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Microcontroller Programming » Can I use the USB-Serial Programming cable to Program 3.3V Device?

January 18, 2017
by tommytwoeyes
tommytwoeyes's Avatar

I've recently acquired a new Nordic radio device from Sparkfun which seems really cool. I'm eager to work with it, but I realized today it operates and can only be programmed at 3.3V. Kicking myself for not checking this first, I checked my supplies but do not have an FTDI USB-Serial device, like the one Sparkfun recommends for programming this thing.

I do have my NerdKit USB-Serial programming cable, which I believe works based on a PL2303 USB-Serial converter IC embedded in the cable (if I'm not mistaken).

Is it possible to use the NerdKit USB-Serial cable to program 3.3V devices? Is there any reason Sparkfun would say in their user guide for this device that an FTDI programmer is needed (other than their obvious need to promote their own products)? I've done a fair bit of google research, but I've found some sites/blogs/forums in which people say FTDI/PL2303 programmers are virtually interchangeable, while others say they're not, or rather, "it depends."

Their are several different variants of PL2303 chips Prolific makes, and I see some of them appear to operate at 3.3V, but I've been unable to determine which chip is embedded in the USB-Serial cable that came with my NerdKit (I'm unwilling to cut it open because I don't want to damage it).


Can I safely use the NerdKit cable to program a 3.3V device? Are there any caveats? I can power the device separately if needed.

This is the device I need to program:

January 20, 2017
by Rick_S
Rick_S's Avatar

I can't speak for your serial interface you got from NK, but the one I got is 5V not 3.3 and could not be used on a 3.3V device. You don't have to have an FTDI USB/Serial cable specifically, but you would need to verify that whichever chipset the serial cable you get is 3.3V or you would need to go through a level conversion circuit to drop the I/O to 3.3V. Reading the Datasheet, it states that the max for I/O is 3.6V so a 5V adapter would cause damage. Don't forget, this device requires 3.3V power as well and will not play well with other periferals that are 5V.


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