USB to serial issue/question

Hi,

Is anyone familiar with the ARD-FTDI FTDI Serial Adapter 5V / 3.3V?
I bought it for programming arduino mini pro 3.3 and esp8266.

The trouble is that with the switch on 3.3, the Vcc still outputs 5V.
I guess I can use a converter to get it down to 3.3.

But the Rx and TX pins are showing 3.4-3.5V. Is that too high?

Thanks

The trouble is that with the switch on 3.3, the Vcc still outputs 5V. I guess I can use a converter to get it down to 3.3.

Yup, that’s the way those boards work. The switch only changes the voltage on the FT232 VCCIO pin, the header supply pin is connected the usb +5.

Solution? Just use three wires to connect, using the 3v3 supply of target. You have to in most cases since the FT232 3v3 regulator is only good for 50ma of output and it isn’t available on any pin from the looks of that board.

Yeah, maybe you can solder a flying lead onto the 3v3 side of the switch and cut the +5V trace at the pin and jumper it over... but you still only have 50ma.

There is no problem powering the Pro Mini 3.3 V at 5 V. In that case, the 3.3 V only means that the board can run at 3.3 V (which the 16 MHz Pro Mini can not do reliably). Of course, you might have other parts in your circuit that can't handle 5 V, I can't know whether that is the case.

With the ESP8266, you definitely can't power it at 5 V.

sorimaki: But the Rx and TX pins are showing 3.4-3.5V. Is that too high?

It should be fine for the Pro Mini and ESP8266 both. It's quite common for people to use even 5 V logic levels with the ESP8266, and apparently the CEO of the manufacturer has said this is supported.

One approach would be to use a 1117-series reg (you can solder through-hole caps to the legs of the reg in TO-220 to save space)....

Re 5v voltage levels on ESP8266 - they don't have the protection diodes like most microcontrollers have - they've got a different pin protection scheme.

The black CH340G adapters with the voltage switch, and the green ones with the microusb connector and switch both output 3.3 on the Vcc pin when set to 3.3v - they're like $2 or so on ebay. Just make sure you get the right ones.

Great, thank you for the responses. I'll give it a try and see how it works