Problem with my serial interface/blackfin camera

[Sarah21]

Regarding the breadboard USB from this link http://www.smileymicros.com/download/VSPCB/Breadboard%20USB%20Quick%20Start%20Guide.pdf
I started using it to test my blackfin camera and I got problems with getting the camera output http://www.societyofrobots.com/robotforum/index.php?topic=13373.0

So I decided to test it alone with the oscilloscope to see whether it is sending and receiving or not.
 So I used the hyperTerminal program to send some characters, and when I sent “A” I got the binary related to it on the oscilloscope screen and so on.
When I sent “V” to the camera I got a response on the oscilloscope, it was a square signal with 3.1-3.2 pk-pk… so it is like the camera is responding to what I sent, but it doesn’t show in the computer,

Now I know that my breadboard USB is sending and receiving I couldn’t figure out why the response doesn’t show in the computer, whether as a version name or a camera output.

Am taking care of the hardware handshaking and sure about the breadboard USB connections.. Any ideas people??

[vinniewryan]

Hmm, does your square wave signal coming from the blackfin look like a clock signal or a data signal? Can you program a micro controller to send data on the USB rx pin to test that your USB is even able to receive correctly? If you can capture an image of the square signal coming from the blackfin with a reference to time, then we can see exactly what information the blackfin is sending. Is your blackfin set up for the right data interface? I see it has I2C, SPI, and UART.

[Sarah21]

Hi vinniewryan

It look like a data signal. Ya I already tried to program a micro controller to send data on the USB rx pin and I successfully got a char on the HyperTerminal. I will try to post later an image for the square signal.

Is your blackfin set up for the right data interface?

I don't know exactly what do you mean by that. But I connected the Rx and Tx with each other from each side.

[vinniewryan]

Okay so look at the facts; Your USB RX is able to receive characters, your camera is receiving and transmitting data, but your USB RX doesn't like the data it's receiving from the camera. This sounds like it's either a level problem, or a baud rate issue. Or, your USB RX hardware is looking for an 'INVERTED' RS-232 signal. You must be sure your camera is configured to use the right communication protocol. If your USB board is looking for RS-232 data but your camera is sending I2C data, then the USB board will never understand the data it's receiving.

It looks like your USB board can be used with both 5V and 3.3V levels but I'm unsure if you have to configure it for either level, and your blackfin device only works with 3.3V so that's the level you want to configure your USB board to. Also I couldn't find any baud info on the USB board so i'm not sure what baud rates it will work with, though a lot of USB-serial devices can auto-detect baud rates, so that's something to look into. Do you have a link to the data sheet for your blackfin camera? If I could see the data sheet I can be much more help.

Click here: http://www.smileymicros.com/download/VSPCB/Breadboard%20USB%20Quick%20Start%20Guide.pdf and take a look at page 4. There are wiring diagrams for both 5V and 3.3V operation. Are you set up for 3.3v correctly?

[Sarah21]

 Here is the picture I captured from the oscilloscope when I sent “V”:

I think it is a data signal …

Okay so look at the facts; Your USB RX is able to receive characters, your camera is receiving and transmitting data, but your USB RX doesn't like the data it's receiving from the camera. This sounds like it's either a level problem, or a baud rate issue. Or, your USB RX hardware is looking for an 'INVERTED' RS-232 signal.

What does an RS-232 signal has to do with my breadboard USB? This breadboard USB has the FTDI F232R chip which is a UART-USB driver. So it will take UART signal (TTL) and gives me a USB signal, right?

You must be sure your camera is configured to use the right communication protocol. If your USB board is looking for RS-232 data but your camera is sending I2C data, then the USB board will never understand the data it's receiving.

I am using the Tx and Rx from the UART port, Can I get an I2C signal from a UART port?

Do you have a link to the data sheet for your blackfin camera? If I could see the data sheet I can be much more help.

http://www.surveyor.com/blackfin/

There are wiring diagrams for both 5V and 3.3V operation. Are you set up for 3.3v correctly?

I was using the 5v connection, then today I tried the 3.3v connection and it is the same.

[rbtying]

Hey, OP: Just wondering, do you have the Rx on the blackfin connected to the Rx on the UART-USB?  You will probably need to switch them (Tx to Rx and Rx to Tx).  It would appear to fit your problem, as everything's working but you have no data.

[Soeren]

Hi,

Here is the picture I captured from the oscilloscope when I sent “V”:

I think it is a data signal …

It reads out 10011101101
It's a bit weird, in the sense that if there's 2 start bits and one stop bit, it translates to:
 10 0111 0110 1 (0x76),
not a "V" (which is 0x56), but a "v" (lower case). I don't know if that matters, since you consistently claims that you send "V".
Mind you, I am not at all familiar with the Blackfin and neither do I know if you were trying to see what came return, so what I say might not help at all.

Deciphering it as normal (i.e. 1 start bit), it should be a ";" (semi-colon 0x3B).
Knowing the added parameters and the timing really is an important key to precise interpretation.

Assuming you send "v" and have an extra bit leading, it all ads up to that your DTE seems to be working fine. but wasn't it the output from the cam that you wanted to examine?

Can I get an I2C signal from a UART port?

No, IIC is Synchronous Serial (i.e. a separate clock signal is used to clock data through), and you cannot get that through an Universal Asynchronous Receiver/Transmitter (which an UART is), that has got the timing ("clock") signal embedded in the data stream.