Reading Jevois data into Python over USB

Question

Hi,

I am trying to read data using Serial-over-USB with PyUSB. (I would also happily accept any other answer that gets me this data in Python).

For my tests, I'm using the AR demo, which gives output of the type "T2 x y", (i.e., "T2 432 -234"). I am trying to get this string into Python so I can manipulate it there.

Using screen and connecting directly to the Jevois, I do see output in that format.

However, when I connect using PyUSB, I get a long string of numbers. 

Example: [0, 0, 110, 192, 0, 128, 43, 0, 117, 192, 15, 65, 64, 31, 48, 206, 64, 245, 66, 192, 103, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 117, 192, 15, 65, 0, 0, 0, 0, 164, 190, 66, 192, 112, 190, 66, 192, 136, 5, 7, 192, 88, 130, 36, 192, 0, 0, 0, 0, 248, 35, 5]

Specific questions:

• how many bytes should I read?
• how do I translate the bytes into a string that looks like "T2 432 -234"?

Thanks,

Miriam

Answer 1

Thanks for asking! We just posted a tutorial for that:

http://jevois.org/tutorials/UserParseSerial.html

This should provide you with a start which you can modify for your own use. Also see http://jevois.org/tutorials/UserColorTracking.html for Python code that sends commands to JeVois.

Comments

This is great, thanks! I have it mostly working!

The only small issue I'm having is that I can't get 'setpar serstyle Normal' to stick when I put it in initscript.config. The other things I put there do work.

setpar serout USB
setmapping2 YUYV 320 240 30.0 JeVois DemoArUco
streamon

I can run 'setpar serstyle Normal' in the serial terminal and that works.

---

The serstyle param is a parameter of the module, so just make sure you set it after you load the module with setmapping2. If you set it before setmapping2, the setting will be applied to the current module, but then setmapping2 will unload the current module and load fresh the module specified in the setmapping2. So indeed the setting would then be lost.

Answer 2

Simple answer - try using readline instead of read.

line = ser.readline()