[SOLVED] Sparkfun FT232RL board driver issues

Hallo I am building a standalone Arduino, following a combination of these two tutorials: http://www.arduino.cc/en/Main/Standalone and Julian Ilett's "1-Day Project" on youtube

The main difference being that Julian's dispenses with the reset button, due to the soft-reset function of the Sparkfun FTDI Basic board. The driver version from the FTDI site is

I'm using an ATmega368-PU with Uno bootloader. Yesterday, I successfully built and programmed a standalone, with the DTR pin connected to the reset pin on the ATmega via a 100nf cap, and to VCC via 10K Ohm resistor. No hard reset was required and I uploaded several different sketches to the ATmega.

Using a second duplicate FTDI board (and ATmega) I tried to repeat the build and that's where everything went sour. My OS (Win 7 64-bit) refuses to let go of the COM port assigned to the first FTDI board. I cannot communicate with either of the ATmega328's now. In the Arduino IDE, the Serial Port option is greyed out, even with either FTDI board plugged in. When I unplug it, it's still there in my Device Manager. My own Mega2560 is working okay, and shows up (and disappears) from the Device Manager as expected, but I cannot get rid of "USB Serial Port". The only solution so far, is to restart my whole system, at which point the IDE shows the Serial Port again.

I strongly suspect the FTDI driver to be at fault here, and I'm asking if anyone has either had such an issue before, or if you can suggest a fix.


. . . I should probably add that the red TX light on the FTDI board flashes three times during upload attempts, then pulses slowly upon each subsequent attempt to communicate, the RX light doesn't flash at all

avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x02 avrdude: stk500_recv(): programmer is not responding


I hope you realise the USB ports are only enumerated in the IDE as it starts - if you remove a USB serial device, it is removed from the IDE list and not reinstated until you close and re-start the IDE.

{Unless they perhaps fixed this foul-up in later versions?}

Oh yes, of course I'm aware of that. If I unplug the board, then restart the IDE, the serial port is missing, until I reboot my OS. Still, the issue of now being unable to upload any sketches persists. When I plug the board in (after a reboot) the last sketch I put on the chip still runs ok, I just can't communicate with it. I really believe the problem is a combination of the soft reset function on these FTDI boards, and their associated drivers.


You suggested you had connected the DTR line to the 10k resistor. Obviously it should be the ATmega328 reset line on that side of the capacitor that has the 10k pullup.

Yep, exactly as I have it.

In Julian's demo video, he uses CH340G USB-Serial boards; gonna give those a shot. Any online references to troubleshooting the boards I have suggest a wide variety of possible hardware solutions - holding the reset button and counting to 3, connecting the DTR pin directly to the reset pin on the chip, connecting to VCC, not connecting to VCC . . . .

As a last attempt, I'll try re-burning the bootloader onto the chips, but, as I say, I strongly suspect their drivers are f*cked up.

I had to use a 1.0 uF capacitor for the reset function on my stand-alone Arduino board. Also, I am using a FT-232 adapter that I got from DigiKey. I am now able to upload sketches to my board and have had no further problems as far as hardware. Software is another matter - I am not a programmer !!!

Hi is that one (1) microfarad? Thanks for the tip I'll try that too. What's frustrating me most is that I had it working, tried a duplicate FTDI board and then everything f**ked up.

Yeah, Brendan. That is a 1.0 uF cap. I tried with a 0.1 uF and the downloads were too erratic. The cap I used was a monolithic type, but other non-electrolytic types should also work.


0.1uF (or a 0.22) works, I haven't tried a 1.0uF yet; the issue was the latest version of the drivers for this chip/board. I removed them and performed a manual install of the ftdibus.inf and ftdiport.inf files contained in the previous version of the CDM drivers (2.08.30). Now I can upload sketches with a soft reset, read sensors, and hot-swap FTDI boards without issue, each presenting a unique COM port number.


I also had issues with my ftdi board and having to manually reset my atmega chip to successfully load sketches. The dtr pin on my ftdi board stays normal high until right before it uploads the sketch then goes low. To rectify this I wired a tip122 transistor with dtr from ftdi board to in, ground to tip122 and out on the tip to the reset pin of the atmega. The tip122 inverts the signal from the dtr pin on the ftdi chip. So right before it writes the sketch it goes high instead of low. It writes every time now no manual reset required. Currently using Ubuntu 14.04, arduino IDE 1.0.5, and most current ftdi drivers from there website.


I think most people just use the 0.1uF cap method. That way, the sketch will run on the Arduino when it is powered from the USB cable and Serial Monitor is not open. On the reset pin, 10K pullup resistor and 0.1uF cap to DTR. This converts the DTR low signal from the FTDI to a brief pulse low. That is how all the factory made ATmega328P-type Arduinos work.

mrpost33: The tip122 inverts the signal from the dtr pin on the ftdi chip. So right before it writes the sketch it goes high instead of low.

Can't see that that will be useful at all. When you close the port, it will hold the Arduino in reset.