Seeking info on Esp-32 interface to OV7725 from Alex

[Mark Johnston]

Sorry to post to open board but this topic I feel is of value to others as well.

Alex:  You showed I think it was an OV7725 interface to the Esp-32 dev board.

You also shared an interesting depth sensor with maybe 4 or maybe more elements at the bottom of the black plastic thing on your small bot.

1) Please share a link or two that you found to be informative and have 'good' code for use of OV7725 with Esp-32 current sdk OR maybe it was a different OV camera but you claimed it was about $5-$6

There are several OV7725 projects and I wanted to avoid picking up some code from some bozo that I struggle with for days.   Thanks

2) What was the depth sensor technique and part you were talking about that was fairly cheap and at the bottom of the black plastic thing you had on your bot in front?

Thanks,

Mark Johnston

[Alex Sy]

Mark,

The OV7725 in esp32-cam-demo-master.zip is a good one that I used and works.  You do have to pay attention to wire lengths as it is finicky due to the short setup/hold times.  Note that it is captured only as a Y (luminance) only 320X240 gray scale image, since there is not much RAM in the ESP32.  I do not remember where I downloaded it from but google should find it.  I plan to also support an OV7670 (which is a much cheaper camera) when I have some time!!

As for the depth sensor, it uses a red (650nm) laser customized to project a horizontal line, then a monochrome camera (with 650nm filter) located 2 inches above it looks at where the laser line hits and because of the parallax, the reflected bright spot gives a representation of the distance.  After calibration of camera intrinsics, and transformation it gives an X,Y position of all the spots in front of camera.  The laser is red to make it more obvious what is being scanned, but you can also use an IR laser and equivalent filters (I have tried both 850 and 905nm IR lasers).  This can scan about 120 degrees at 25 scans per second so it can support real time "map" of the front of the robot.

The middle camera is a C328 type JPEG serial camera, which has a much higher quality than any of the new JPEG (MV500NK) serial cameras.  The problem is that they are now discontinued.  They can also provide raw images which is what I use so that the camera could allow the robot to follow lines, look for/track objects etc.  I would have used the OV7725 except that it uses a whole ton of I/O pins and that is in short supply on the ESP32.

The two side mounted tubes used to be an experiment of using IR remote type transmit and receivers modified to generate analog outputs to measure side distances, but they did not work well.  They were to help in a micro-mouse setup to keep track of side walls, but the 2D laser rangefinder can provide that data so that it can track the walls and keep itself parallel to it as well as look for gaps.

I will bring it in future meetings probably early next year.  Hopefully I will have had time to do more work on it.

Alex

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