USB-TTL CP2102 converter & Attiny series


need help on this tool I've, wrongly?, bought

The advantage of this module with respect to a USB-RS232 converter, is that the data, on the
other side of the interface, have a TTL levels and hence can be directly interfaced with the I / O of
a microcontrollore.

It looks like cannot find anything on the net on how to connect it to program an Attiny45. and via Arduino IDE i got a message USBtiny board not found.

at least I've understand how to connect RST, MOSI, MISO, VCC and GND, but missing, just likein Arduino, the SCK pin.

So do I bought something wrong??

Thanks 4 help m8s

you probably have the wrong type. this is only good if the attiny has a serial bootloader (rx/tx). this is rare. new chips from the factory do not and require isp programmer (miso/mosi/sck) like usbasp. these are cheap on ebay.

Thx John for reply,

so what about if I load the bootloader via Arduino ISP into the ATtiny and then program it via the CP2102, would it work ?

Or, would you pls suggest what I should but to program an ATtuny45 or 85, I'm really lost in this jungle of programmers ;)......


if a serial bootloader is installed in the attiny then cp2102 works. but as i said this is rare because it has small memory and few pins. another more common way to program attiny is vusb type bootloader (ie digispark boards) which allows direct connect to usb port. either way the chip must be flashed with isp first.

personally i do not use serial boot for attiny or mega avr. always isp for me because its simpler, faster, and easier. if you have uno or other arduino board it can be changed into an isp programmer with ardunio-as-isp sketch. otherwise usbasp type is required.

google is your friend.

Thx for your help John,

about google… there is where I’ve got lost … too many stuff!! Good thing I’ve an Arduino Uno R3, and will use it meanwile .

Thanks again,

lol. yes, sometimes google is your enemy.

i think you are in good shape. arduino-as-isp will save the day.

Thx John

one last question :-[

will this be any good ?


yes, that is my favorite model of usbasp. very expensive seller though. more info and maybe better ebay links here:

i always tell people these are so cheap always buy more than one.

I've done a few V-USB projects in my blog:


Have fun,


Thanks Ray, lot's of info there will have a look at.

so at the end what shall/can I do with this USB-TTL CP2102 ? just let it sit in the bin? :slight_smile:

usb/serial dongles are very useful. they are just about the only way to communicate with a pc. debugging and transfer of data are just a couple important applications. most people also use it to load programs although as mentioned i prefer isp (usbasp) for that. i think once you learn avr and arduino it will not end up in the bin.