USB-TTL cable 3.3V or 5V?

Hi guys,

Any ideas what the advantages and disadvantages are of a 3.3V USB to TTL cable over a 5V USB to TTL cable, specifically for use with the motherboard V1.2?

Thanks...

afaik motherboard runs at 5v

The 5v cable can also be used via bit banging to program raw AVR chips to get them ready for use with the Arduino IDE.

i thought usb spec was for 5v signals ?

It is but there are 2 variants of the USB to RS232 serial cable 1 for 5v chips and 1 for 3.3v chips.

If you're prepared to put up with 3.3v you can hack a Nokia CA-42 data cable. There about £2 or $3

In order NOT to blow any I/O on your motherboard, use the power supply voltage of the processor. So if your processor is powered with 5V, use 5V. If it is 3.3V, use 3.3V.
If you use the ICL3221 you can use both voltages.
In case you need a ready made RS232-TTL converter, check www.tildesign.nl/rs232.htm for a converter, datasheet of the ICL3221 and a schematic of the converter.

Have fun !

"RS232" should mean +/-12V serial
"TTL" should mean 0-5V serial
Is there a term that implies 0-3.3V serial?

JohnWasser Wrote:
-------------------------------------------------------
> "RS232" should mean +/-12V serial
> "TTL" should mean 0-5V serial
> Is there a term that implies 0-3.3V serial?


Technically TTL is 5v, but many modern microcontrollers operate at 3.3v not 5, hence the 2 different types.

I beleive TTL was used because its convenient, changing the context to be TTL meaning ic output drive level.

3.3v is technically LVTTL.