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UART connection

Pixy Software
#1

Hi Pixy team,
I’m new to Pixy, and trying to connect it to a DAQ system using SR-232 port (or UART).
The word string looks weird though.

The word comes as:
W0: 0xAB55 (should be sync?)
W1: 0xABAA
W2: 0xFADA
W3: 0xFFFD
and so on…

Do you have any thought on why I don’t get the proper sync word? Also, when moving the object, neither word 3 or 4 changes (which should be x and y position).

The words between blocks are consistently 0xFFFF. I checked in the provided getWord() function and it seems like it should be 0x0000?

Is this something you have encountered before and do you have any suggestions on how to proceed?

Thanks!
Leo

#2

Hello Leo,
There have been several users with similar issues with UART communications, and they usually turn out to be issues with the UART fifo over-running. This seems especially likely if you are printing the data as you grab it.

http://cmucam.org/boards/9/topics/5568?r=5680#message-5680

You might try grabbing data and storing to RAM before you print. And/or slowing the baud-rate until you get things working.

Edward

#3

Hello Leo,

You can’t use the RS-232 port directly.

The communication of the CMUcam is UART.

The voltage level of the UART and the RS-232 is different.

It’s may the reason that why you can’t receive the correct data from the CMUcam.

Good luck

Jamie

#4

Hi Jamie,

You were absolutely right.
I connected a level converter, bringing up the signal voltage from 3.3V to 5V.
It works perfectly.

Thanks!
Leo