CP2102 Breakout Board - TTL or RS232?

Archive New Product Ideas
1

Looking at the breakout board for the CP2102 -

http://www.sparkfun.com/commerce/produc … ts_id=8531

Is the serial side TTL or RS-232? The first paragraph -

The μUSB-MB5 is a USB to serial (TTL) converter which is simple, cost effective, very small and easy to use.

makes it sound like is is TTL levels, but the second -

The μUSB-MB5 makes an easy USB-Serial interface, so you can easily create USB to RS-232 converters.

makes it sound like it is RS-232 levels, then the final line

Please note: The TX and RX signal levels are between 0.0 Volts and 3.3 Volts.

makes it sound like TTL levels again, because 0V isn’t a valid RS-232 level.

The image seem to show it it pretty much just a USB socket and the CP2102 IC. Looking at the datasheet for the CP2102, it says

Royalty-free Virtual COM Port (VCP) device drivers provided by Silicon Laboratories allow a CP2102-based product to appear as a COM port to PC applications. The CP2102 UART interface implements all RS-232 signals, including control and handshaking signals, so existing system firmware does not need to be modified. In many existing RS-232 designs, all that is required to update the design from RS-232 to USB is to replace the RS-232 level-translator with the CP2102.

which is confusing in itself - it seems to say it “implements RS-232 signals” but then says you can replace the RS-232 level-translator with the CP2102

Hopefully someone can clear this up for me - does the CP2102 output TTL or RS-232 signals? I also suggest that SparkFun explicitly state is on the product’s page!

Thanks heaps

Alex

2

The primary purpose of this breakout board is to interface your PC to a micro controller. It is the USB version of a RS-232 level converter board to interface with a controller. The breakout board plugs into a USB port in your computer and the driver software for the computer implements TX, RX, CTS, RTS, and DTR. The board makes these signals available at 0v and 3.3v logic levels which are NOT the +/- RS-232 levels or strictly TTL (0v/5v) levels either. The data sheet implies that the board may be 5v logic level friendly (based on figure 2), but nothing is explicitly mentioned. It would be best to contact 4dSystems to make sure that the board can handle 0/5v levels.

3

Cool, thanks.

I guess if it’s primary purpose is to hook up to a microcontroller, it’s most likely TTL level.

It’s not like it can be a bit of both though - TTL and RS-232 are inverted - i.e. ‘HIGH’ on RS-232 is logic 0, but on TTL it’s logic 1.

Will contact manufacturer.

Thanks again

Alex

4

There are cheaper ways to go, but if you were looking to use this board as a USB to RS-232 converter, you can to add a level converter chip to get the RS-232 levels while letting the breakout board handle the USB stuff:

http://www.sparkfun.com/commerce/produc … cts_id=316

5

Alex, if you hear back from the 4DSystems, can you post if the part is safe to use with 5v signals? I have one that I’d like to use at 5V.