IDE.

I suspect the DTR pin (reset pin) is handled differently and that makes the mega stay resetting until it times out. What can be the problem here? How can I get more info from the console to solve this?

  • How have you wired your FTDI board? – Majenko Oct 4 '15 at 9:51
  • Do you mean if the programmer is correctly wired to the Mega? Yes, it is. Since it can upload sketches to it on the 1.0.1 IDE – rMaero Oct 5 '15 at 19:32
  • No, I didn't ask you if you thought it was wired correctly. I asked you to tell me how it is wired. Never assume it's correct just because it's been working. Something is wrong, so let's start with that. – Majenko Oct 5 '15 at 20:00
  • Good point. I don't have it in front of me right now so I'll tell you as I remember. Also note that a few hours ago I re – rMaero Oct 5 '15 at 21:17
  • (Pressed enter by mistake) Good point. I don't have it in front of me right now so I'll tell you as I remember. The FTDI chip provides 5V, GND, Rx, Tx, DTR and CTS pins. 5V and GND are connected to the power rails of the Mega (powering it with an external wall-wart PS changes nothing). Rx and Tx are conected crossed to the Rx0 and Tx0 port on the Mega. And finally the DTR is connected to Reset pin on the Mega. CTS is not connected. I believe it is connected correctly and running both versions of the IDE side by side one does upload and the other doesn't. By the way, thank you for your help! – rMaero Oct 5 '15 at 21:29
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You need to add a 100nF (0.1µF) capacitor between DTR and RESET so it generates a pulse instead of a constant LOW all the time the port is open.

The older IDE uses an older version of avrdude. The newer version of avrdude with the newer IDE has extra code for manually manipulating DTR to get around some issues with new versions of the FTDI drivers.

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