A really cool LED matrix display - can be a killer dissplay+serial communication

Projects General Guidance
1

I got $10 "name badge" which I can connect to the computer using a USB cable and Prolific USB-serial adapter, and, using the provided software, I can have it display 120 chars scrolling message.

I used a serial monitor and figured out the protocol it is using to upload the text. Also wrote a short tool to send my own text. Now, I would like to have the Arduino send text to it using software serial.

So my question is: When I connect the Prolific adapter, I get a serial port on my PC. The cable from the adapter is a to the LED display is a USB cable. Can I assume that the D+ and D- pins in the USB cable are the serial Tx and Rx? Can I just take those two pins and connect them to my Arduino's digital pins and use the software serial library?

2

You can see it in action here:

Some pictures:

700×737 86.2 KB

3

szangvil:
So my question is: When I connect the Prolific adapter, I get a serial port on my PC. The cable from the adapter is a to the LED display is a USB cable. Can I assume that the D+ and D- pins in the USB cable are the serial Tx and Rx? Can I just take those two pins and connect them to my Arduino's digital pins and use the software serial library?

Not by about a million miles - USB doesn't work anything like that.

If you're lucky, you might find a USB-to-serial converter inside the device and be able to tap in to the serial output. If it uses the same signal levels as your Arduino you could potentially (sorry) connect your Arduino's software serial output to that point. This is analogous to connecting your Arduino's Rx andTx pins to another Arduino instead of using the USB interface.

4

I'm confused by your description of the cables, and how they were connected, but it sounds like the connection could be TTL serial. In that case you could use a serial-USB adapter. Someone successfully and quite completely hacked what appears to be a similar display (the original is French): http://translate.google.com/translate?hl=en&sl=auto&tl=en&u=http%3A%2F%2Fwww.digitalspirit.org%2Fwiki%2Fprojets%2Fledmatrixhacking

Take a look at the page and let us know if your badge has the same basic construction.

5

The display has a micro usb port. That connects to one side of the Prolific USB-Serial adapter with a USB cable. The other side of the Prolific adapter has a standard male USB which connects directly to the PC.

So I was thinking that the output of Prolific adapter is actually a serial connection "masked" in a USB cable.

6

A few minutes with an oscilloscope would confirm the signals.

7

The French guy who produced the web site I linked concluded the same t hing: the "usb" connection to the display is actually a TTL serial connection. You probably have the same basic device, which is pretty ingenious (as was his teardown). Do take a look at that link!

8

Thank you!

9

I have a project that I use a $5 USB / TTL converter to send from my embeded 328 board to a PC via usb.

I used the Prolific driver, and it works fine.

Just make sure it is the TTL and not RS232 which has high voltage levels.