Question concerning low voltage arduino Pro mini

[dakky]

Hello

i don't understand, how to connect my ftdi programmer to the low power tweaked arduino pro mini

http://www.mysensors.org/battery/ProMiniMod.png

how is the ardiuno powered, while the sketches get uploaded? Or is this only for 5V ftdi programmers? Mine can be jumpered to 3.3V

Thx

[Anticimex]

@dakky You cut out the regulator that provides 3.3V from the RAW pin (which can be a larger voltage). When you have cut the regulator, you are expected to provide a "clean" 3.3V voltage on VCC pin(s) (which the programmer does when programming).

[dakky]

Hurm i thought, vcc ALWAYS has to be a clean voltage, in case of the 3.3V Arduino 3.3V confused
or is it only important not to connect the vcc pin, when using a 5v programmer?

[Anticimex]

@dakky What do you mean? VCC ALWAYS has to be a clean voltage. Also from programmer. You have to use a 3.3V capable programmer (or rather, FTDI interface) when interfacing with a 3.3V Arduino.
If you use a 5V FTDI interface, you will fry the Arduino unless you cut the VCC pin on the programmer header (in which case you have to provide 3.3V on the other VCC pin).

[dakky]

mission accomplished: everbody is confused ^^

ok in my eyes removing the regultator results in one thing: using the RAW pin with more than 3.3V will kill the arduino. but the pin we are talking about is the vcc pin on the ftdi interface (is interface the correct word btw?)
i'm aware, that on (every?) vcc pin on the board the max voltage is 3.3V. but should i not power the vcc from the programmer? When looking on the image above, it says: dont connect the vcc pin. i don't see the reason, because

1. i need some kind of power
2. of course i should put a max of 3.3V on this pin (as always when connecting the vcc pin)

so i don't see any reson why not to use this pin.

That's my problem

[Anticimex]

@dakky If you remove the regulator, RAW pin is useless. The regulator is responsible of regulating the RAW voltage into 3.3V. Remove it, and you will not be able to regulate the RAW voltage (and it will not have a path to VCC either) as you can see here.

When you program the Arduino it has to receive power. I do not know your setup, but you have two options:

1. Supply power from a 3.3V FTDI programming interface
2. Supply power from another source (and make sure a 5V FTDI programming interface does not connect to a VCC pin).

I do not know who made the picture but I would assume that it is for those with an 3.3V Arduino and a 5V FTDI board.

[dakky]

ah now i understand ... and feel a little bit stupid

maybe trying to think too much about simple things .. thanks for your patience

[Anticimex]

@dakky No worries. Better to think too much than too little

[FotoFieber]

The 328P is working with
8 MHz in the range of +2.7 - +5.5 V

I do program all my arduinos with 5V.

Detach the NRF24L01+ and other 3.3V sensors or they may die while you attach 5V.

Use at your own risk.

[Anticimex]

@FotoFieber @dakky yeah, but the cheap Chinese clones on eBay does not because people have reported them dying so make sure you use "genuine" HW in that case. I have not experienced it myself because my ftdi board is 3.3V only and it's only my gw (Arduino nano) that run on 5V and that one has "native" USB so no ftdi board is needed.

[tbowmo]

I think one of the problems, of dying 3V3 arduinos, is people that doesn't disconnect the 3V3 regulator on board. If you then supply the board with 5V on VCC pins, you might destroy the regulator, which then could short circuit.

But if the regulator is removed from the circuit, as in this example, I don't see any thing wrong in supplying the arduino with 5V on the VCC pins, but you should take care of any connected peripherals, that aren't 5V compatible.

[Anticimex]

I see. Perhaps the site should be updated to clarify this. It has a section for FTDI voltage selection. Ping @hek

[hek]

@Anticimex

So what should I update?

When doing FTDI upload for 3v3 Pro Minis, shouldn't the FTDI be set to 3v3?
I would rather not make this page to complex as it is part of the "getting started" guide.

[Anticimex]

@hek Perhaps it is fine as it is. I just thought that since this thread was created in the first plase, there is room for confusion. Especially since the picture linked in the authors first post is from the site.

[dakky]

In this case a simple note on the battery site, that we have to be careful to supply a stable 3v3 source after removing the regulator would help.
For you, as u are much more experienced, this is a nobrainer, but for beginners like me, this remark would help.

[hek]

Ok, added a note over there. Will pop up next time I deploy.