Uploading to Pro Mini fails with FTDI

[gohan]

there is a limit in voltage difference between vcc and GPIO pins, can't remember now exactly but it could be a cause.

[petewill]

@ben999 I think I understand what you're asking. If so, I do it frequently with my projects. What I do is just unplug the VCC DuPont cable from the FTDI adapter. Here is a picture of what I mean.

[ben999]

Hi @petewill

Thanks a lot for your suggestion (nice picture BTW)

This is exactly the way i (used to) do. But sadly it doesn't work anymore. I can only upload sketches with VCC connected and external power source disconnected. (what would be the outcome in case i leave FTDI's Vcc AND external power source connected to Pro Mini?)

So it is for now impossible to get the serial monitor feedback while using the node in real-life condition... :(

[gohan]

Maybe nothing maybe something could get fried. You could still make a SD logger that @sundberg84 published on Openhardware.io

[mfalkvidd]

@petewill I have something that might make things even easier: wouldn't you get the same result by removing the 5/3.3V jumper on the ftdi?
EDIT: No, not a good idea (see discussion below)

[gohan]

That jumper should also set the logic level of the data pins, doesn't it?

[mfalkvidd]

@gohan good point. I guess the best way to figure out is to bring out a multimeter.

[Yveaux]

@gohan said in Uploading to Pro Mini fails with FTDI:

That jumper should also set the logic level of the data pins, doesn't it?

Typically, from my experience, that jumper only sets the logic level of the serial interface. The VCC pin stays at the USB supply level, so around 5V.

Update: Apparently the Sparkfun board does also change the VCC level (ref: https://learn.sparkfun.com/tutorials/serial-basic-hookup-guide)

Conclusion: Better check with your board!

[gohan]

I used it to program my sonoff and it didn't fry it so it also sets vcc to 3.3v

[Yveaux]

@gohan said in Uploading to Pro Mini fails with FTDI:

I used it to program my sonoff and it didn't fry it

That's one way to find out ;-)

I just want to stress there are multiple designs out there (also with FTDI alternatives) and it's better to be safe than sorry.

[mfalkvidd]

I checked my FTDI adapter. The jumper does switch both Vcc and logic levels, so removing the jumper is probably a bad idea.

[gohan]

@yveaux I know, I fried a sonoff with a supposedly "universal" ftdi adapter

[dbemowsk]

I have all my FTDI adapters set to 3.3v. I too use them to flash my sonoff modules, and those WILL fry if you try to flash them with 5v. My pro minis flash just fine at 3.3v.

Some time back before I got my Vera controller I tried using an FTDI adapter for my gateway and could not get the thing to work. Testing it, I found that my TXD line was transmitting, but my RXD was not receiving. Check that you have communication in both directions.

[petewill]

@ben999 Sorry for the delay. Work has been crazy lately. I see there are plenty of answers above and I echo them. I try not to upload with two power sources connected. If everything is 5v you are probably safe but I see you're using batteries and I'd not risk it just to be safe. I have used two power sources in the past but I have since changed my ways. I can't remember what stopped me but I believe I was getting strange results. I don't think I ever fried any hardware but why risk it...? :)

If you are still having this issue have you tried with another Pro Mini and different code? Is anything coming out of the serial monitor or is it just blank?