How To interface Pixy with pic microcontroller?

Mucit23 · April 17, 2018, 5:13am

Hi

I’m using the PicMicrocontroller. I want to comunicate Pixy with SPI line. But but I don’t know how to do.

This is Pixy Object block format.

Bytes 16-bit words Description

0, 1 0 sync (0xaa55)
2, 3 1 checksum (sum of all 16-bit words 2-6)
4, 5 2 signature number
6, 7 3 x center of object
8, 9 4 y center of object
10, 11 5 width of object
12, 13 6 height of object

How I read the Pixy? How will be process sequence?

Thank You

rmsanchez · April 17, 2018, 5:13am

Hi Ferhat,
Interfacing Pixy over SPI is pretty straightforward – just connect MOSI to MOSI and MISO to MISO. You don’t need to bother with slave select.

The rest is parsing the data stream. The Arduino library is a great place to start:

github.com

charmedlabs/pixy/blob/master/src/host/arduino/libraries/Pixy/TPixy.h

//
// begin license header
//
// This file is part of Pixy CMUcam5 or "Pixy" for short
//
// All Pixy source code is provided under the terms of the
// GNU General Public License v2 (http://www.gnu.org/licenses/gpl-2.0.html).
// Those wishing to use Pixy source code, software and/or
// technologies under different licensing terms should contact us at
// [email protected]. Such licensing terms are available for
// all portions of the Pixy codebase presented here.
//
// end license header
//
// This file is for defining the Block struct and the Pixy template class.
// (TPixy).  TPixy takes a communication link as a template parameter so that 
// all communication modes (SPI, I2C and UART) can share the same code.  
//

#ifndef _TPIXY_H

This file has been truncated. show original

But your first program should be looking for sync words (0xaa55) so you can separate the object blocks and verify that your communications (connections, SPI controller initialization on your PIC, etc) are all good.

thanks!

rmsanchez · April 17, 2018, 5:13am

Hi Ferhat,
We wrote this recently and it might help —

http://cmucam.org/projects/cmucam5/wiki/Porting_Guide