Matty B T
Posts: 2
Joined: Wed Apr 25, 2018 5:47 pm

Need to convert USB to UART

Wed Apr 25, 2018 6:06 pm

Hi All,

Very new here, and very new to raspberry pi, so apologies if this is a dumb question, and double apologies if it's in the wrong place.

I need more UART ports because I need to interface with a handful of external bluetooth modules, similar to an HC-05

I've done a bit of research, and it seems like the best option for me is converting USBs into UARTs, as opposed to the other options, like bit-banging, which seem more advanced than my level.

Most of the posts talk about FTDI, which I found here: https://www.sparkfun.com/products/9718

However, I also found another product, which to me looks similar in function, here: https://www.sparkfun.com/products/12977

Would the second one work as well? I can't tell the second one is actually FTDI, so maybe I'd be sacrificing reliability and signal quality? Also the FTDI one offers 5V and 3.3V, whereas I think this one only offers 3.3V.... I am having a little trouble deciding which voltage I need.

The reviews on the second one are mostly people who needed to communicate with a UART port on a Pi/Arduino. I need to convert the Pi's USB port into a UART port.... though I guess those are probably the same. Based on HC-05 pinouts, I think either 3.3V or 5V would work, but I am unsure about any other differences between the two options that may make one more suited for my needs

Any help would be greatly appreciated!

User avatar
topguy
Posts: 6719
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: Need to convert USB to UART

Wed Apr 25, 2018 11:53 pm

The cables are basically the same with slightly different packaging. But the 5V or 3.3V part is important.

The cables can both be used to connect a device to the Pi, but also connect the GPIO UART on the Pi to a PC. ( But you should not use the 5V cable on the GPIO pins because they are 3.3V. )

If the devices you are going to use can handle both 3.3V and 5V then you could use any cable. Also note that some of the cables has 5V on the VCC pin but still use 3.3V for RX an TX.

FTDI are one brand of usb2serial chips, another is Prolific which created the very common PL2303 chip, unless you get some counterfeit ones they usually work very well on the Pi and under Linux.

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