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Topic: Arduino Pro Mini 3V3 with TTL-232R-3V3 gives 5V (Read 4 times) previous topic - next topic


I use an FTDI TTL-232R-3V3 cable to connect my PC to my Arduino Pro Mini 3V3. Problem that I found was that the cable is not providing 3V3 but 5V on the VCC connection ! So in this combination the Arduino is powered by 5V instead of 3V3 that should be....

Or is it me doing something wrong ? Anyone using the same configuration ?



Some more background information from the Arduino Pro Mini Quickstart Guide :
The board comes without built-in USB circuitry, so an off-board USB-to-TTL serial convertor must be used to upload sketches. This can be a FTDI TTL-232R USB - TTL Level Serial Converter Cable for the 5V Arduino Mini Pro), or a FTDI TTL-232R-3V3 USB - TTL Level Serial Converter Cable or the SparkFun FTDI Basic Breakout Board for a 3.3V Arduino Mini Pro. One convenient way to connect these is by inserting a six-pin 0.1" male pin header into the end of the FTDI cable or breakout board, and pressing it against the six hole programming header on the Mini Pro.


Sep 23, 2009, 08:36 am Last Edit: Sep 23, 2009, 08:38 am by borref Reason: 1
The TTL-232R-3V3 cable is wired for 3V3 signal levels, but it brings out 5V on the VCC line. To use this with a  Pro-Min-3V3,  you should connect VCC (from the cable) to the RAW input on the Pro-Mini-3V3. Power will then pass through the Pro-Mini regulator and supply the required 3V3.

If you connect VCC from FTDI to VCC on the Pro Mini, you run the risk of damaging the FTDI chip embedded in the cable. Your Pro-Mini should not suffer from this, but  you may harm peripheral devices attached to the Pro-Mini that expect 3V3 logic and power.



I've been puzzling over the voltage question also, since I plan to use a TTL-232R 3V3 with a Pro Mini 328 3.3V, so I was glad to find this thread.  Oddly, a few suppliers of the FTDI 3V3 cable indicated the VCC supplies 3.3V instead of 5V, which greatly confused this hardware-challenged programmer.  Would plugging the cable's 6-pin connector directly and cleanly into the Pro Mini (using a 6-pin male pin header) connect it VCC to VCC?  If so, how would I split off the VCC line individually and route it to the Pro Mini's RAW input?  Also, I wonder why SparkFun doesn't carry the TTL-232R 3V3?


Datapoint: I have an FTDI Basic, is marked 3.3V, has worked just fine for lots of programming of 5V Promini's and 3.3v Promini.
Outut measures 3.23V when connected USB port.
Vcc on Promini measures the same with both prominis (but then there there is nothing to take it higher either).

How are you guys getting 5V out of the FTDI? Have you blown the regulator on the FT232RL chip?
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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