FT232RL: USB to Serial 232 TTL Adapter –?and ISP?

I’m now the owner of this little device:


It works great for the Serial part so far –?but now I wonder, how I can make use of these ISP pins.

I tried connecting this:

But in the IDE I get the error:

avrdude: stk500_getsync(): not in sync: resp=0x00
when using AVR ISP as a programmer


avrdude: usbdev_open(): did not find any USB device "usb"
when using AVRIPS mkII as a programmer

I’m beginning to wonder: are those yellow ISP pins meant for programming the Arduino via ISP from USB or are they meant for ‘converting ’ ISP signals to Serial 232? So, are they inputs or outputs?

Can anyone make a guess?

Dont !!
Those pins are for communication with the MCU on the adapter board.
..Yes it can be reprogrammed, but get the knowhow first
In Arduino IDE : select the correct arduino mini.
Press reset-button on the mini as upload starts...
Cables to connect: RX, TX, Ucc and GND
(remember Tx on one unit to RX on the other)

That is not designed for ISP programming, it's for programming using the bootloader. As such you connect it to Rxd and Txd plus reset and GND. Also it doesn't appear to have the reset cap on DTR so you would have to add that.


Thanks, but your answers confuse me a little?…

So what you’re saying is:
No, these yellow ISP pins are no outputs to connect to an Arduino and program it.
These yellow ISP pins are inputs and they are meant for programming the FTDI chip on the adapter itself.

Is that right?

Well, if so, can you point me to where in the datasheet it sais, that the FT232RL has a (re-)programming capability via ISP? To me, it doesn’t look like that at all?…

Sorry Darkwing, I didn't spot that yellow connector. I have no idea what that's for, the FT232 cannot be programmed, it can be made to bit-bash several of its IO pins and maybe they are connected to that 2x3 header. In which case it might be possible to ISP an Arduino with it, but I can't find any supporting documentation.

So in lieu of any documentation (typical of these BS cheap vendors) I would have to say you cannot use that connector.


If the yellow pins are connected to FT232 such as here
you can bit-bang a bootloader in.

See if the pins connect to the FT232 as they do on a duemilanove.

Thanks for your answers!

In the meantime I found a little something; it sais translated:

As a new feature there is a 6-pin ISP header available. With it, avrdude and avrftdi you can program Atmels and Arduino bootloaders. A special version of avrdude with compiled FTDI driver is neccessary.

And then the following link is given: http://helix.air.net.au/index.php/avrdude-and-ftdi-232h/

That’s information from some kind of official supplier. Sounds like interesting material, I’ll see if I can try this out the next couple of days. I keep you posted!

EDIT: Even more official, but also even more confusing:


Can anyone make sense of the naming for the connections?


Those are the names of the IO functions the pins perform. See the duemilanove schematic for X3, and see where they connect to in the link I posted.

Are those signal names right? If so it's not ISP/SPI in the normal sense of the term, not even close despite the label.

That said the signals do match the old X3 header, was that used for a bit-banged SPI on the Duemilanove?


Yes, see first link in reply #5. My Duemilanove board still has pins in X3 for that, you connect jumpers from X3 to the ICSP header for bootloading.

how to interface 2 ft232rl devices

I know this is an old thread, but I picked up one of these exact "Inland" branded ftdi usb adapter with the isp header. It did not have any information, and took a bit of research to get it working right.

Looks like this works for the ISP header and avrdude (at least on Linux):

 id    = "inland";
 desc  = "FT232R Synchronous BitBang";
 type  = "ftdi_syncbb";
 connection_type = usb;
 reset = 7; # 
 sck   = 5; # 
 mosi  = 6; # 
 miso  = 3; #

Just thought this might help others...

also, I noted that trying to burn bootloader was flakey as erase seemed to fail in avrdude (although it appears to have actually succeeded on the chip).

I was getting this with avrdude 6.1

avrdude: Device signature = 0x1e950f
avrdude: safemode: lfuse reads as FF
avrdude: safemode: hfuse reads as DA
avrdude: safemode: efuse reads as 5
avrdude: erasing chip
avrdude: Program enable command not successful. Retrying.
avrdude: Program enable command not successful. Retrying.
avrdude: Program enable command not successful. Retrying.
avrdude: Program enable command not successful. Retrying.
avrdude: Device is not responding to program enable. Check connection.

I found that latest avrdude-6.3 doesn't seem to have this issue any longer and seems to work fine... I have replaced the avrdude (6.0.1) in my arduino-1.6.7 folder with 6.3 and it seems to be quite happy.

Hardly worth the effort though, considering the low cost of a USBASP.

I got one of these a month ago, as a Serial bit-banger for the ESP8266-01. (the one with the SM DIP FTDI chip). Word Of Warning! the 3V/5V switch only change4s the voltage of the serial I/O & handshake lines. it does NOT change the VCC voltage. the VCC pin will still be +5V, no matter which position the switch is. If you plan on running anything off the VCC pin, at 3V, You will need to add a regulator (I.E. L78L33AC) between the project & the adaptor. Word of the wise, before you fry, Check the voltage!

FT232 only outputs 50mA at 3.3V, so not a great power source for much. Especially not ESP8266.

Dear CrossRoads,
Just today I found out that I've bought the exact same Deek Robot as shown in your picture. As far as I could tell, there is no documentation, so maybe you can point me in the right direction. There is a switch to change 5V to 3.3V for TTL. I switched it, but I'm no sure how to verify that it works and what I need to change in the configuration of the pins in order to connect to my project. Especially pin 5 on the Sonoff Board. (Note. I'm not an engineer). Pin 3 on the FTDI still gives 5V on my multimeter... What am I overlooking?

FTDI (Deek Robot) Sonoff switch (Basis Wifi Smart Switch)
(1) GND (1)
(2) CTS (2) GND
(3) 5V (3) RX
(4) TXD (4) TX
(5) RXD (5) 3V3
(6) DTR

Link to Sonoff:http://sonoff.itead.cc/en/products/sonoff/sonoff-basic

I just bought a FT232 (FTDI) cable from Microcenter in USA and when I switch from 5V to 3.3V, I don't see the pin 3 (from the left from top view) as 3.3V. It is still 5V! What is the problem with this Inland adapter? Anybody figured out how to obtain 3.3V at the output?

The switch only controls the IO levels of the signal lines, not the 5V supply line.

How can I power (or program) a 3.3V Arduino with this FTDI board then? How can I obtain 3.3V at the pin output that power the Arduino? I don't want to burn an arduino using 3.3V as Vcc.

At the back of Inland FT232 Adapter box, it says:
"The switch on the adapter allows configuring the board for 5V or 3.3V operation to match the power limitations of an Arduino compatible board..."
What I understand from this sentence is, it should give 3.3V at the output. Is there any way to connect a 3.3V arduino to computer using this Inland FT232 (FTDI) adapter?